Fix multiple bugs in emacs and vi (#565)

This (somewhat expanded) commit addresses three behaviors in vi
mode and two behaviors in emacs mode:

- In vi mode, calling v from a completely empty line rings the bell
  rather than calling the full editor.
- In vi mode, calling v from a spaces-only line results in an
  "invalid range" hist error, and the editor fails to open.
- In emacs mode, calling the full editor saves the current contents
  of the command line to the history file without a new line.
  (issue #563)
- In both editing modes, navigating to a null or empty history line
  displays an empty line onscreen.

A summary of the fixes:

The hist builtin seems to expect either a new line with the cursor
in position 0 or a line with at least one non-space character; in
all cases, the line should conclude with \n and \0:

- In vi.c, set the position to 0, refresh and insert \n if command
  mode v is called from an empty line or a line made up entirely of
  spaces. This enables hist to call the full editor with an
  appropriate range.
- In emacs.c, add \n and \0 to drawbuff before calling ed_fulledit
  (but after checking its failure conditions). This prevents the
  insertion of null history items for both empty and non-empty
  lines. Because lines composed entirely of spaces can cause the
  following prompt to be offset, clear such lines as well.

Other shells, including mksh, oksh, bash and yash, also save empty
history lines. However, actually displaying these blank lines when
navigating using e.g. the arrow keys (as is the case in ksh, mksh
and oksh) is unhelpful:

- In vi.c and emacs.c, check the history line for non-space
  characters. If the line is completely empty, resend the
  appropriate key provided that doing so would not go beyond the
  confines of the first and last history lines. This effectively
  skips empty lines when navigating.

Another bugfix:

Attempting to tab-complete an alias or $PATH item containing wide
characters before the first normal-width character has been entered
fails in both vi and emacs modes (see #532). The mechanism for
finding empty lines does not recognize wide non-space characters as
non-space characters, so lines with nothing but wide characters
always fail to reach the completion stage. When SHOPT_MULTIBYTE,
use !iswspace rather than !isspace to detect wide characters.
(bug introduced by a874586)

Resolves: #532
Resolves: #563

NEWS

@@ -2,6 +2,24 @@ This documents significant changes in the dev branch of ksh 93u+m.
 For full details, see the git log at: https://github.com/ksh93/ksh
 Uppercase BUG_* IDs are shell bug IDs as used by the Modernish shell library.
 
+2022-10-31:
+
+- In vi mode, issuing the v command from a completely empty line now invokes
+  the full editor with an empty file instead of beeping.
+
+- Fixed a bug in vi mode where the v command from a line with only whitespace
+  resulted in an "invalid range" hist error and the editor failed to open.
+
+- Fixed a bug in emacs mode where calling the full editor saved the current
+  command line to the history file without a terminating newline.
+
+- Fixed a bug in emacs and vi modes where navigating to a null or empty
+  history line displays an empty line onscreen.
+
+- Fixed a bug in emacs and vi modes where attempting to tab-complete an
+  alias or $PATH item containing wide characters failed before the first
+  normal-width character had been entered.
+
 2022-10-28:
 
 - [1.1 change] For security reasons, type attributes of variables are no longer

src/cmd/ksh93/edit/emacs.c

@@ -71,6 +71,9 @@ One line screen editor for any program
 #include	"history.h"
 #include	"edit.h"
 #include	"terminal.h"
+#if SHOPT_MULTIBYTE
+#include	<wctype.h>
+#endif /* SHOPT_MULTIBYTE */
 
 #define ESH_NFIRST
 #define ESH_KAPPEND
@@ -175,12 +178,14 @@ 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 allwhitespace(Emacs_t*, genchar*);
 
 int ed_emacsread(void *context, int fd,char *buff,int scend, int reedit)
 {
 	Edit_t *ed = (Edit_t*)context;
 	register int c;
 	register int i;
+	register int uparrow;
 	register genchar *out;
 	register int count;
 	register Emacs_t *ep = ed->e_emacs;
@@ -645,6 +650,7 @@ int ed_emacsread(void *context, int fd,char *buff,int scend, int reedit)
 				continue;
 #endif
 			}
+			uparrow = 1;
 			goto common;
 
 		case cntl('O') :
@@ -671,6 +677,7 @@ int ed_emacsread(void *context, int fd,char *buff,int scend, int reedit)
 			}
 			hline = location.hist_command;
 			hloff = location.hist_line;
+			uparrow = 0;
 		common:
 #ifdef ESH_NFIRST
 			location.hist_command = hline;	/* save current position */
@@ -686,6 +693,13 @@ int ed_emacsread(void *context, int fd,char *buff,int scend, int reedit)
 			eol = genlen(out);
 			cur = eol;
 			draw(ep,UPDATE);
+			if(allwhitespace(ep,out))
+			{
+				if(!uparrow && hline != histlines)
+					ed_ungetchar(ep->ed,cntl('N'));
+				if(uparrow && hline != hismin)
+					ed_ungetchar(ep->ed,cntl('P'));
+			}
 			continue;
 		}
 	}
@@ -951,18 +965,7 @@ static int escape(register Emacs_t* ep,register genchar *out,int count)
 		case '*':		/* filename expansion */
 		case '=':	/* escape = - list all matching file names */
 		{
-			char allempty = 1;
-			int x;
-			ep->mark = cur;
-			for(x=0; x < cur; x++)
-			{
-				if(!isspace(out[x]))
-				{
-					allempty = 0;
-					break;
-				}
-			}
-			if(cur<1 || allempty)
+			if(cur<1 || allwhitespace(ep,out))
 			{
 				beep();
 				return(-1);
@@ -1233,6 +1236,21 @@ static void xcommands(register Emacs_t *ep,int count)
 
