Re: parsing empty alternatives: case foo|) :;;

[Peter Stephenson <p.w.stephenson@ntlworld.com>]

On Mon, 07 Aug 2017 15:58:56 +0100
Peter Stephenson <p.stephenson@samsung.com> wrote:
> I think this might be some fix-up code that got added for the old case
> (nothing to do with pipes in that case).

It's complicated because of the two cases, but I'm not sure this ever
worked.

It's straightforward to fix, but note I can't fix "foo||bar)" without
more work because || is a different token.  I think we can probably
avoid parsing it that way here if we want to go down that route.

I deliberately haven't tried to squeeze this into 5.4.

pws

diff --git a/Src/parse.c b/Src/parse.c
index ba9cd61..d99826d 100644
--- a/Src/parse.c
+++ b/Src/parse.c
@@ -1194,6 +1194,7 @@ par_case(int *cmplx)
 
     for (;;) {
 	char *str;
+	int skip_zshlex;
 
 	while (tok == SEPER)
 	    zshlex();
@@ -1201,11 +1202,17 @@ par_case(int *cmplx)
 	    break;
 	if (tok == INPAR)
 	    zshlex();
-	if (tok != STRING)
-	    YYERRORV(oecused);
-	if (!strcmp(tokstr, "esac"))
-	    break;
-	str = dupstring(tokstr);
+	if (tok == BAR) {
+	    str = dupstring("");
+	    skip_zshlex = 1;
+	} else {
+	    if (tok != STRING)
+		YYERRORV(oecused);
+	    if (!strcmp(tokstr, "esac"))
+		break;
+	    str = dupstring(tokstr);
+	    skip_zshlex = 0;
+	}
 	type = WC_CASE_OR;
 	pp = ecadd(0);
 	palts = ecadd(0);
@@ -1245,8 +1252,9 @@ par_case(int *cmplx)
 	 */
 	incasepat = 0;
 	incmdpos = 1;
-	for (;;) {
+	if (!skip_zshlex)
 	    zshlex();
+	for (;;) {
 	    if (tok == OUTPAR) {
 		ecstr(str);
 		ecadd(ecnpats++);
@@ -1302,9 +1310,24 @@ par_case(int *cmplx)
 	    }
 
 	    zshlex();
-	    if (tok != STRING)
+	    switch (tok) {
+	    case STRING:
+		/* Normal case */
+		str = dupstring(tokstr);
+		zshlex();
+		break;
+
+	    case OUTPAR:
+	    case BAR:
+		/* Empty string */
+		str = dupstring("");
+		break;
+
+	    default:
+		/* Oops. */
 		YYERRORV(oecused);
-	    str = dupstring(tokstr);
+		break;
+	    }
 	}
 	par_save_list(cmplx);
 	if (tok == SEMIAMP)
diff --git a/Test/A01grammar.ztst b/Test/A01grammar.ztst
index 9625a15..db62875 100644
--- a/Test/A01grammar.ztst
+++ b/Test/A01grammar.ztst
@@ -820,6 +820,26 @@
 0:case keeps exit status of last command executed in compound-list
 >37
 
+  case '' in
+    burble) print No.
+    ;;
+    spurble|) print Yes!
+    ;;
+    |burble) print Not quite.
+    ;;
+  esac
+  case '' in
+    burble) print No.
+    ;;
+    |burble) print Wow!
+    ;;
+    spurble|) print Sorry.
+    ;;
+  esac
+0: case with no opening parentheses and empty string 
+>Yes!
+>Wow!
+
   x=1
   x=2 | echo $x
   echo $x