history-substring-search: update to upstream version 2019-05-12

Updates OMZ's copy to commit 0f80b8eb3368b46e5e573c1d91ae69eb095db3fb from zsh-users/zsh-history-substring-search

plugins/history-substring-search/README.md

@@ -1,25 +1,44 @@
-zsh-history-substring-search
+# zsh-history-substring-search
-==============================================================================
 
 This is a clean-room implementation of the [Fish shell][1]'s history search
-feature, where you can type in any part of any previously entered command
+feature, where you can type in any part of any command from history and then
-and press the UP and DOWN arrow keys to cycle through the matching commands.
+press chosen keys, such as the UP and DOWN arrows, to cycle through matches.
-You can also use K and J in VI mode or ^P and ^N in EMACS mode for the same.
 
-[1]: https://fishshell.com
+[1]: http://fishshell.com
-[2]: https://www.zsh.org/mla/users/2009/msg00818.html
+[2]: http://www.zsh.org/mla/users/2009/msg00818.html
-[3]: https://sourceforge.net/projects/fizsh/
+[3]: http://sourceforge.net/projects/fizsh/
-[4]: https://github.com/ohmyzsh/ohmyzsh/pull/215
+[4]: https://github.com/robbyrussell/oh-my-zsh/pull/215
 [5]: https://github.com/zsh-users/zsh-history-substring-search
 [6]: https://github.com/zsh-users/zsh-syntax-highlighting
 
-------------------------------------------------------------------------------
+
 Requirements
 ------------------------------------------------------------------------------
 
 * [ZSH](http://zsh.sourceforge.net) 4.3 or newer
 
+Install
 ------------------------------------------------------------------------------
+
+Using the [Homebrew]( https://brew.sh ) package manager:
+
+    brew install zsh-history-substring-search
+    echo 'source /usr/local/share/zsh-history-substring-search/zsh-history-substring-search.zsh' >> ~/.zshrc
+
+Using [Oh-my-zsh](https://github.com/robbyrussell/oh-my-zsh):
+
+1. Clone this repository in oh-my-zsh's plugins directory:
+
+        git clone https://github.com/zsh-users/zsh-history-substring-search ${ZSH_CUSTOM:-~/.oh-my-zsh/custom}/plugins/zsh-history-substring-search
+
+2. Activate the plugin in `~/.zshrc`:
+
+        plugins=( [plugins...] history-substring-search)
+
+3. Source `~/.zshrc`  to take changes into account:
+
+        source ~/.zshrc
+
 Usage
 ------------------------------------------------------------------------------
 
@@ -33,117 +52,147 @@ Usage
         % source zsh-syntax-highlighting.zsh
         % source zsh-history-substring-search.zsh
 
-2.  Bind keyboard shortcuts to this script's functions:
+2.  Bind keyboard shortcuts to this script's functions.
 
-        # bind UP and DOWN arrow keys
+    Users typically bind their UP and DOWN arrow keys to this script, thus:
-        zmodload zsh/terminfo
+    * Run `cat -v` in your favorite terminal emulator to observe key codes.
-        bindkey "$terminfo[kcuu1]" history-substring-search-up
+      (**NOTE:** In some cases, `cat -v` shows the wrong key codes.  If the
-        bindkey "$terminfo[kcud1]" history-substring-search-down
+      key codes shown by `cat -v` don't work for you, press `<C-v><UP>` and
+      `<C-v><DOWN>` at your ZSH command line prompt for correct key codes.)
+    * Press the UP arrow key and observe what is printed in your terminal.
+    * Press the DOWN arrow key and observe what is printed in your terminal.
+    * Press the Control and C keys simultaneously to terminate the `cat -v`.
+    * Use your observations from the previous steps to create key bindings.
+      For example, if you observed `^[[A` for UP and `^[[B` for DOWN, then:
 
-        # bind UP and DOWN arrow keys (compatibility fallback
+          bindkey '^[[A' history-substring-search-up
-        # for Ubuntu 12.04, Fedora 21, and MacOSX 10.9 users)
+          bindkey '^[[B' history-substring-search-down
-        bindkey '^[[A' history-substring-search-up
-        bindkey '^[[B' history-substring-search-down
 
-        # bind P and N for EMACS mode
+      However, if the observed values don't work, you can try using terminfo:
-        bindkey -M emacs '^P' history-substring-search-up
-        bindkey -M emacs '^N' history-substring-search-down
 
-        # bind k and j for VI mode
+          bindkey "$terminfo[kcuu1]" history-substring-search-up
-        bindkey -M vicmd 'k' history-substring-search-up
+          bindkey "$terminfo[kcud1]" history-substring-search-down
-        bindkey -M vicmd 'j' history-substring-search-down
+
+      You might also want to bind the Control-P/N keys for use in EMACS mode:
+
+          bindkey -M emacs '^P' history-substring-search-up
+          bindkey -M emacs '^N' history-substring-search-down
+
+      You might also want to bind the `k` and `j` keys for use in VI mode:
+
+          bindkey -M vicmd 'k' history-substring-search-up
+          bindkey -M vicmd 'j' history-substring-search-down
 
 3.  Type any part of any previous command and then:
 
-    * Press the UP arrow key to select the nearest command that (1) contains
+    * Press the `history-substring-search-up` key, which was configured in
-      your query and (2) is older than the current command in the command
+      step 2 above, to select the nearest command that (1) contains your query
-      history.
+      and (2) is also older than the current command in your command history.
 
