Fix multiple bugs when using 'alias -p' to print aliases (#398)

This commit was originally intended to fix just one bug with shcomp's
handling of 'alias -p', but while fixing that I found a large number
of related issues in the alias command's -p, -t and -x options. The
current patch provides bugfixes for all of the bugs listed below:

1) Listing aliases in a script with 'alias -p' or 'alias' broke
   shcomp's bytecode output:
   https://github.com/ksh93/ksh/issues/87#issuecomment-813819122

2) Listing individual aliases with the -p option doesn't work:
      $ alias foo=bar bar=foo
      $ alias foo
      foo=bar
      $ alias -p foo  # No output

3) Listing specific tracked aliases with -pt does not display them
   in a reusable format, but rather adds another tracked alias:
      $ hash -r cat vi
      $ alias -pt vi  # No output
      $ alias -pt rm
      $ alias -t
      cat=/usr/bin/cat
      rm=/usr/bin/rm
      vi=/usr/bin/vi

4) Listing all tracked aliases with -pt does not output them in a
   reusable format (the resulting command printed only creates a
   normal alias, which is different from a tracked alias):
      $ hash -r cat
      $ alias -pt
      alias cat=/usr/bin/cat  # Expected 'alias -t cat'

5) Listing a non-existent alias with -p doesn't cause an error:
      $ unalias -a
      $ alias -p notanalias  # No output
      $ echo $?
      0
      $ alias notanalias
      notanalias: alias not found
      $ echo $?
      1
      $ hash -r
      $ alias -pt notacommand  # No output
      $ echo $?
      0

6) Attempting to list 256 non-existent aliases results in exit
   status zero:
      $ unalias -a
      $ alias $(awk -v ORS= 'BEGIN { for(i=0;i<256;i++) print "x "; }')
      x: alias not found
      --cut error message--
      $ echo $?
      0

Changes:

- typeset.c: Avoid printing anything while shcomp is compiling a
  script. This is needed because the alias command is run by shcomp
  to prevent parsing issues.

- b_alias(): To avoid adding tracked aliases with -pt, set
  tdata.aflag to '+' so that setall() and other related functions
  only list tracked aliases.

- b_alias(): Set tdata.pflag to 1 so that setall() and other
  functions recognize -p was passed.

- print_value(): Add support for listing specific aliases with
  'alias -p'.

- setall(): To avoid any issues with zombie tracked aliases (see also
  the regression tests) ignore tracked alias nodes marked with the
  NV_NOALIAS attribute. This bit is set for tracked alias nodes by
  the nv_rehash() function.

- setall(): For backward compatibility, continue incrementing the
  exit status for each invalid alias and tracked alias passed. This
  was already how alias behaved when listing aliases without -p, so
  using -p shouldn't cause a change in behavior:
      $ unalias -a
      $ alias foo bar
      foo: alias not found
      bar: alias not found
      $ echo $?
      2
  To fix bug 6, the exit status is set to one if an enforced 8-bit
  exit status would be zero.

- print_namval(): Set the prefix to 'alias -t' so that listing
  tracked aliases with 'alias -pt' works correctly.

- data/msg.c and include/name.h: Add an error message for when
  'alias -pt' doesn't find a tracked alias.

- tests/alias.sh: Add a ton of regression tests for the bugs fixed in
  this commit.

src/cmd/ksh93/bltins/typeset.c

@@ -132,7 +132,7 @@ int    b_alias(int argc,register char *argv[],Shbltin_t *context)
 {
 	register unsigned flag = NV_NOARRAY|NV_NOSCOPE|NV_ASSIGN;
 	register Dt_t *troot;
-	register int rflag=0, n;
+	register int rflag=0, xflag=0, n;
 	struct tdata tdata;
 	NOT_USED(argc);
 	memset((void*)&tdata,0,sizeof(tdata));
@@ -151,20 +151,26 @@ int    b_alias(int argc,register char *argv[],Shbltin_t *context)
 		{
 		    case 'p':
 			tdata.prefix = argv[0];
+			tdata.pflag = 1;
 			break;
 		    case 't':
 			flag |= NV_TAGGED;
 			break;
 		    case 'x':
 			/* obsolete, ignored */
+			xflag = 1;
 			break;
 		    case 'r':
 			rflag=1;
 			break;
 		    case ':':
+			if(sh.shcomp)
+				return(2);  /* don't print usage info while shcomp is compiling */
 			errormsg(SH_DICT,2, "%s", opt_info.arg);
 			break;
 		    case '?':
+			if(sh.shcomp)
+				return(2);
 			errormsg(SH_DICT,ERROR_usage(0), "%s", opt_info.arg);
 			return(2);
 		}
@@ -179,12 +185,17 @@ int    b_alias(int argc,register char *argv[],Shbltin_t *context)
 	if(flag&NV_TAGGED)
 	{
 		troot = sh_subtracktree(1);	/* use hash table */
-		tdata.aflag = '-';		/* make setall() treat 'hash' like 'alias -t' */
+		if(tdata.pflag)
+			tdata.aflag = '+';	/* for 'alias -pt', don't add anything to the hash table */
+		else
+			tdata.aflag = '-';	/* make setall() treat 'hash' like 'alias -t' */
 		if(rflag)			/* hash -r: clear hash table */
 			nv_scan(troot,nv_rehash,(void*)0,NV_TAGGED,NV_TAGGED);
 	}
 	else if(argv[1] && tdata.sh->subshell && !tdata.sh->subshare)
 		sh_subfork();			/* avoid affecting the parent shell's alias table */
+	if(xflag && (flag&NV_TAGGED))
+		return(0);			/* do nothing for 'alias -tx' */
 	return(setall(argv,flag,troot,&tdata));
 }
 
