String expansions: fix ${extract }, for the numeric/3-string case. Bug 1807

Broken-by: 82dbd37

In "skipping" mode when parsing an expansion we want to avoid expanding
the arguments, as the data for expansion is not necessarily valid.  This
bit us previously for an extract within an "if inlist". But the number of
args for ${extract } depends on the expanded value of the first arg.

Retreat from strict parsing and just line up the outer braces,
accepting any number of args while skipping.  The separate
non-skipping execution will do the proper checking.

4 files changed, 45 insertions, 21 deletions

diff --git a/doc/doc-txt/ChangeLog b/doc/doc-txt/ChangeLog
index d36b731cd..320b29a53 100644
--- a/doc/doc-txt/ChangeLog
+++ b/doc/doc-txt/ChangeLog
@@ -194,6 +194,11 @@ JH/47 Fix build on HP-UX and older Solaris, which need (un)setenv now also
       for the new environment-manipulation done at startup.  Move the routines
       from being local to tls.c to being global via the os.c file.
 
+JH/48 Bug 1807: Fix ${extract } for the numeric/3-string case. While preparsing
+      an extract embedded as result-arg for a map, the first arg for extract
+      is unavailable so we cannot tell if this is a numbered or keyed
+      extraction.  Accept either.
+
 
 
 Exim version 4.86
diff --git a/src/src/expand.c b/src/src/expand.c
index 99d2ffc00..47f1453be 100644
--- a/src/src/expand.c
+++ b/src/src/expand.c
@@ -5307,9 +5307,25 @@ while (*s != 0)
       int save_expand_nmax =
         save_expand_strings(save_expand_nstring, save_expand_nlength);
 
-      /* Read the arguments */
+      /* While skipping we cannot rely on the data for expansions being
+      available (eg. $item) hence cannot decide on numeric vs. keyed.
+      Just read as many arguments as there are. */
 
-      for (i = 0; i < j; i++)
+      if (skipping)
+	{
+        while (isspace(*s)) s++;
+        while (*s == '{')
+	  {
+          if (!expand_string_internal(s+1, TRUE, &s, skipping, TRUE, &resetok))
+	    goto EXPAND_FAILED;					/*{*/
+          if (*s++ != '}') goto EXPAND_FAILED_CURLY;
+	  while (isspace(*s)) s++;
+	  }
+	if (*s != '}')
+	  goto EXPAND_FAILED_CURLY;
+	}
+
+      else for (i = 0; i < j; i++) /* Read the proper number of arguments */
         {
         while (isspace(*s)) s++;
         if (*s == '{') 						/*}*/
@@ -5336,27 +5352,24 @@ while (*s != 0)
             while (len > 0 && isspace(p[len-1])) len--;
             p[len] = 0;
 
-            if (!skipping)
+	    if (*p == 0)
 	      {
-	      if (*p == 0)
-		{
-		expand_string_message = US"first argument of \"extract\" must "
-		  "not be empty";
-		goto EXPAND_FAILED;
-		}
+	      expand_string_message = US"first argument of \"extract\" must "
+		"not be empty";
+	      goto EXPAND_FAILED;
+	      }
 
-	      if (*p == '-')
-		{
-		field_number = -1;
-		p++;
-		}
-	      while (*p != 0 && isdigit(*p)) x = x * 10 + *p++ - '0';
-	      if (*p == 0)
-		{
-		field_number *= x;
-		j = 3;               /* Need 3 args */
-		field_number_set = TRUE;
-		}
+	    if (*p == '-')
+	      {
+	      field_number = -1;
+	      p++;
+	      }
+	    while (*p != 0 && isdigit(*p)) x = x * 10 + *p++ - '0';
+	    if (*p == 0)
+	      {
+	      field_number *= x;
+	      j = 3;               /* Need 3 args */
+	      field_number_set = TRUE;
 	      }
             }
           }
diff --git a/test/scripts/0000-Basic/0002 b/test/scripts/0000-Basic/0002
index 105134da3..bc61998ca 100644
--- a/test/scripts/0000-Basic/0002
+++ b/test/scripts/0000-Basic/0002
@@ -615,6 +615,9 @@ ${extract{}{X=3}}
 ${extract{ }{X=3}}
 ${extract{ 2 }{ }{a b c}}
 
+${map{a,1:b,2:c,3}{${extract{1}{,}{$item}{$value}{}}}}
+${map{a,1:b,2:c,3}{${extract{1}{,}{$item}{$value}{failcase}{bogus_argument}}}}
+
 # Translation
 
 abcdea aaa xyz ${tr{abcdea}{aaa}{xyz}}
diff --git a/test/stdout/0002 b/test/stdout/0002
index ee351a278..ee1ef9d93 100644
--- a/test/stdout/0002
+++ b/test/stdout/0002
@@ -577,6 +577,9 @@
 > Failed: first argument of "extract" must not be empty
 > b
 > 
+> a:b:c
+> Failed: missing or misplaced { or } inside "map" item
+> 
 > # Translation
 > 
 > abcdea aaa xyz zbcdez