-    * Press the DOWN arrow key to select the nearest command that (1)
+    * Press the `history-substring-search-down` key, which was configured in
-      contains your query and (2) is newer than the current command in the
+      step 2 above, to select the nearest command that (1) contains your query
-      command history.
+      and (2) is also newer than the current command in your command history.
 
-    * Press ^U (the Control and U keys simultaneously) to abort the search.
+    * Press `^U` the Control and U keys simultaneously to abort the search.
 
 4.  If a matching command spans more than one line of text, press the LEFT
     arrow key to move the cursor away from the end of the command, and then:
 
-    * Press the UP arrow key to move the cursor to the line above.  When the
+    * Press the `history-substring-search-up` key, which was configured in
-      cursor reaches the first line of the command, pressing the UP arrow
+      step 2 above, to move the cursor to the line above the cursored line.
-      key again will cause this script to perform another search.
+      When the cursor reaches the first line of the command, pressing the
+      `history-substring-search-up` key again will cause this script to
+      perform another search.
+
+    * Press the `history-substring-search-down` key, which was configured in
+      step 2 above, to move the cursor to the line below the cursored line.
+      When the cursor reaches the last line of the command, pressing the
+      `history-substring-search-down` key, which was configured in step 2
+      above, again will cause this script to perform another search.
 
-    * Press the DOWN arrow key to move the cursor to the line below.  When
-      the cursor reaches the last line of the command, pressing the DOWN
-      arrow key again will cause this script to perform another search.
 
-------------------------------------------------------------------------------
 Configuration
 ------------------------------------------------------------------------------
 
 This script defines the following global variables. You may override their
 default values only after having loaded this script into your ZSH session.
 
-* HISTORY_SUBSTRING_SEARCH_HIGHLIGHT_FOUND is a global variable that defines
+* `HISTORY_SUBSTRING_SEARCH_HIGHLIGHT_FOUND` is a global variable that defines
   how the query should be highlighted inside a matching command. Its default
   value causes this script to highlight using bold, white text on a magenta
   background. See the "Character Highlighting" section in the zshzle(1) man
   page to learn about the kinds of values you may assign to this variable.
 
-* HISTORY_SUBSTRING_SEARCH_HIGHLIGHT_NOT_FOUND is a global variable that
+* `HISTORY_SUBSTRING_SEARCH_HIGHLIGHT_NOT_FOUND` is a global variable that
   defines how the query should be highlighted when no commands in the
   history match it. Its default value causes this script to highlight using
   bold, white text on a red background. See the "Character Highlighting"
   section in the zshzle(1) man page to learn about the kinds of values you
   may assign to this variable.
 
-* HISTORY_SUBSTRING_SEARCH_GLOBBING_FLAGS is a global variable that defines
+* `HISTORY_SUBSTRING_SEARCH_GLOBBING_FLAGS` is a global variable that defines
   how the command history will be searched for your query. Its default value
   causes this script to perform a case-insensitive search. See the "Globbing
   Flags" section in the zshexpn(1) man page to learn about the kinds of
   values you may assign to this variable.
 
-To always receive _unique_ search results, use `setopt HIST_IGNORE_ALL_DUPS`.
+* `HISTORY_SUBSTRING_SEARCH_FUZZY` is a global variable that defines
-Alternatively, use `setopt HIST_FIND_NO_DUPS` which makes this plugin skip
+  how the command history will be searched for your query. If set to a non-empty
-duplicate _adjacent_ search results as you cycle through them---however, this
+  value, causes this script to perform a fuzzy search by words, matching in
-does not guarantee that search results are unique: if your search results were
+  given order e.g. `ab c` will match `*ab*c*`
-"Dog", "Dog", "HotDog", "Dog", then cycling them gives "Dog", "HotDog", "Dog".
+
-Notice that the "Dog" search result appeared twice as you cycled through them!
+* `HISTORY_SUBSTRING_SEARCH_ENSURE_UNIQUE` is a global variable that defines
-If you wish to avoid this limitation, then use `setopt HIST_IGNORE_ALL_DUPS`.
+  whether all search results returned are _unique_. If set to a non-empty
+  value, then only unique search results are presented. This behaviour is off
+  by default. An alternative way to ensure that search results are unique is
+  to use `setopt HIST_IGNORE_ALL_DUPS`. If this configuration variable is off
+  and `setopt HIST_IGNORE_ALL_DUPS` is unset, then `setopt HIST_FIND_NO_DUPS`
+  is still respected and it makes this script skip duplicate _adjacent_ search
+  results as you cycle through them, but this does not guarantee that search
+  results are unique: if your search results were "Dog", "Dog", "HotDog",
+  "Dog", then cycling them gives "Dog", "HotDog", "Dog". Notice that the "Dog"
+  search result appeared twice as you cycled through them. If you wish to
+  receive globally unique search results only once, then use this
+  configuration variable, or use `setopt HIST_IGNORE_ALL_DUPS`.
+
 
-------------------------------------------------------------------------------
 History
 ------------------------------------------------------------------------------
 
-This script was originally written by [Peter Stephenson][2], who published it
+* September 2009: [Peter Stephenson][2] originally wrote this script and it
-to the ZSH users mailing list (thereby making it public domain) in September
+  published to the zsh-users mailing list.
-2009. It was later revised by Guido van Steen and released under the BSD
-license (see below) as part of [the fizsh project][3] in January 2011.
 