@@ -597,6 +608,8 @@ static void print_value(Sfio_t *iop, Namval_t *np, struct tdata *tp)
 		sfwrite(iop,"}\n",2);
 		return;
 	}
+	if(tp->prefix && *tp->prefix=='a' && !nv_isattr(np,NV_TAGGED))
+		sfprintf(iop,"%s ", tp->prefix);
 	table = tp->sh->last_table;
 	sfputr(iop,nv_name(np),aflag=='+'?'\n':'=');
 	tp->sh->last_table = table;
@@ -736,8 +749,16 @@ static int     setall(char **argv,register int flag,Dt_t *troot,struct tdata *tp
 				continue;
 			}
 			np = nv_open(name,troot,nvflags|((nvflags&NV_ASSIGN)?0:NV_ARRAY)|((iarray|(nvflags&(NV_REF|NV_NOADD)==NV_REF))?NV_FARRAY:0));
-			if(!np)
+			if(!np || (troot==sh.track_tree && nv_isattr(np,NV_NOALIAS)))
+			{
+				if(troot==sh.alias_tree || troot==sh.track_tree)
+				{
+					if(!sh.shcomp)
+						sfprintf(sfstderr,sh_translate(troot==sh.alias_tree ? e_noalias: e_notrackedalias),name);
+					r++;
+				}
 				continue;
+			}
 			if(np->nvflag&NV_RDONLY && !tp->pflag
 			&& (flag & ~(NV_ASSIGN|NV_RDONLY|NV_EXPORT)))	/* allow readonly/export on readonly vars */
 			{
@@ -775,7 +796,8 @@ static int     setall(char **argv,register int flag,Dt_t *troot,struct tdata *tp
 			{
 				if(troot!=shp->var_tree && (nv_isnull(np) || !print_namval(sfstdout,np,0,tp)))
 				{
-					sfprintf(sfstderr,sh_translate(e_noalias),name);
+					if(!sh.shcomp)
+						sfprintf(sfstderr,sh_translate(e_noalias),name);
 					r++;
 				}
 				if(!comvar && !iarray)
@@ -979,6 +1001,14 @@ static int     setall(char **argv,register int flag,Dt_t *troot,struct tdata *tp
 			print_all(sfstdout,troot,tp);
 		sfsync(sfstdout);
 	}
+	/* This is to handle cases where more than 255 non-existent
+	   aliases were passed to the alias command. */
+	if(r>255)
+	{
+		r &= SH_EXITMASK;
+		if(r==0)
+			r = 1;  /* ensure the exit status is at least 1 */
+	}
 	return(r);
 }
 
@@ -1404,6 +1434,8 @@ static int print_namval(Sfio_t *file,register Namval_t *np,register int flag, st
 		flag = '\n';
 	if(tp->noref && nv_isref(np))
 		return(0);
+	if(sh.shcomp)
+		return(1);  /* print nothing while shcomp is compiling */
 	if(nv_isattr(np,NV_NOPRINT|NV_INTEGER)==NV_NOPRINT)
 	{
 		if(is_abuiltin(np))
@@ -1418,7 +1450,9 @@ static int print_namval(Sfio_t *file,register Namval_t *np,register int flag, st
 	isfun = is_afunction(np);
 	if(tp->prefix)
 	{
-		outname = (*tp->prefix=='t' &&  (!nv_isnull(np) || nv_isattr(np,NV_FLOAT|NV_RDONLY|NV_BINARY|NV_RJUST|NV_NOPRINT)));
+		outname = (*tp->prefix=='t' && (!nv_isnull(np) || nv_isattr(np,NV_FLOAT|NV_RDONLY|NV_BINARY|NV_RJUST|NV_NOPRINT)));
+		if(tp->scanroot==sh.track_tree && *tp->prefix=='a')
+			tp->prefix = "alias -t";
 		if(indent && (isfun || outname || *tp->prefix!='t'))
 		{
 			sfnputc(file,'\t',indent);
@@ -1427,7 +1461,7 @@ static int print_namval(Sfio_t *file,register Namval_t *np,register int flag, st
 		if(!isfun)
 		{
 			if(*tp->prefix=='t')
-			nv_attribute(np,tp->outfile,tp->prefix,tp->aflag);
+				nv_attribute(np,tp->outfile,tp->prefix,tp->aflag);
 			else
 				sfputr(file,tp->prefix,' ');
 		}