Add option for matching on previous command.

Setting ZSH_AUTOSUGGEST_MATCH_PREV_CMD will enable the plug-in to be a
bit more context aware when generating the suggestion, by matching the
previously executed command against the command executed before the
preferred suggestion. See src/config.zsh for an example.

Also added testing for the suggestion computation.

script/test.zsh

@@ -3,12 +3,151 @@
 SCRIPT_DIR=$(dirname "$0")
 TEST_DIR=$SCRIPT_DIR/../test
 DIST_DIR=$SCRIPT_DIR/../
+TMPHIST_FILE=/tmp/zsh-autosuggestions-test-tmp-hist
 
 # Use stub.sh for stubbing/mocking
 source $TEST_DIR/stub-1.0.2.sh
 
 source $DIST_DIR/zsh-autosuggestions.zsh
 
+#--------------------------------------------------------------------#
+# Suggestions                                                        #
+#--------------------------------------------------------------------#
+
+testSuggestionSimple() {
+	HISTSIZE=0  # Clear history
+	HISTSIZE=10
+
+	cat > $TMPHIST_FILE <<-EOH
+		one
+		two
+		three
+		four
+		five
+	EOH
+	echo >> $TMPHIST_FILE
+
+	fc -R $TMPHIST_FILE
+
+	rm $TMPHIST_FILE
+
+	unset ZSH_AUTOSUGGEST_MATCH_PREV_CMD
+
+	assertEquals \
+		"Did not pick correct suggestion for prefix 'garbage'" \
+		"" \
+		"$(_zsh_autosuggest_suggestion garbage)"
+
+	assertEquals \
+		"Did not pick correct suggestion for prefix 'o'" \
+		"one" \
+		"$(_zsh_autosuggest_suggestion o)"
+
+	assertEquals \
+		"Did not pick correct suggestion for prefix 't'" \
+		"three" \
+		"$(_zsh_autosuggest_suggestion t)"
+
+	assertEquals \
+		"Did not pick correct suggestion for prefix 'tw'" \
+		"two" \
+		"$(_zsh_autosuggest_suggestion tw)"
+
+	assertEquals \
+		"Did not pick correct suggestion for prefix 'f'" \
+		"five" \
+		"$(_zsh_autosuggest_suggestion f)"
+
+	assertEquals \
+		"Did not pick correct suggestion for prefix 'fo'" \
+		"four" \
+		"$(_zsh_autosuggest_suggestion fo)"
+}
+
+testSuggestionMatchPrevCmd() {
+	HISTSIZE=0  # Clear history
+	HISTSIZE=10
+
+	cat > $TMPHIST_FILE <<-EOH
+		one
+		two
+		three
+		four
+		five
+	EOH
+	echo >> $TMPHIST_FILE
+
+	fc -R $TMPHIST_FILE
+
+	rm $TMPHIST_FILE
+
+	ZSH_AUTOSUGGEST_MATCH_PREV_CMD=1
+
+	stub_and_echo _zsh_autosuggest_prev_cmd "one"
+
+	assertEquals \
+		"Did not pick correct suggestion for prefix 'garbage' after 'one'" \
+		"" \
+		"$(_zsh_autosuggest_suggestion garbage)"
+
+	assertEquals \
+		"Did not pick correct suggestion for prefix 'o' after 'one'" \
+		"one" \
+		"$(_zsh_autosuggest_suggestion o)"
+
+	assertEquals \
+		"Did not pick correct suggestion for prefix 't' after 'one'" \
+		"two" \
+		"$(_zsh_autosuggest_suggestion t)"
+
+	assertEquals \
+		"Did not pick correct suggestion for prefix 'th' after 'one'" \
+		"three" \
+		"$(_zsh_autosuggest_suggestion th)"
+
+	assertEquals \
+		"Did not pick correct suggestion for prefix 'f' after 'one'" \
+		"five" \
+		"$(_zsh_autosuggest_suggestion f)"
+
+	assertEquals \
+		"Did not pick correct suggestion for prefix 'fo' after 'one" \
+		"four" \
+		"$(_zsh_autosuggest_suggestion fo)"
+
+	stub_and_echo _zsh_autosuggest_prev_cmd "two"
+
+	assertEquals \
+		"Did not pick correct suggestion for prefix 'garbage' after 'two'" \
+		"" \
+		"$(_zsh_autosuggest_suggestion garbage)"
+
+	assertEquals \
+		"Did not pick correct suggestion for prefix 'o' after 'two'" \
+		"one" \
+		"$(_zsh_autosuggest_suggestion o)"
+
+	assertEquals \
+		"Did not pick correct suggestion for prefix 't' after 'two'" \
+		"three" \
+		"$(_zsh_autosuggest_suggestion t)"
+
+	assertEquals \
+		"Did not pick correct suggestion for prefix 'tw' after 'two'" \
+		"two" \
+		"$(_zsh_autosuggest_suggestion tw)"
+
+	assertEquals \
+		"Did not pick correct suggestion for prefix 'f' after 'two'" \
+		"five" \
+		"$(_zsh_autosuggest_suggestion f)"
+
+	assertEquals \
+		"Did not pick correct suggestion for prefix 'fo' after 'two" \
+		"four" \
+		"$(_zsh_autosuggest_suggestion fo)"
+}
+
 #--------------------------------------------------------------------#
 # Highlighting                                                       #
 #--------------------------------------------------------------------#

src/config.zsh

@@ -8,6 +8,18 @@
 # More info: http://zsh.sourceforge.net/Doc/Release/Zsh-Line-Editor.html#Zle-Widgets
 ZSH_AUTOSUGGEST_HIGHLIGHT_STYLE='fg=8'
 