-It was later extracted from fizsh release 1.0.1, refactored heavily, and
+* January 2011: Guido van Steen (@guidovansteen) revised this script and
-repackaged as both an [oh-my-zsh plugin][4] and as an independently loadable
+  released it under the 3-clause BSD license as part of [fizsh][3], the
-[ZSH script][5] by Suraj N. Kurapati in 2011.
+  Friendly Interactive ZSHell.
 
-It was [further developed][4] by Guido van Steen, Suraj N. Kurapati, Sorin
+* January 2011: Suraj N. Kurapati (@sunaku) extracted this script from
-Ionescu, and Vincent Guerci in 2011.
+  [fizsh][3] 1.0.1, refactored it heavily, and finally repackaged it as an
+  [oh-my-zsh plugin][4] and as an independently loadable [ZSH script][5].
+
+* July 2011: Guido van Steen, Suraj N. Kurapati, and Sorin Ionescu
+  (@sorin-ionescu) [further developed it][4] with Vincent Guerci (@vguerci).
+
+* March 2016: Geza Lore (@gezalore) greatly refactored it in pull request #55.
 
 ------------------------------------------------------------------------------
 Oh My Zsh Distribution Notes
 ------------------------------------------------------------------------------
 
-What you are looking at now is Oh My Zsh's repackaging of zsh-history-substring-search
+What you are looking at now is Oh My Zsh's repackaging of zsh-history-substring-search 
 as an OMZ module inside the Oh My Zsh distribution.
 
-The upstream repo, zsh-users/zsh-history-substring-search, can be found on GitHub at
+The upstream repo, zsh-users/zsh-history-substring-search, can be found on GitHub at 
 https://github.com/zsh-users/zsh-history-substring-search.
 
 This downstream copy was last updated from the following upstream commit:
 
-  SHA:          2c295432175990c1bb4e90bc13f609daa67a25d6
+  SHA:          0f80b8eb3368b46e5e573c1d91ae69eb095db3fb
-  Commit date:  2015-09-28 10:47:34 -0700
+  Commit date:  2019-05-12 17:35:54 -0700
 
 Everything above this section is a copy of the original upstream's README, so things
 may differ slightly when you're using this inside OMZ. In particular, you do not
-need to set up key bindings for the up and down arrows yourself in `~/.zshrc`; the OMZ
+need to set up key bindings for the up and down arrows yourself in `~/.zshrc`; the OMZ 
 plugin does that for you. You may still want to set up additional emacs- or vi-specific
 bindings as mentioned above.
 

plugins/history-substring-search/history-substring-search.plugin.zsh

@@ -1,20 +1,9 @@
-# This file integrates the zsh-history-substring-search script into oh-my-zsh.
+0=${(%):-%N}
-
+source ${0:A:h}/zsh-history-substring-search.zsh
-source "${0:r:r}.zsh"
-
-if test "$CASE_SENSITIVE" = true; then
-  unset HISTORY_SUBSTRING_SEARCH_GLOBBING_FLAGS
-fi
-
-if test "$DISABLE_COLOR" = true; then
-  unset HISTORY_SUBSTRING_SEARCH_HIGHLIGHT_FOUND
-  unset HISTORY_SUBSTRING_SEARCH_HIGHLIGHT_NOT_FOUND
-fi
 
 
 # Bind terminal-specific up and down keys
-# Bind in both emacs and vi modes so it works in both, and is not
+
-# sensitive to whether this is loaded before or after the vi-mode plugin
 if [[ -n "$terminfo[kcuu1]" ]]; then
   bindkey -M emacs "$terminfo[kcuu1]" history-substring-search-up
   bindkey -M viins "$terminfo[kcuu1]" history-substring-search-up

plugins/history-substring-search/history-substring-search.zsh

@@ -6,6 +6,8 @@
 # Copyright (c) 2011 Suraj N. Kurapati
 # Copyright (c) 2011 Sorin Ionescu
 # Copyright (c) 2011 Vincent Guerci
+# Copyright (c) 2016 Geza Lore
+# Copyright (c) 2017 Bengt Brodersen
 # All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
@@ -38,12 +40,30 @@
 ##############################################################################
 
 #-----------------------------------------------------------------------------
-# configuration variables
+# declare global configuration variables
 #-----------------------------------------------------------------------------
 
