Re: Surprising parsing result with anonymous functions and for loops

[Peter Stephenson <p.stephenson@xxxxxxxxxxx>]

On Thu, 25 Sep 2014 12:02:55 +0200
Mikael Magnusson <mikachu@xxxxxxxxx> wrote:
> Okay, but does anyone at least agree that doing alias expansion at
> that point is highly surprising?

You mean regardless of function behaviour?

% alias foo=bar
% for i in 1; do : ; done foo
zsh: parse error near `bar'

The parser doesn't expect anything there so doesn't make special
arrangements not to treat it as a command word because it doesn't mean
anything anyway, but this one is easy to fix.  The cases with standard
keywords are the simple ones as there must be a separator next ---
closing braces are harder because there are so many cases, but I think
loops are unproblematic (this is special to zsh).

Anything similar requires some different ad hoc change.  I had a go at
if and there are gotchas:

  if (true) { : } else { : }

is valid syntax (again this is annoying zsh-specific stuff I wish we
didn't have to maintain) so we need to be in command position after any
closing braces except after the final "else".  We've already got a
reasonable set of tests in this area for the more important non-error
case.

"while" and "repeat" look similar to "for".

The more standard uses of braces for functions are explicitly setting
incmdpos = 1 --- I can't remember why, but I've a vague memory it's
complicated.  It looks like I added a special case for anonymous
functions to set incmdpos = 0.  So you still get

% alias foo=bar
% foo() { : } foo
zsh: parse error near `bar'

and I'm not sure how much I want to look --- it would be easy to break
something here.  If we fix redirections at this point the answer may
become more obvious.

For current shell { ... } this also happens but it's a bit more
understandable as an "always" keyword can follow.

pws


diff --git a/Src/parse.c b/Src/parse.c
index 5f1303f..3633417 100644
--- a/Src/parse.c
+++ b/Src/parse.c
@@ -997,17 +997,20 @@ par_for(int *complex)
 	par_save_list(complex);
 	if (tok != DONE)
 	    YYERRORV(oecused);
+	incmdpos = 0;
 	zshlex();
     } else if (tok == INBRACE) {
 	zshlex();
 	par_save_list(complex);
 	if (tok != OUTBRACE)
 	    YYERRORV(oecused);
+	incmdpos = 0;
 	zshlex();
     } else if (csh || isset(CSHJUNKIELOOPS)) {
 	par_save_list(complex);
 	if (tok != ZEND)
 	    YYERRORV(oecused);
+	incmdpos = 0;
 	zshlex();
     } else if (unset(SHORTLOOPS)) {
 	YYERRORV(oecused);
@@ -1186,9 +1189,12 @@ par_if(int *complex)
     for (;;) {
 	xtok = tok;
 	cmdpush(xtok == IF ? CS_IF : CS_ELIF);
-	zshlex();
-	if (xtok == FI)
+	if (xtok == FI) {
+	    incmdpos = 0;
+	    zshlex();
 	    break;
+	}
+	zshlex();
 	if (xtok == ELSE)
 	    break;
 	while (tok == SEPER)
@@ -1229,6 +1235,7 @@ par_if(int *complex)
 		YYERRORV(oecused);
 	    }
 	    ecbuf[pp] = WCB_IF(type, ecused - 1 - pp);
+	    /* command word (else) allowed to follow immediately */
 	    zshlex();
 	    incmdpos = 1;
 	    if (tok == SEPER)
@@ -1266,6 +1273,7 @@ par_if(int *complex)
 		YYERRORV(oecused);
 	    }
 	}
+	incmdpos = 0;
 	ecbuf[pp] = WCB_IF(WC_IF_ELSE, ecused - 1 - pp);
 	zshlex();
 	cmdpop();
@@ -1296,12 +1304,14 @@ par_while(int *complex)
 	par_save_list(complex);
 	if (tok != DONE)
 	    YYERRORV(oecused);
+	incmdpos = 0;
 	zshlex();
     } else if (tok == INBRACE) {
 	zshlex();
 	par_save_list(complex);
 	if (tok != OUTBRACE)
 	    YYERRORV(oecused);
+	incmdpos = 0;
 	zshlex();
     } else if (isset(CSHJUNKIELOOPS)) {
 	par_save_list(complex);
@@ -1340,12 +1350,14 @@ par_repeat(int *complex)
 	par_save_list(complex);
 	if (tok != DONE)
 	    YYERRORV(oecused);
+	incmdpos = 0;
 	zshlex();
     } else if (tok == INBRACE) {
 	zshlex();
 	par_save_list(complex);
 	if (tok != OUTBRACE)
 	    YYERRORV(oecused);
+	incmdpos = 0;
 	zshlex();
     } else if (isset(CSHJUNKIELOOPS)) {
 	par_save_list(complex);