Parse quotes when extracting words from command history (#291)

This avoids splitting on quoted whitespace when extracting words
from the command history using the emacs M-. or vi _ command.

Example: if the prior command is

$ ls Stairway\ To\ Heaven.mp3

then, M-. in Emacs editing mode (and _ in vi mode) now inserts
Stairway\ To\ Heaven.mp3 instead of Heaven.mp3. The behavior is
similar for 'Stairway To Heaven.mp3' and "Stairway To Heaven.mp3".

src/cmd/ksh93/edit/history.c: hist_word():
- Skip over single-quoted and double-quoted strings and
  backslash-escaped characters.

src/cmd/ksh93/tests/pty.sh:
- Add regression test for this feature in vi mode. Since emacs and
  vi both use the same code for this, that should be good enough.

Co-authored-by: Martijn Dekker <martijn@inlv.org>

NEWS

@@ -5,6 +5,11 @@ Any uppercase BUG_* names are modernish shell bug IDs.
 
 2021-04-30:
 
+- The emacs 'ESC .' (M-.) and vi '_' commands now take shell quoting into
+  account when repeating a word from the previous command line. For example, if
+  the previous command is 'ls Stairway\ To\ Heaven.mp3', then they now insert
+  'Stairway\ To\ Heaven.mp3' instead of 'Heaven.mp3'. Thanks to Govind Kamat.
+
 - Fixed a bug introduced on 2020-09-05 that caused "echo ${var:+'{}'}"
   to be misparsed.
 

src/cmd/ksh93/edit/history.c

@@ -1057,6 +1057,8 @@ int hist_copy(char *s1,int size,int command,int line)
 char *hist_word(char *string,int size,int word)
 {
 	register int c;
+	register int is_space;
+	register int quoted;
 	register char *s1 = string;
 	register unsigned char *cp = (unsigned char*)s1;
 	register int flag = 0;
@@ -1064,21 +1066,32 @@ char *hist_word(char *string,int size,int word)
 	if(!hp)
 		return(NIL(char*));
 	hist_copy(string,size,(int)hp->histind-1,-1);
-	for(;c = *cp;cp++)
+	for(quoted=0;c = *cp;cp++)
 	{
-		c = isspace(c);
+		is_space = isspace(c) && !quoted;
-		if(c && flag)
+		if(is_space && flag)
 		{
 			*cp = 0;
 			if(--word==0)
 				break;
 			flag = 0;
 		}
-		else if(c==0 && flag==0)
+		else if(is_space==0 && flag==0)
 		{
 			s1 = (char*)cp;
 			flag++;
 		}
+		if (c=='\'' && !quoted)
+		{
+			for(cp++;*cp && *cp != c;cp++)
+				;
+		}
+		else if (c=='\"' && !quoted)
+		{
+			for(cp++;*cp && (*cp != c || quoted);cp++)
+				quoted = *cp=='\\' ? !quoted : 0;
+		}
+		quoted = *cp=='\\' ? !quoted : 0;
 	}
 	*cp = 0;
 	if(s1 != string)

src/cmd/ksh93/tests/pty.sh

@@ -812,5 +812,19 @@ r ^:test-1: echo ok\r\n$
 r ^ok\r\n$
 !
 
+# err_exit #
+((SHOPT_VSH)) && tst $LINENO <<"!"
+L split on quoted whitespace when extracting words from command history
+# https://github.com/ksh93/ksh/pull/291
+
+d 15
+p :test-1:
+w true ls One\\ "Two Three"$'Four Five'.mp3
+r ^:test-1: true ls One\\ "Two Three"\$'Four Five'\.mp3\r\n$
+p :test-2:
+w :\E_
+r ^:test-2: : One\\ "Two Three"\$'Four Five'\.mp3\r\n$
+!
+
 # ======
 exit $((Errors<125?Errors:125))