-HISTORY_SUBSTRING_SEARCH_HIGHLIGHT_FOUND='bg=magenta,fg=white,bold'
+typeset -g HISTORY_SUBSTRING_SEARCH_HIGHLIGHT_FOUND='bg=magenta,fg=white,bold'
-HISTORY_SUBSTRING_SEARCH_HIGHLIGHT_NOT_FOUND='bg=red,fg=white,bold'
+typeset -g HISTORY_SUBSTRING_SEARCH_HIGHLIGHT_NOT_FOUND='bg=red,fg=white,bold'
-HISTORY_SUBSTRING_SEARCH_GLOBBING_FLAGS='i'
+typeset -g HISTORY_SUBSTRING_SEARCH_GLOBBING_FLAGS='i'
+typeset -g HISTORY_SUBSTRING_SEARCH_ENSURE_UNIQUE=''
+typeset -g HISTORY_SUBSTRING_SEARCH_FUZZY=''
+
+#-----------------------------------------------------------------------------
+# declare internal global variables
+#-----------------------------------------------------------------------------
+
+typeset -g BUFFER MATCH MBEGIN MEND CURSOR
+typeset -g _history_substring_search_refresh_display
+typeset -g _history_substring_search_query_highlight
+typeset -g _history_substring_search_result
+typeset -g _history_substring_search_query
+typeset -g -a _history_substring_search_query_parts
+typeset -g -a _history_substring_search_raw_matches
+typeset -g -i _history_substring_search_raw_match_index
+typeset -g -a _history_substring_search_matches
+typeset -g -i _history_substring_search_match_index
+typeset -g -A _history_substring_search_unique_filter
 
 #-----------------------------------------------------------------------------
 # the main ZLE widgets
@@ -180,62 +200,104 @@ _history-substring-search-begin() {
   _history_substring_search_query_highlight=
 
   #
-  # Continue using the previous $_history_substring_search_result by default,
+  # If the buffer is the same as the previously displayed history substring
-  # unless the current query was cleared or a new/different query was entered.
+  # search result, then just keep stepping through the match list. Otherwise
+  # start a new search.
   #
-  if [[ -z $BUFFER || $BUFFER != $_history_substring_search_result ]]; then
+  if [[ -n $BUFFER && $BUFFER == ${_history_substring_search_result:-} ]]; then
+    return;
+  fi
+
+  #
+  # Clear the previous result.
+  #
+  _history_substring_search_result=''
+
+  if [[ -z $BUFFER ]]; then
     #
-    # For the purpose of highlighting we will also keep
+    # If the buffer is empty, we will just act like up-history/down-history
-    # a version without doubly-escaped meta characters.
+    # in ZSH, so we do not need to actually search the history. This should
+    # speed things up a little.
+    #
+    _history_substring_search_query=
+    _history_substring_search_query_parts=()
+    _history_substring_search_raw_matches=()
+
+  else
+    #
+    # For the purpose of highlighting we keep a copy of the original
+    # query string.
     #
     _history_substring_search_query=$BUFFER
 
     #
-    # $BUFFER contains the text that is in the command-line currently.
+    # compose search pattern
-    # we put an extra "\\" before meta characters such as "\(" and "\)",
-    # so that they become "\\\(" and "\\\)".
     #
-    _history_substring_search_query_escaped=${BUFFER//(#m)[\][()|\\*?#<>~^]/\\$MATCH}
+    if [[ -n $HISTORY_SUBSTRING_SEARCH_FUZZY ]]; then
+      #
+      # `=` split string in arguments
+      #
+      _history_substring_search_query_parts=(${=_history_substring_search_query})
+    else
+      _history_substring_search_query_parts=(${==_history_substring_search_query})
+    fi
 
     #
-    # Find all occurrences of the search query in the history file.
+    # Escape and join query parts with wildcard character '*' as seperator
+    # `(j:CHAR:)` join array to string with CHAR as seperator
+    #
+    local search_pattern="*${(j:*:)_history_substring_search_query_parts[@]//(#m)[\][()|\\*?#<>~^]/\\$MATCH}*"
+
+    #
+    # Find all occurrences of the search pattern in the history file.
     #
     # (k) returns the "keys" (history index numbers) instead of the values
-    # (Oa) reverses the order, because (R) returns results reversed.
+    # (R) returns values in reverse older, so the index of the youngest
+    # matching history entry is at the head of the list.
     #
-    _history_substring_search_matches=(${(kOa)history[(R)(#$HISTORY_SUBSTRING_SEARCH_GLOBBING_FLAGS)*${_history_substring_search_query_escaped}*]})
+    _history_substring_search_raw_matches=(${(k)history[(R)(#$HISTORY_SUBSTRING_SEARCH_GLOBBING_FLAGS)${search_pattern}]})
+  fi
 
-    #
+  #
-    # Define the range of values that $_history_substring_search_match_index
+  # In order to stay as responsive as possible, we will process the raw
-    # can take: [0, $_history_substring_search_matches_count_plus].
+  # matches lazily (when the user requests the next match) to choose items
-    #
+  # that need to be displayed to the user.
-    _history_substring_search_matches_count=$#_history_substring_search_matches
+  # _history_substring_search_raw_match_index holds the index of the last
-    _history_substring_search_matches_count_plus=$(( _history_substring_search_matches_count + 1 ))
+  # unprocessed entry in _history_substring_search_raw_matches. Any items
-    _history_substring_search_matches_count_sans=$(( _history_substring_search_matches_count - 1 ))
+  # that need to be displayed will be added to
+  # _history_substring_search_matches.
+  #
+  # We use an associative array (_history_substring_search_unique_filter) as
+  # a 'set' data structure to ensure uniqueness of the results if desired.
+  # If an entry (key) is in the set (non-empty value), then we have already
+  # added that entry to _history_substring_search_matches.
+  #
+  _history_substring_search_raw_match_index=0
+  _history_substring_search_matches=()
+  _history_substring_search_unique_filter=()
 
