Fix plpgsql to not lookup block labels except in contexts where a block label

is sane (eg, EXIT argument or first part of a qualified identifier), and cause
more-closely-nested record variables to take precedence over outer block
labels.  This cures the breakage exhibited by Marko Kreen that 8.3 no longer
allowed a function's name to be used for a variable within the function, and
makes plpgsql's handling of block labels more like Oracle's.  It's important
to fix this now because we are documenting the use of block labels as variable
qualifiers for the first time in 8.3.

src/pl/plpgsql/src/gram.y

@@ -9,7 +9,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/pl/plpgsql/src/gram.y,v 1.106 2007/11/09 23:58:32 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/pl/plpgsql/src/gram.y,v 1.107 2007/11/27 19:58:44 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -43,6 +43,7 @@ static PLpgSQL_row		*make_scalar_list1(const char *initial_name,
 										   int lineno);
 static	void			 check_sql_expr(const char *stmt);
 static	void			 plpgsql_sql_error_callback(void *arg);
+static	char			*check_label(const char *yytxt);
 static	void			 check_labels(const char *start_label,
 									  const char *end_label);
 
@@ -214,7 +215,6 @@ static	void			 check_labels(const char *start_label,
 %token	T_ROW
 %token	T_RECORD
 %token	T_DTYPE
-%token	T_LABEL
 %token	T_WORD
 %token	T_ERROR
 
@@ -505,7 +505,8 @@ decl_aliasitem	: T_WORD
 							yyerror("only positional parameters can be aliased");
 
 						plpgsql_ns_setlocal(false);
-						nsi = plpgsql_ns_lookup(name, NULL);
+
+						nsi = plpgsql_ns_lookup(name, NULL, NULL, NULL);
 						if (nsi == NULL)
 						{
 							plpgsql_error_lineno = plpgsql_scanner_lineno();
@@ -1642,20 +1643,28 @@ opt_block_label	:
 					}
 				;
 
+/*
+ * need all the options because scanner will have tried to resolve as variable
+ */
 opt_label	:
 					{
 						$$ = NULL;
 					}
-				| T_LABEL
+				| T_WORD
+					{
+						$$ = check_label(yytext);
+					}
+				| T_SCALAR
 					{
-						char *label_name;
-						plpgsql_convert_ident(yytext, &label_name, 1);
-						$$ = label_name;
+						$$ = check_label(yytext);
 					}
-				| T_WORD
+				| T_RECORD
 					{
-						/* just to give a better error than "syntax error" */
-						yyerror("no such label");
+						$$ = check_label(yytext);
+					}
+				| T_ROW
+					{
+						$$ = check_label(yytext);
 					}
 				;
 
@@ -2484,6 +2493,17 @@ plpgsql_sql_error_callback(void *arg)
 	errposition(0);
 }
 
+static char *
+check_label(const char *yytxt)
+{
+	char	   *label_name;
+
+	plpgsql_convert_ident(yytxt, &label_name, 1);
+	if (plpgsql_ns_lookup_label(label_name) == NULL)
+		yyerror("no such label");
+	return label_name;
+}
+
 static void
 check_labels(const char *start_label, const char *end_label)
 {

src/pl/plpgsql/src/pl_funcs.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/pl/plpgsql/src/pl_funcs.c,v 1.65 2007/11/15 22:25:17 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/pl/plpgsql/src/pl_funcs.c,v 1.66 2007/11/27 19:58:44 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -126,9 +126,15 @@ plpgsql_ns_init(void)
 
 
 /* ----------
- * plpgsql_ns_setlocal			Tell plpgsql_ns_lookup to or to
- *					not look into the current level
- *					only.
+ * plpgsql_ns_setlocal			Tell plpgsql_ns_lookup whether to
+ *					look into the current level only.
+ *
+ * This is a crock, but in the current design we need it because scan.l
+ * initiates name lookup, and the scanner does not know whether we are
+ * examining a name being declared in a DECLARE section.  For that case
+ * we only want to know if there is a conflicting name earlier in the
+ * same DECLARE section.  So the grammar must temporarily set local mode
+ * before scanning decl_varnames.
  * ----------
  */
 bool
@@ -219,59 +225,98 @@ plpgsql_ns_additem(int itemtype, int itemno, const char *name)
 
 
 /* ----------
- * plpgsql_ns_lookup			Lookup for a word in the namestack
+ * plpgsql_ns_lookup			Lookup an identifier in the namestack
+ *
+ * Note that this only searches for variables, not labels.
+ *
+ * name1 must be non-NULL.  Pass NULL for name2 and/or name3 if parsing a name
+ * with fewer than three components.
+ *
+ * If names_used isn't NULL, *names_used receives the number of names
+ * matched: 0 if no match, 1 if name1 matched an unqualified variable name,
+ * 2 if name1 and name2 matched a block label + variable name.
+ *
+ * Note that name3 is never directly matched to anything.  However, if it
+ * isn't NULL, we will disregard qualified matches to scalar variables.
+ * Similarly, if name2 isn't NULL, we disregard unqualified matches to
+ * scalar variables.
  * ----------
  */
 PLpgSQL_nsitem *
-plpgsql_ns_lookup(const char *name, const char *label)
+plpgsql_ns_lookup(const char *name1, const char *name2, const char *name3,
+				  int *names_used)
 {
 	PLpgSQL_ns *ns;
 	int			i;
 
