Aliasing part 3 (or so) - Doc and POSIX_ALIASES

[Bart Schaefer <schaefer@xxxxxxxxxxxxxxxx>]

Probably still needs a couple of tests added, and this does not address
the bugs from 34668 and 34682.

This doc is tweaked a bit from the original sample in 34715.  I looked
up aliasing in the POSIX spec and (except allowed as an extension) it
does not include glob patterns either.  This turns out to be very easy
to do along with excluding quoted strings, parameter references, etc.;
see the third hunk of the lex.c patch.  The first hunk of that patch
handles the new requirement of "alias -g" for separators et al.

After this patch the doc and the code should be consistent.  I'm still
not entirely happy about being able to alias "||", ">&", etc. for all
the reasons I've previously mentioned, but further because there's no
way to quote such a token (to prevent alias expansion) that also gives
you back a token with the same semantics.


diff --git a/Doc/Zsh/grammar.yo b/Doc/Zsh/grammar.yo
index b30e423..522ad04 100644
--- a/Doc/Zsh/grammar.yo
+++ b/Doc/Zsh/grammar.yo
@@ -538,8 +538,7 @@ If so, it is replaced by the text of the alias if it is in command
 position (if it could be the first word of a simple command),
 or if the alias is global.
 If the replacement text ends with a space, the next word in the shell input
-is treated as though it were in command position for purposes of alias
-expansion.
+is always eligible for purposes of alias expansion.
 findex(alias, use of)
 cindex(aliases, global)
 An alias is defined using the tt(alias) builtin; global aliases
@@ -555,22 +554,32 @@ itemiz(Any parameter reference or command substitution)
 itemiz(Any series of the foregoing, concatenated without whitespace or
 other tokens between them)
 itemiz(Any reserved word (tt(case), tt(do), tt(else), etc.))
+itemiz(With global aliasing, any command separator, any redirection
+operator, and `tt(LPAR())' or `tt(RPAR())' when not part of a glob pattern)
 enditemize()
 
-Reserved words are not eligible for aliasing when tt(POSIX_ALIASES) is set.
-The tt(alias) builtin does not reject ineligible aliases, but they are not
-expanded.
+It is not presently possible to alias the `tt(LPAR()LPAR())' token that
+introduces arithmetic expressions, because until a full statement has been
+parsed, it cannot be distinguished from two consecutive `tt(LPAR())'
+tokens introducing nested subshells.
+
+When tt(POSIX_ALIASES) is set, only plain unquoted strings are eligible
+for aliasing.  The tt(alias) builtin does not reject ineligible aliases,
+but they are not expanded.
 
 Alias expansion is done on the shell input before any other expansion
 except history expansion.  Therefore, if an alias is defined for the
 word tt(foo), alias expansion may be avoided by quoting part of the
 word, e.g. tt(\foo).  Any form of quoting works, although there is
 nothing to prevent an alias being defined for the quoted form such as
-tt(\foo) as well.  For use with completion, which would remove an
-initial backslash followed by a character that isn't special, it may be
-more convenient to quote the word by starting with a single quote,
-i.e. tt('foo); completion will automatically add the trailing single
-quote.
+tt(\foo) as well.  Also, if a separator such as tt(&&) is aliased,
+tt(\&&) turns into the two tokens tt(\&) and tt(&), each of which may
+have been aliased separately.  Similarly for tt(\<<), tt(\>|), etc.
+
+For use with completion, which would remove an initial backslash followed
+by a character that isn't special, it may be more convenient to quote the
+word by starting with a single quote, i.e. tt('foo); completion will
+automatically add the trailing single quote.
 
 There is a commonly encountered problem with aliases
 illustrated by the following code:
diff --git a/Src/lex.c b/Src/lex.c
index 494ea88..1eb0bc7 100644
--- a/Src/lex.c
+++ b/Src/lex.c
@@ -1740,12 +1740,13 @@ checkalias(void)
 
     if (!noaliases && isset(ALIASESOPT) &&
 	(!isset(POSIXALIASES) ||
-	 !reswdtab->getnode(reswdtab, zshlextext))) {
+	 (tok == STRING && !reswdtab->getnode(reswdtab, zshlextext)))) {
 	char *suf;
 
 	an = (Alias) aliastab->getnode(aliastab, zshlextext);
 	if (an && !an->inuse &&
-	    ((an->node.flags & ALIAS_GLOBAL) || incmdpos || inalmore)) {
+	    ((an->node.flags & ALIAS_GLOBAL) ||
+	     (incmdpos && tok == STRING) || inalmore)) {
 	    inpush(an->text, INP_ALIAS, an);
 	    if (an->text[0] == ' ' && !(an->node.flags & ALIAS_GLOBAL))
 		aliasspaceflag = 1;
@@ -1784,6 +1785,8 @@ exalias(void)
     if (!tokstr) {
 	zshlextext = tokstrings[tok];
 
+	if (tok == NEWLIN)
+	    return 0;
 	return checkalias();
     } else {
 	VARARR(char, copy, (strlen(tokstr) + 1));
@@ -1791,6 +1794,9 @@ exalias(void)
 	if (has_token(tokstr)) {
 	    char *p, *t;
 
+	    if (isset(POSIXALIASES))
+		return 0;
+
 	    zshlextext = p = copy;
 	    for (t = tokstr;
 		 (*p++ = itok(*t) ? ztokens[*t++ - Pound] : *t++););
diff --git a/Test/A02alias.ztst b/Test/A02alias.ztst
index 36dfa24..314ec03 100644
--- a/Test/A02alias.ztst
+++ b/Test/A02alias.ztst
@@ -43,7 +43,7 @@
 0:Alias expansion works at the end of parsed strings
 >foo
 
-  alias '&&=(){ return $?; } && '
+  alias -g '&&=(){ return $?; } && '
   alias not_the_print_command=print
   eval 'print This is output
   && print And so is this