-    #
+  #
-    # If $_history_substring_search_match_index is equal to
+  # If $_history_substring_search_match_index is equal to
-    # $_history_substring_search_matches_count_plus, this indicates that we
+  # $#_history_substring_search_matches + 1, this indicates that we
-    # are beyond the beginning of $_history_substring_search_matches.
+  # are beyond the end of $_history_substring_search_matches and that we
-    #
+  # have also processed all entries in
-    # If $_history_substring_search_match_index is equal to 0, this indicates
+  # _history_substring_search_raw_matches.
-    # that we are beyond the end of $_history_substring_search_matches.
+  #
-    #
+  # If $#_history_substring_search_match_index is equal to 0, this indicates
-    # If we have initially pressed "up" we have to initialize
+  # that we are beyond the beginning of $_history_substring_search_matches.
-    # $_history_substring_search_match_index to
+  #
-    # $_history_substring_search_matches_count_plus so that it will be
+  # If we have initially pressed "up" we have to initialize
-    # decreased to $_history_substring_search_matches_count.
+  # $_history_substring_search_match_index to 0 so that it will be
-    #
+  # incremented to 1.
-    # If we have initially pressed "down" we have to initialize
+  #
-    # $_history_substring_search_match_index to
+  # If we have initially pressed "down" we have to initialize
-    # $_history_substring_search_matches_count so that it will be increased to
+  # $_history_substring_search_match_index to 1 so that it will be
-    # $_history_substring_search_matches_count_plus.
+  # decremented to 0.
-    #
+  #
-    if [[ $WIDGET == history-substring-search-down ]]; then
+  if [[ $WIDGET == history-substring-search-down ]]; then
-       _history_substring_search_match_index=$_history_substring_search_matches_count
+     _history_substring_search_match_index=1
-    else
+  else
-      _history_substring_search_match_index=$_history_substring_search_matches_count_plus
+    _history_substring_search_match_index=0
-    fi
   fi
 }
 
@@ -255,16 +317,21 @@ _history-substring-search-end() {
   _zsh_highlight
 
   # highlight the search query inside the command line
-  if [[ -n $_history_substring_search_query_highlight && -n $_history_substring_search_query ]]; then
+  if [[ -n $_history_substring_search_query_highlight ]]; then
-    #
+    # highlight first matching query parts
-    # The following expression yields a variable $MBEGIN, which
+    local highlight_start_index=0
-    # indicates the begin position + 1 of the first occurrence
+    local highlight_end_index=0
-    # of _history_substring_search_query_escaped in $BUFFER.
+    local query_part
-    #
+    for query_part in $_history_substring_search_query_parts; do
-    : ${(S)BUFFER##(#m$HISTORY_SUBSTRING_SEARCH_GLOBBING_FLAGS)($_history_substring_search_query##)}
+      local escaped_query_part=${query_part//(#m)[\][()|\\*?#<>~^]/\\$MATCH}
-    local begin=$(( MBEGIN - 1 ))
+      # (i) get index of pattern
-    local end=$(( begin + $#_history_substring_search_query ))
+      local query_part_match_index="${${BUFFER:$highlight_start_index}[(i)(#$HISTORY_SUBSTRING_SEARCH_GLOBBING_FLAGS)${escaped_query_part}]}"
-    region_highlight+=("$begin $end $_history_substring_search_query_highlight")
+      if [[ $query_part_match_index -le ${#BUFFER:$highlight_start_index} ]]; then
+        highlight_start_index=$(( $highlight_start_index + $query_part_match_index ))
+        highlight_end_index=$(( $highlight_start_index + ${#query_part} ))
+        region_highlight+=("$(($highlight_start_index - 1)) $(($highlight_end_index - 1)) $_history_substring_search_query_highlight")
+      fi
+    done
   fi
 