-	/*
-	 * If a label is specified, lookup only in that
-	 */
-	if (label != NULL)
+	/* Scan each level of the namestack */
+	for (ns = ns_current; ns != NULL; ns = ns->upper)
 	{
-		for (ns = ns_current; ns != NULL; ns = ns->upper)
+		/* Check for unqualified match to variable name */
+		for (i = 1; i < ns->items_used; i++)
+		{
+			PLpgSQL_nsitem *nsitem = ns->items[i];
+
+			if (strcmp(nsitem->name, name1) == 0)
+			{
+				if (name2 == NULL ||
+					nsitem->itemtype != PLPGSQL_NSTYPE_VAR)
+				{
+					if (names_used)
+						*names_used = 1;
+					return nsitem;
+				}
+			}
+		}
+
+		/* Check for qualified match to variable name */
+		if (name2 != NULL &&
+			strcmp(ns->items[0]->name, name1) == 0)
 		{
-			if (strcmp(ns->items[0]->name, label) == 0)
+			for (i = 1; i < ns->items_used; i++)
 			{
-				for (i = 1; i < ns->items_used; i++)
+				PLpgSQL_nsitem *nsitem = ns->items[i];
+
+				if (strcmp(nsitem->name, name2) == 0)
 				{
-					if (strcmp(ns->items[i]->name, name) == 0)
-						return ns->items[i];
+					if (name3 == NULL ||
+						nsitem->itemtype != PLPGSQL_NSTYPE_VAR)
+					{
+						if (names_used)
+							*names_used = 2;
+						return nsitem;
+					}
 				}
-				return NULL;	/* name not found in specified label */
 			}
 		}
-		return NULL;			/* label not found */
+
+		if (ns_localmode)
+			break;				/* do not look into upper levels */
 	}
 
-	/*
-	 * No label given, lookup for visible labels ignoring localmode
-	 */
+	/* This is just to suppress possibly-uninitialized-variable warnings */
+	if (names_used)
+		*names_used = 0;
+	return NULL;				/* No match found */
+}
+
+
+/* ----------
+ * plpgsql_ns_lookup_label		Lookup a label in the namestack
+ * ----------
+ */
+PLpgSQL_nsitem *
+plpgsql_ns_lookup_label(const char *name)
+{
+	PLpgSQL_ns *ns;
+
 	for (ns = ns_current; ns != NULL; ns = ns->upper)
 	{
 		if (strcmp(ns->items[0]->name, name) == 0)
 			return ns->items[0];
 	}
 
-	/*
-	 * Finally lookup name in the namestack
-	 */
-	for (ns = ns_current; ns != NULL; ns = ns->upper)
-	{
-		for (i = 1; i < ns->items_used; i++)
-		{
-			if (strcmp(ns->items[i]->name, name) == 0)
-				return ns->items[i];
-		}
-		if (ns_localmode)
-			return NULL;		/* name not found in current namespace */
-	}
-
-	return NULL;
+	return NULL;				/* label not found */
 }
 
 
@@ -846,8 +891,9 @@ static void
 dump_exit(PLpgSQL_stmt_exit *stmt)
 {
 	dump_ind();
-	printf("%s label='%s'",
-		   stmt->is_exit ? "EXIT" : "CONTINUE", stmt->label);
+	printf("%s", stmt->is_exit ? "EXIT" : "CONTINUE");
+	if (stmt->label != NULL)
+		printf(" label='%s'", stmt->label);
 	if (stmt->cond != NULL)
 	{
 		printf(" WHEN ");

src/pl/plpgsql/src/plpgsql.h

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/pl/plpgsql/src/plpgsql.h,v 1.93 2007/11/15 22:25:17 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/pl/plpgsql/src/plpgsql.h,v 1.94 2007/11/27 19:58:44 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -473,7 +473,7 @@ typedef struct
 	int			cmd_type;
 	int			lineno;
 	bool		is_exit;		/* Is this an exit or a continue? */
-	char	   *label;
+	char	   *label;			/* NULL if it's an unlabelled EXIT/CONTINUE */
 	PLpgSQL_expr *cond;
 } PLpgSQL_stmt_exit;
 
@@ -723,9 +723,9 @@ extern PLpgSQL_plugin **plugin_ptr;
  */
 extern PLpgSQL_function *plpgsql_compile(FunctionCallInfo fcinfo,
 				bool forValidator);
-extern int	plpgsql_parse_word(char *word);
-extern int	plpgsql_parse_dblword(char *word);
-extern int	plpgsql_parse_tripword(char *word);
+extern int	plpgsql_parse_word(const char *word);
+extern int	plpgsql_parse_dblword(const char *word);
+extern int	plpgsql_parse_tripword(const char *word);
 extern int	plpgsql_parse_wordtype(char *word);
 extern int	plpgsql_parse_dblwordtype(char *word);
 extern int	plpgsql_parse_tripwordtype(char *word);
@@ -773,7 +773,7 @@ extern void plpgsql_dstring_append_char(PLpgSQL_dstring *ds, char c);
 extern char *plpgsql_dstring_get(PLpgSQL_dstring *ds);
 
 /* ----------
- * Functions for the namestack handling in pl_funcs.c
+ * Functions for namestack handling in pl_funcs.c
  * ----------
  */
 extern void plpgsql_ns_init(void);
@@ -781,7 +781,9 @@ extern bool plpgsql_ns_setlocal(bool flag);
 extern void plpgsql_ns_push(const char *label);
 extern void plpgsql_ns_pop(void);
 extern void plpgsql_ns_additem(int itemtype, int itemno, const char *name);
-extern PLpgSQL_nsitem *plpgsql_ns_lookup(const char *name, const char *nsname);
+extern PLpgSQL_nsitem *plpgsql_ns_lookup(const char *name1, const char *name2,
+										 const char *name3, int *names_used);
+extern PLpgSQL_nsitem *plpgsql_ns_lookup_label(const char *name);
 extern void plpgsql_ns_rename(char *oldname, char *newname);
 
 /* ----------