 #ifdef ESH_BETTER
                 case cntl('E'):	/* invoke emacs on current command */
+			if(eol>=0 && sh.hist_ptr)
+			{
+				if(allwhitespace(ep,drawbuff))
+				{
+					cur = 0;
+					eol = 1;
+					drawbuff[cur] = '\n';
+					drawbuff[eol] = '\0';
+				}
+				else
+				{
+					drawbuff[eol] = '\n';
+					drawbuff[eol+1] = '\0';
+				}
+			}
 			if(ed_fulledit(ep->ed)==-1)
 				beep();
 			else
@@ -1688,4 +1706,19 @@ static int _isword(register int c)
 }
 #endif /* SHOPT_MULTIBYTE */
 
+static char allwhitespace(register Emacs_t *ep, register genchar *out)
+{
+	int x;
+	ep->mark = cur;
+	for(x=0; x < cur; x++)
+	{
+#if SHOPT_MULTIBYTE
+		if(!iswspace((wchar_t)out[x]))
+#else
+		if(!isspace(out[x]))
+#endif /* SHOPT_MULTIBYTE */
+			return(0);
+	}
+	return(1);
+}
 #endif /* SHOPT_ESH */

src/cmd/ksh93/edit/vi.c

@@ -52,6 +52,7 @@
 
 #if SHOPT_MULTIBYTE
 #   include	"lexstates.h"
+#   include	<wctype.h>
 #   define gencpy(a,b)	ed_gencpy(a,b)
 #   define genncpy(a,b,n)	ed_genncpy(a,b,n)
 #   define genlen(str)	ed_genlen(str)
@@ -174,6 +175,7 @@ typedef struct _vi_
 
 static const char paren_chars[] = "([{)]}";   /* for % command */
 
+static char	allwhitespace(Vi_t*);
 static void	cursor(Vi_t*, int);
 static void	del_line(Vi_t*,int);
 static int	getcount(Vi_t*,int);
@@ -704,6 +706,7 @@ static int cntlmode(Vi_t *vp)
 {
 	register int c;
 	register int i;
+	register int uparrow;
 	genchar tmp_u_space[MAXLINE];	/* temporary u_space */
 	genchar *real_u_space;		/* points to real u_space */
 	int tmp_u_column = INVALID;	/* temporary u_column */
@@ -859,6 +862,7 @@ static int cntlmode(Vi_t *vp)
 			}
 			save_v(vp);
 			cur_virt = INVALID;
+			uparrow = 0;
 			goto newhist;
 
 		case 'k':		/** get previous command **/
@@ -881,6 +885,7 @@ static int cntlmode(Vi_t *vp)
 			}
 			save_v(vp);
 			cur_virt = INVALID;
+			uparrow = 1;
 		newhist:
 			if(curhline!=histmax || cur_virt==INVALID)
 				hist_copy((char*)virtual, MAXLINE, curhline,-1);
@@ -896,6 +901,13 @@ static int cntlmode(Vi_t *vp)
 #endif /* SHOPT_MULTIBYTE */
 			if((last_virt=genlen(virtual)-1) >= 0  && cur_virt == INVALID)
 				cur_virt = 0;
+			if(allwhitespace(vp))
+			{
+				if(uparrow && curhline != histmin)
+					ed_ungetchar(vp->ed,'k');
+				if(!uparrow && curhline != histmax)
+					ed_ungetchar(vp->ed,'j');
+			}
 			break;
 
 
@@ -917,7 +929,16 @@ static int cntlmode(Vi_t *vp)
 
 		case 'v':
 			if(vp->repeat_set==0)
+			{
+				if(allwhitespace(vp) || cur_virt == INVALID)
+				{
+					cur_virt = 0;
+					last_virt = cur_virt;
+					refresh(vp,TRANSLATE);
+					virtual[last_virt++] = '\n';
+				}
 				goto vcommand;
+			}
 			/* FALLTHROUGH */
 
 		case 'G':		/** goto command repeat **/
@@ -1485,17 +1506,7 @@ static void getline(register Vi_t* vp,register int mode)
 
 		case '\t':		/** command completion **/
 		{
-			char allempty = 1;
-			int x;
-			for(x=0; x <= cur_virt; x++)
-			{
-				if(!isspace(virtual[x]))
-				{
-					allempty = 0;
-					break;
-				}
-			}
-			if(allempty)
+			if(allwhitespace(vp))
 			{
 				ed_ringbell();
 				break;
@@ -2533,17 +2544,7 @@ static int textmod(register Vi_t *vp,register int c, int mode)
 	case '\\':		/** do file name completion in place **/
 	case '=':		/** list file name expansions **/
 	{
-		char allempty = 1;
-		int x;
-		for(x=0; x <= cur_virt; x++)
-		{
-			if(!isspace(virtual[x]))
-			{
-				allempty = 0;
-				break;
-			}
-		}
-		if(cur_virt == INVALID || allempty)
+		if(cur_virt == INVALID || allwhitespace(vp))
 			return(BAD);
 		/* FALLTHROUGH */
 		save_v(vp);
@@ -2884,6 +2885,24 @@ static int textmod(register Vi_t *vp,register int c, int mode)
     }
 #endif	/* SHOPT_MULTIBYTE */
 
+/*
+ * determine if a line is entirely blank
+ */
+static char allwhitespace(register Vi_t *vp)
+{
+	int x;
+	for(x=0; x <= cur_virt; x++)
+	{
+#if SHOPT_MULTIBYTE
+		if(!iswspace((wchar_t)virtual[x]))
+#else
+		if(!isspace(virtual[x]))
+#endif /* SHOPT_MULTIBYTE */
+			return(0);
+	}
+	return(1);
+}
+
 /*
  * get a character, after ^V processing
  */