   # For debugging purposes:
@@ -378,12 +445,143 @@ _history-substring-search-down-history() {
   return 1
 }
 
+_history_substring_search_process_raw_matches() {
+  #
+  # Process more outstanding raw matches and append any matches that need to
+  # be displayed to the user to _history_substring_search_matches.
+  # Return whether there were any more results appended.
+  #
+
+  #
+  # While we have more raw matches. Process them to see if there are any more
+  # matches that need to be displayed to the user.
+  #
+  while [[ $_history_substring_search_raw_match_index -lt $#_history_substring_search_raw_matches ]]; do
+    #
+    # Move on to the next raw entry and get its history index.
+    #
+    _history_substring_search_raw_match_index+=1
+    local index=${_history_substring_search_raw_matches[$_history_substring_search_raw_match_index]}
+
+    #
+    # If HISTORY_SUBSTRING_SEARCH_ENSURE_UNIQUE is set to a non-empty value,
+    # then ensure that only unique matches are presented to the user.
+    # When HIST_IGNORE_ALL_DUPS is set, ZSH already ensures a unique history,
+    # so in this case we do not need to do anything.
+    #
+    if [[ ! -o HIST_IGNORE_ALL_DUPS && -n $HISTORY_SUBSTRING_SEARCH_ENSURE_UNIQUE ]]; then
+      #
+      # Get the actual history entry at the new index, and check if we have
+      # already added it to _history_substring_search_matches.
+      #
+      local entry=${history[$index]}
+
+      if [[ -z ${_history_substring_search_unique_filter[$entry]} ]]; then
+        #
+        # This is a new unique entry. Add it to the filter and append the
+        # index to _history_substring_search_matches.
+        #
+        _history_substring_search_unique_filter[$entry]=1
+        _history_substring_search_matches+=($index)
+
+        #
+        # Indicate that we did find a match.
+        #
+        return 0
+      fi
+
+    else
+      #
+      # Just append the new history index to the processed matches.
+      #
+      _history_substring_search_matches+=($index)
+
+      #
+      # Indicate that we did find a match.
+      #
+      return 0
+    fi
+
+  done
+
+  #
+  # We are beyond the end of the list of raw matches. Indicate that no
+  # more matches are available.
+  #
+  return 1
+}
+
+_history-substring-search-has-next() {
+  #
+  # Predicate function that returns whether any more older matches are
+  # available.
+  #
+
+  if  [[ $_history_substring_search_match_index -lt $#_history_substring_search_matches ]]; then
+    #
+    # We did not reach the end of the processed list, so we do have further
+    # matches.
+    #
+    return 0
+
+  else
+    #
+    # We are at the end of the processed list. Try to process further
+    # unprocessed matches. _history_substring_search_process_raw_matches
+    # returns whether any more matches were available, so just return
+    # that result.
+    #
+    _history_substring_search_process_raw_matches
+    return $?
+  fi
+}
+
+_history-substring-search-has-prev() {
+  #
+  # Predicate function that returns whether any more younger matches are
+  # available.
+  #
+
+  if [[ $_history_substring_search_match_index -gt 1 ]]; then
+    #
+    # We did not reach the beginning of the processed list, so we do have
+    # further matches.
+    #
+    return 0
+
+  else
+    #
+    # We are at the beginning of the processed list. We do not have any more
+    # matches.
+    #
+    return 1
+  fi
+}
+
+_history-substring-search-found() {
+  #
+  # A match is available. The index of the match is held in
+  # $_history_substring_search_match_index
+  #
+  # 1. Make $BUFFER equal to the matching history entry.
+  #
+  # 2. Use $HISTORY_SUBSTRING_SEARCH_HIGHLIGHT_FOUND
+  #    to highlight the current buffer.
+  #
+  BUFFER=$history[$_history_substring_search_matches[$_history_substring_search_match_index]]
+  _history_substring_search_query_highlight=$HISTORY_SUBSTRING_SEARCH_HIGHLIGHT_FOUND
+}
+
 _history-substring-search-not-found() {
   #
-  # Nothing matched the search query, so put it back into the $BUFFER while
+  # No more matches are available.
-  # highlighting it accordingly so the user can revise it and search again.
+  #
+  # 1. Make $BUFFER equal to $_history_substring_search_query so the user can
+  #    revise it and search again.
+  #
+  # 2. Use $HISTORY_SUBSTRING_SEARCH_HIGHLIGHT_NOT_FOUND
+  #    to highlight the current buffer.
   #
-  _history_substring_search_old_buffer=$BUFFER
   BUFFER=$_history_substring_search_query
   _history_substring_search_query_highlight=$HISTORY_SUBSTRING_SEARCH_HIGHLIGHT_NOT_FOUND
 }
@@ -392,91 +590,84 @@ _history-substring-search-up-search() {
   _history_substring_search_refresh_display=1
 
   #
-  # Highlight matches during history-substring-up-search:
+  # Select history entry during history-substring-down-search:
   #
-  # The following constants have been initialized in
+  # The following variables have been initialized in
   # _history-substring-search-up/down-search():
   #
-  # $_history_substring_search_matches is the current list of matches
+  # $_history_substring_search_matches is the current list of matches that
-  # $_history_substring_search_matches_count is the current number of matches
+  # need to be displayed to the user.
-  # $_history_substring_search_matches_count_plus is the current number of matches + 1
-  # $_history_substring_search_matches_count_sans is the current number of matches - 1
   # $_history_substring_search_match_index is the index of the current match
+  # that is being displayed to the user.
   #
   # The range of values that $_history_substring_search_match_index can take
-  # is: [0, $_history_substring_search_matches_count_plus].  A value of 0
+  # is: [0, $#_history_substring_search_matches + 1].  A value of 0
-  # indicates that we are beyond the end of
+  # indicates that we are beyond the beginning of
   # $_history_substring_search_matches. A value of
-  # $_history_substring_search_matches_count_plus indicates that we are beyond
+  # $#_history_substring_search_matches + 1 indicates that we are beyond
-  # the beginning of $_history_substring_search_matches.
+  # the end of $_history_substring_search_matches and that we have also
+  # processed all entries in _history_substring_search_raw_matches.
+  #
+  # If $_history_substring_search_match_index equals
+  # $#_history_substring_search_matches and
+  # $_history_substring_search_raw_match_index is not greater than
+  # $#_history_substring_search_raw_matches, then we need to further process
+  # $_history_substring_search_raw_matches to see if there are any more
+  # entries that need to be displayed to the user.
   #
   # In _history-substring-search-up-search() the initial value of
-  # $_history_substring_search_match_index is
+  # $_history_substring_search_match_index is 0. This value is set in
-  # $_history_substring_search_matches_count_plus.  This value is set in
+  # _history-substring-search-begin(). _history-substring-search-up-search()
-  # _history-substring-search-begin().  _history-substring-search-up-search()
+  # will initially increment it to 1.
-  # will initially decrease it to $_history_substring_search_matches_count.
   #
-  if [[ $_history_substring_search_match_index -ge 2 ]]; then
-    #
-    # Highlight the next match:
-    #
-    # 1. Decrease the value of $_history_substring_search_match_index.
-    #
-    # 2. Use $HISTORY_SUBSTRING_SEARCH_HIGHLIGHT_FOUND
-    #    to highlight the current buffer.
-    #
-    (( _history_substring_search_match_index-- ))
-    BUFFER=$history[$_history_substring_search_matches[$_history_substring_search_match_index]]
-    _history_substring_search_query_highlight=$HISTORY_SUBSTRING_SEARCH_HIGHLIGHT_FOUND
 
