vi: Fix recalling lines starting with whitespace (re: 161139d)

@jghub reports:
> if for some reason a command is entered with leading whitespace,
> the leading whitespace is preserved in the history file (in
> ksh93u+, too). such commands can be recalled from history in 93u+
> without problem, both, in vi and emacs mode.
>
> but in 93u+m such entries are simply ignored when using vi-mode
> (set -o vi), i.e. the k and j commands skip over such entries.
> emacs mode still works just fine.

Analysis: the blankline() function in vi.c and emacs.c is used to
check for whitespace up to the cursor position. This is used for
tab completion and fullscreen editor invocation, where that is
okay, and for history recall, where that should be checking the
entire line instead.

In emacs.c this was not really a problem because arrowing up (or
^P) positions the cursor to the end of the line anyway. But in vi,
arrowing up (or 'k') positions the cursor at the beginning.

src/cmd/ksh93/edit/vi.c:
- Amend blankline() with an 'uptocursor' argument. If nonzero, it
  checks the current line for whitespace up to the cursor position,
  otherwise it checks the entire line.
- Pass uptocursor==0 to blankline() for history recall and 1 for
  tab completion.

src/cmd/ksh93/edit/emacs.c:
- Apply the same change here for consistency, even though it's
  perhaps not really necessary. If ever a form of recall is added
  that doesn't position the cursor at the end, then that won't
  introduce this bug there.

Thanks to @pghvlaans for input into the fix.
Resolves: #799

NEWS

@@ -2,6 +2,12 @@ This documents significant changes in the 1.0 branch of ksh 93u+m.
 For full details, see the git log at: https://github.com/ksh93/ksh/tree/1.0
 Uppercase BUG_* IDs are shell bug IDs as used by the Modernish shell library.
 
+2024-12-05:
+
+- Fixed an issue in the vi line editors where lines beginning with whitespace
+  could not be recalled from the history (e.g. with arrow up). Bug introduced
+  on 2022-10-31.
+
 2024-11-26:
 
 - The -v/--verbose option of the cp, mv and ln built-in commands (which are

src/cmd/ksh93/edit/emacs.c

@@ -174,7 +174,7 @@ static void search(Emacs_t*,genchar*,int);
 static void setcursor(Emacs_t*,int, int);
 static void show_info(Emacs_t*,const char*);
 static void xcommands(Emacs_t*,int);
-static char blankline(Emacs_t*, genchar*);
+static int blankline(Emacs_t*, genchar*, int);
 
 int ed_emacsread(void *context, int fd,char *buff,int scend, int reedit)
 {
@@ -716,9 +716,9 @@ int ed_emacsread(void *context, int fd,char *buff,int scend, int reedit)
 			cur = eol;
 			draw(ep,UPDATE);
 			/* skip blank lines when going up/down in history */
-			if(c==cntl('N') && hline != histlines && blankline(ep,out))
+			if(c==cntl('N') && hline != histlines && blankline(ep,out,0))
 				ed_ungetchar(ep->ed,cntl('N'));
-			else if(c==cntl('P') && hline != hismin && blankline(ep,out))
+			else if(c==cntl('P') && hline != hismin && blankline(ep,out,0))
 				ed_ungetchar(ep->ed,cntl('P'));
 			continue;
 		}
@@ -1007,7 +1007,7 @@ static int escape(Emacs_t* ep,genchar *out,int count)
 		case '*':		/* filename expansion */
 		case '=':	/* escape = - list all matching file names */
 		{
-			if(cur<1 || blankline(ep,out))
+			if(cur<1 || blankline(ep,out,1))
 			{
 				beep();
 				return -1;
@@ -1296,7 +1296,7 @@ static void xcommands(Emacs_t *ep,int count)
 		case cntl('E'):	/* invoke emacs on current command */
 			if(eol>=0 && sh.hist_ptr)
 			{
-				if(blankline(ep,drawbuff))
+				if(blankline(ep,drawbuff,1))
 				{
 					cur = 0;
 					eol = 1;
@@ -1769,11 +1769,11 @@ static int _isword(int c)
 /*
  * determine if the command line is blank (empty or all whitespace)
  */
-static char blankline(Emacs_t *ep, genchar *out)
+static int blankline(Emacs_t *ep, genchar *out, int uptocursor)
 {
 	int x;
 	ep->mark = cur;
-	for(x=0; x < cur; x++)
+	for(x=0; uptocursor ? (x < cur) : (x <= eol); x++)
 	{
 #if SHOPT_MULTIBYTE
 		if(!iswspace((wchar_t)out[x]))