+# Set this to enable matching the history entry preceding the suggestion
+# against the previously executed command.
+# For example, if your have just executed:
+#   pwd
+#   ls foo
+#   ls bar
+#   pwd
+# And then you start typing 'ls', then the suggestion will be 'ls foo',
+# rather than 'ls bar', as your most recently executed command (pwd)
+# was succeeded by 'ls foo' on it's previous invocation.
+unset ZSH_AUTOSUGGEST_MATCH_PREV_CMD
+
 # Prefix to use when saving original versions of bound widgets
 ZSH_AUTOSUGGEST_ORIGINAL_WIDGET_PREFIX=autosuggest-orig-
 

src/suggestion.zsh

@@ -3,16 +3,44 @@
 # Suggestion                                                         #
 #--------------------------------------------------------------------#
 
+# Get the peviously executed command (hookable for testing)
+_zsh_autosuggest_prev_cmd() {
+	echo -E "${history[$((HISTCMD-1))]}"
+}
+
 # Get a suggestion from history that matches a given prefix
 _zsh_autosuggest_suggestion() {
 	local prefix="$(_zsh_autosuggest_escape_command_prefix "$1")"
 
-	# Get all history items (reversed) that match pattern $prefix*
+	# Get all history event numbers (reversed) that correspond to history
-	local history_matches
+	# entries that match pattern $prefix*
-	history_matches=(${(j:\0:s:\0:)history[(R)$prefix*]})
+	local history_match_keys=(${(k)history[(R)$prefix*]})
 
-	# Echo the first item that matches
+	# By default we use the first history number (most recent history entry)
-	echo -E "$history_matches[1]"
+	local history_key="$history_match_keys[1]"
+
+	# If matching on the previous command is enabled ...
+	if (( ${+ZSH_AUTOSUGGEST_MATCH_PREV_CMD} )); then
+		# Get the previously executed command
+		local prev_cmd=$(_zsh_autosuggest_prev_cmd)
+		prev_cmd="$(_zsh_autosuggest_escape_command_prefix $prev_cmd)"
+
+		# Iterate up to the first 200 history event numbers that match $prefix
+		for key in "${(@)history_match_keys[1,200]}"; do
+			# Stop if we ran out of history
+			[[ $key -gt 1 ]] || break
+
+			# See if the history entry preceding the suggestion matches the
+			# previous command, and use it if it does
+			if [[ "${history[$((key - 1))]}" == $prev_cmd ]]; then
+				history_key=$key
+				break
+			fi
+		done
+	fi
+
+	# Echo the matched history entry
+	echo -E "$history[$history_key]"
 }
 
 _zsh_autosuggest_escape_command_prefix() {

zsh-autosuggestions.zsh

@@ -34,6 +34,18 @@
 # More info: http://zsh.sourceforge.net/Doc/Release/Zsh-Line-Editor.html#Zle-Widgets
 ZSH_AUTOSUGGEST_HIGHLIGHT_STYLE='fg=8'
 
+# Set this to enable matching the history entry preceding the suggestion
+# against the previously executed command.
+# For example, if your have just executed:
+#   pwd
+#   ls foo
+#   ls bar
+#   pwd
+# And then you start typing 'ls', then the suggestion will be 'ls foo',
+# rather than 'ls bar', as your most recently executed command (pwd)
+# was succeeded by 'ls foo' on it's previous invocation.
+unset ZSH_AUTOSUGGEST_MATCH_PREV_CMD
+
 # Prefix to use when saving original versions of bound widgets
 ZSH_AUTOSUGGEST_ORIGINAL_WIDGET_PREFIX=autosuggest-orig-
 
@@ -289,16 +301,44 @@ zle -N autosuggest-clear _zsh_autosuggest_widget_clear
 # Suggestion                                                         #
 #--------------------------------------------------------------------#
 
+# Get the peviously executed command (hookable for testing)
+_zsh_autosuggest_prev_cmd() {
+	echo -E "${history[$((HISTCMD-1))]}"
+}
+
 # Get a suggestion from history that matches a given prefix
 _zsh_autosuggest_suggestion() {
 	local prefix="$(_zsh_autosuggest_escape_command_prefix "$1")"
 
-	# Get all history items (reversed) that match pattern $prefix*
+	# Get all history event numbers (reversed) that correspond to history
-	local history_matches
+	# entries that match pattern $prefix*
-	history_matches=(${(j:\0:s:\0:)history[(R)$prefix*]})
+	local history_match_keys=(${(k)history[(R)$prefix*]})
 
-	# Echo the first item that matches
+	# By default we use the first history number (most recent history entry)
-	echo -E "$history_matches[1]"
+	local history_key="$history_match_keys[1]"
+
+	# If matching on the previous command is enabled ...
+	if (( ${+ZSH_AUTOSUGGEST_MATCH_PREV_CMD} )); then
+		# Get the previously executed command
+		local prev_cmd=$(_zsh_autosuggest_prev_cmd)
+		prev_cmd="$(_zsh_autosuggest_escape_command_prefix $prev_cmd)"
+
+		# Iterate up to the first 200 history event numbers that match $prefix
+		for key in "${(@)history_match_keys[1,200]}"; do
+			# Stop if we ran out of history
+			[[ $key -gt 1 ]] || break
+
+			# See if the history entry preceding the suggestion matches the
+			# previous command, and use it if it does
+			if [[ "${history[$((key - 1))]}" == $prev_cmd ]]; then
+				history_key=$key
+				break
+			fi
+		done
+	fi
+
+	# Echo the matched history entry
+	echo -E "$history[$history_key]"
 }
 
 _zsh_autosuggest_escape_command_prefix() {