-  elif [[ $_history_substring_search_match_index -eq 1 ]]; then
+  if [[ $_history_substring_search_match_index -gt $#_history_substring_search_matches ]]; then
     #
-    # We will move beyond the end of $_history_substring_search_matches:
+    # We are beyond the end of $_history_substring_search_matches. This
+    # can only happen if we have also exhausted the unprocessed matches in
+    # _history_substring_search_raw_matches.
     #
-    # 1. Decrease the value of $_history_substring_search_match_index.
+    # 1. Update display to indicate search not found.
-    #
-    # 2. Save the current buffer in $_history_substring_search_old_buffer,
-    #    so that it can be retrieved by
-    #    _history-substring-search-down-search() later.
-    #
-    # 3. Make $BUFFER equal to $_history_substring_search_query.
-    #
-    # 4. Use $HISTORY_SUBSTRING_SEARCH_HIGHLIGHT_NOT_FOUND
-    #    to highlight the current buffer.
-    #
-    (( _history_substring_search_match_index-- ))
-    _history-substring-search-not-found
-
-  elif [[ $_history_substring_search_match_index -eq $_history_substring_search_matches_count_plus ]]; then
-    #
-    # We were beyond the beginning of $_history_substring_search_matches but
-    # UP makes us move back to $_history_substring_search_matches:
-    #
-    # 1. Decrease the value of $_history_substring_search_match_index.
-    #
-    # 2. Restore $BUFFER from $_history_substring_search_old_buffer.
-    #
-    # 3. Use $HISTORY_SUBSTRING_SEARCH_HIGHLIGHT_FOUND
-    #    to highlight the current buffer.
-    #
-    (( _history_substring_search_match_index-- ))
-    BUFFER=$_history_substring_search_old_buffer
-    _history_substring_search_query_highlight=$HISTORY_SUBSTRING_SEARCH_HIGHLIGHT_FOUND
-
-  else
-    #
-    # We are at the beginning of history and there are no further matches.
     #
     _history-substring-search-not-found
     return
   fi
 
+  if _history-substring-search-has-next; then
+    #
+    # We do have older matches.
+    #
+    # 1. Move index to point to the next match.
+    # 2. Update display to indicate search found.
+    #
+    _history_substring_search_match_index+=1
+    _history-substring-search-found
+
+  else
+    #
+    # We do not have older matches.
+    #
+    # 1. Move the index beyond the end of
+    #    _history_substring_search_matches.
+    # 2. Update display to indicate search not found.
+    #
+    _history_substring_search_match_index+=1
+    _history-substring-search-not-found
+  fi
+
   #
   # When HIST_FIND_NO_DUPS is set, meaning that only unique command lines from
   # history should be matched, make sure the new and old results are different.
-  # But when HIST_IGNORE_ALL_DUPS is set, ZSH already ensures a unique history.
   #
-  if [[ ! -o HIST_IGNORE_ALL_DUPS && -o HIST_FIND_NO_DUPS && $BUFFER == $_history_substring_search_result ]]; then
+  # However, if the HIST_IGNORE_ALL_DUPS shell option, or
+  # HISTORY_SUBSTRING_SEARCH_ENSURE_UNIQUE is set, then we already have a
+  # unique history, so in this case we do not need to do anything.
+  #
+  if [[ -o HIST_IGNORE_ALL_DUPS || -n $HISTORY_SUBSTRING_SEARCH_ENSURE_UNIQUE ]]; then
+    return
+  fi
+
+  if [[ -o HIST_FIND_NO_DUPS && $BUFFER == $_history_substring_search_result ]]; then
     #
     # Repeat the current search so that a different (unique) match is found.
     #
@@ -488,92 +679,75 @@ _history-substring-search-down-search() {
   _history_substring_search_refresh_display=1
 