src/cmd/ksh93/edit/vi.c

@@ -174,7 +174,7 @@ typedef struct _vi_
 
 static const char paren_chars[] = "([{)]}";   /* for % command */
 
-static char	blankline(Vi_t*);
+static int	blankline(Vi_t*, int);
 static void	cursor(Vi_t*, int);
 static void	del_line(Vi_t*,int);
 static int	getcount(Vi_t*,int);
@@ -668,9 +668,9 @@ static int cntlmode(Vi_t *vp)
 			}
 #endif /* SHOPT_EDPREDICT */
 			/* skip blank lines when going up/down in history */
-			if((c=='k' || c=='-') && curhline != histmin && blankline(vp))
+			if((c=='k' || c=='-') && curhline != histmin && blankline(vp,0))
 				ed_ungetchar(vp->ed,'k');
-			else if((c=='j' || c=='+') && curhline != histmax && blankline(vp))
+			else if((c=='j' || c=='+') && curhline != histmax && blankline(vp,0))
 				ed_ungetchar(vp->ed,'j');
 			break;
 
@@ -694,7 +694,7 @@ static int cntlmode(Vi_t *vp)
 		case 'v':
 			if(vp->repeat_set==0)
 			{
-				if(blankline(vp) || cur_virt == INVALID)
+				if(blankline(vp,1) || cur_virt == INVALID)
 				{
 					cur_virt = 0;
 					last_virt = cur_virt;
@@ -1297,7 +1297,7 @@ static void getline(Vi_t* vp,int mode)
 		{
 			if(!sh_isoption(SH_VI) || !sh.nextprompt)
 				goto fallback;
-			if(blankline(vp))
+			if(blankline(vp,1))
 			{
 				ed_ringbell();
 				break;
@@ -2289,7 +2289,7 @@ static int textmod(Vi_t *vp,int c, int mode)
 	case '\\':		/** do file name completion in place **/
 	case '=':		/** list file name expansions **/
 	{
-		if(cur_virt == INVALID || blankline(vp))
+		if(cur_virt == INVALID || blankline(vp,1))
 			return BAD;
 		/* FALLTHROUGH */
 		save_v(vp);
@@ -2645,10 +2645,10 @@ static int textmod(Vi_t *vp,int c, int mode)
 /*
  * determine if the command line is blank (empty or all whitespace)
  */
-static char blankline(Vi_t *vp)
+static int blankline(Vi_t *vp, int uptocursor)
 {
 	int x;
-	for(x=0; x <= cur_virt; x++)
+	for(x=0; x <= (uptocursor ? cur_virt : last_virt); x++)
 	{
 #if SHOPT_MULTIBYTE
 		if(!iswspace((wchar_t)virtual[x]))

src/cmd/ksh93/include/version.h

@@ -18,7 +18,7 @@
 #include <ast_release.h>
 #include "git.h"
 
-#define SH_RELEASE_DATE	"2024-12-03"	/* must be in this format for $((.sh.version)) */
+#define SH_RELEASE_DATE	"2024-12-05"	/* must be in this format for $((.sh.version)) */
 /*
  * This comment keeps SH_RELEASE_DATE a few lines away from SH_RELEASE_SVER to avoid
  * merge conflicts when cherry-picking dev branch commits onto a release branch.

src/cmd/ksh93/tests/pty.sh

@@ -1337,5 +1337,17 @@ w print Exit status $?
 u ^Exit status 0\r\n$
 !
 
+((SHOPT_VSH)) && tst $LINENO <<"!"
+L 'k' skips over history entries starting with whitespace
+# https://github.com/ksh93/ksh/issues/799
+
+d 40
+p :test-1:
+w   true
+p :test-2:
+c \Ek
+r :test-2:   true
+!
+
 # ======
 exit $((Errors<125?Errors:125))