   #
-  # Highlight matches during history-substring-up-search:
+  # Select history entry during history-substring-down-search:
   #
-  # The following constants have been initialized in
+  # The following variables have been initialized in
   # _history-substring-search-up/down-search():
   #
-  # $_history_substring_search_matches is the current list of matches
+  # $_history_substring_search_matches is the current list of matches that
-  # $_history_substring_search_matches_count is the current number of matches
+  # need to be displayed to the user.
-  # $_history_substring_search_matches_count_plus is the current number of matches + 1
-  # $_history_substring_search_matches_count_sans is the current number of matches - 1
   # $_history_substring_search_match_index is the index of the current match
+  # that is being displayed to the user.
   #
   # The range of values that $_history_substring_search_match_index can take
-  # is: [0, $_history_substring_search_matches_count_plus].  A value of 0
+  # is: [0, $#_history_substring_search_matches + 1].  A value of 0
-  # indicates that we are beyond the end of
+  # indicates that we are beyond the beginning of
   # $_history_substring_search_matches. A value of
-  # $_history_substring_search_matches_count_plus indicates that we are beyond
+  # $#_history_substring_search_matches + 1 indicates that we are beyond
-  # the beginning of $_history_substring_search_matches.
+  # the end of $_history_substring_search_matches and that we have also
+  # processed all entries in _history_substring_search_raw_matches.
   #
   # In _history-substring-search-down-search() the initial value of
-  # $_history_substring_search_match_index is
+  # $_history_substring_search_match_index is 1. This value is set in
-  # $_history_substring_search_matches_count.  This value is set in
+  # _history-substring-search-begin(). _history-substring-search-down-search()
-  # _history-substring-search-begin().
+  # will initially decrement it to 0.
-  # _history-substring-search-down-search() will initially increase it to
-  # $_history_substring_search_matches_count_plus.
   #
-  if [[ $_history_substring_search_match_index -le $_history_substring_search_matches_count_sans ]]; then
-    #
-    # Highlight the next match:
-    #
-    # 1. Increase $_history_substring_search_match_index by 1.
-    #
-    # 2. Use $HISTORY_SUBSTRING_SEARCH_HIGHLIGHT_FOUND
-    #    to highlight the current buffer.
-    #
-    (( _history_substring_search_match_index++ ))
-    BUFFER=$history[$_history_substring_search_matches[$_history_substring_search_match_index]]
-    _history_substring_search_query_highlight=$HISTORY_SUBSTRING_SEARCH_HIGHLIGHT_FOUND
 
-  elif [[ $_history_substring_search_match_index -eq $_history_substring_search_matches_count ]]; then
+  if [[ $_history_substring_search_match_index -lt 1 ]]; then
     #
-    # We will move beyond the beginning of $_history_substring_search_matches:
+    # We are beyond the beginning of $_history_substring_search_matches.
     #
-    # 1. Increase $_history_substring_search_match_index by 1.
+    # 1. Update display to indicate search not found.
-    #
-    # 2. Save the current buffer in $_history_substring_search_old_buffer, so
-    #    that it can be retrieved by _history-substring-search-up-search()
-    #    later.
-    #
-    # 3. Make $BUFFER equal to $_history_substring_search_query.
-    #
-    # 4. Use $HISTORY_SUBSTRING_SEARCH_HIGHLIGHT_NOT_FOUND
-    #    to highlight the current buffer.
-    #
-    (( _history_substring_search_match_index++ ))
-    _history-substring-search-not-found
-
-  elif [[ $_history_substring_search_match_index -eq 0 ]]; then
-    #
-    # We were beyond the end of $_history_substring_search_matches but DOWN
-    # makes us move back to the $_history_substring_search_matches:
-    #
-    # 1. Increase $_history_substring_search_match_index by 1.
-    #
-    # 2. Restore $BUFFER from $_history_substring_search_old_buffer.
-    #
-    # 3. Use $HISTORY_SUBSTRING_SEARCH_HIGHLIGHT_FOUND
-    #    to highlight the current buffer.
-    #
-    (( _history_substring_search_match_index++ ))
-    BUFFER=$_history_substring_search_old_buffer
-    _history_substring_search_query_highlight=$HISTORY_SUBSTRING_SEARCH_HIGHLIGHT_FOUND
-
-  else
-    #
-    # We are at the end of history and there are no further matches.
     #
     _history-substring-search-not-found
     return
   fi
 
+  if _history-substring-search-has-prev; then
+    #
+    # We do have younger matches.
+    #
+    # 1. Move index to point to the previous match.
+    # 2. Update display to indicate search found.
+    #
+    _history_substring_search_match_index+=-1
+    _history-substring-search-found
+
+  else
+    #
+    # We do not have younger matches.
+    #
+    # 1. Move the index beyond the beginning of
+    #    _history_substring_search_matches.
+    # 2. Update display to indicate search not found.
+    #
+    _history_substring_search_match_index+=-1
+    _history-substring-search-not-found
+  fi
+
   #
   # When HIST_FIND_NO_DUPS is set, meaning that only unique command lines from
   # history should be matched, make sure the new and old results are different.
-  # But when HIST_IGNORE_ALL_DUPS is set, ZSH already ensures a unique history.
   #
-  if [[ ! -o HIST_IGNORE_ALL_DUPS && -o HIST_FIND_NO_DUPS && $BUFFER == $_history_substring_search_result ]]; then
+  # However, if the HIST_IGNORE_ALL_DUPS shell option, or
+  # HISTORY_SUBSTRING_SEARCH_ENSURE_UNIQUE is set, then we already have a
+  # unique history, so in this case we do not need to do anything.
+  #
+  if [[ -o HIST_IGNORE_ALL_DUPS || -n $HISTORY_SUBSTRING_SEARCH_ENSURE_UNIQUE ]]; then
+    return
+  fi
+
+  if [[ -o HIST_FIND_NO_DUPS && $BUFFER == $_history_substring_search_result ]]; then
     #
     # Repeat the current search so that a different (unique) match is found.
     #