Improve plpgsql parsing to report "foo is not a known variable", rather than a

generic syntax error, when seeing "foo := something" and foo isn't recognized.
This buys back most of the helpfulness discarded in my previous patch by not
throwing errors when a qualified name appears to match a row variable but the
last component doesn't match any field of the row.  It covers other cases
where our error messages left something to be desired, too.

diff --git a/src/pl/plpgsql/src/gram.y b/src/pl/plpgsql/src/gram.y
index 77afcbec8bb5ed4d82fef20eed3ff1525d9ea4e7..c4e3c128346ba05ee05ee91ad4caa562fe44ec68 100644 (file)
--- a/src/pl/plpgsql/src/gram.y
+++ b/src/pl/plpgsql/src/gram.y
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *   $PostgreSQL: pgsql/src/pl/plpgsql/src/gram.y,v 1.138 2010/01/10 17:15:18 tgl Exp $
+ *   $PostgreSQL: pgsql/src/pl/plpgsql/src/gram.y,v 1.139 2010/01/10 17:56:50 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -56,7 +56,9 @@ union YYSTYPE;                    /* need forward reference for tok_is_keyword */
 
 static bool            tok_is_keyword(int token, union YYSTYPE *lval,
                                       int kw_token, const char *kw_str);
-static void            token_is_not_variable(int tok);
+static void            word_is_not_variable(PLword *word, int location);
+static void            cword_is_not_variable(PLcword *cword, int location);
+static void            current_token_is_not_variable(int tok);
 static PLpgSQL_expr    *read_sql_construct(int until,
                                            int until2,
                                            int until3,
@@ -851,12 +853,12 @@ getdiag_target    : T_DATUM
                | T_WORD
                    {
                        /* just to give a better message than "syntax error" */
-                       token_is_not_variable(T_WORD);
+                       word_is_not_variable(&($1), @1);
                    }
                | T_CWORD
                    {
                        /* just to give a better message than "syntax error" */
-                       token_is_not_variable(T_CWORD);
+                       cword_is_not_variable(&($1), @1);
                    }
                ;
 
@@ -1371,19 +1373,12 @@ for_variable    : T_DATUM
                        tok = yylex();
                        plpgsql_push_back_token(tok);
                        if (tok == ',')
-                       {
-                           /* can't use token_is_not_variable here */
-                           ereport(ERROR,
-                                   (errcode(ERRCODE_SYNTAX_ERROR),
-                                    errmsg("\"%s\" is not a known variable",
-                                           $1.ident),
-                                    parser_errposition(@1)));
-                       }
+                           word_is_not_variable(&($1), @1);
                    }
                | T_CWORD
                    {
                        /* just to give a better message than "syntax error" */
-                       token_is_not_variable(T_CWORD);
+                       cword_is_not_variable(&($1), @1);
                    }
                ;
 
@@ -1587,15 +1582,38 @@ loop_body       : proc_sect K_END K_LOOP opt_label ';'
 
 /*
  * T_WORD+T_CWORD match any initial identifier that is not a known plpgsql
- * variable.  The composite case is probably a syntax error, but we'll let
- * the core parser decide that.
+ * variable.  (The composite case is probably a syntax error, but we'll let
+ * the core parser decide that.)  Normally, we should assume that such a
+ * word is a SQL statement keyword that isn't also a plpgsql keyword.
+ * However, if the next token is assignment or '[', it can't be a valid
+ * SQL statement, and what we're probably looking at is an intended variable
+ * assignment.  Give an appropriate complaint for that, instead of letting
+ * the core parser throw an unhelpful "syntax error".
  */
 stmt_execsql   : K_INSERT
-                   { $$ = make_execsql_stmt(K_INSERT, @1); }
+                   {
+                       $$ = make_execsql_stmt(K_INSERT, @1);
+                   }
                | T_WORD
-                   { $$ = make_execsql_stmt(T_WORD, @1); }
+                   {
+                       int         tok;
+
+                       tok = yylex();
+                       plpgsql_push_back_token(tok);
+                       if (tok == '=' || tok == COLON_EQUALS || tok == '[')
+                           word_is_not_variable(&($1), @1);
+                       $$ = make_execsql_stmt(T_WORD, @1);
+                   }
                | T_CWORD
-                   { $$ = make_execsql_stmt(T_CWORD, @1); }
+                   {
+                       int         tok;
+
+                       tok = yylex();
+                       plpgsql_push_back_token(tok);
+                       if (tok == '=' || tok == COLON_EQUALS || tok == '[')
+                           cword_is_not_variable(&($1), @1);
+                       $$ = make_execsql_stmt(T_CWORD, @1);
+                   }
                ;
 
 stmt_dynexecute : K_EXECUTE
@@ -1793,12 +1811,12 @@ cursor_variable : T_DATUM
                | T_WORD
                    {
                        /* just to give a better message than "syntax error" */
-                       token_is_not_variable(T_WORD);
+                       word_is_not_variable(&($1), @1);
                    }
                | T_CWORD
                    {
                        /* just to give a better message than "syntax error" */
-                       token_is_not_variable(T_CWORD);
+                       cword_is_not_variable(&($1), @1);
                    }
                ;
 
@@ -2045,26 +2063,43 @@ tok_is_keyword(int token, union YYSTYPE *lval,
    return false;               /* not the keyword */
 }
 
+/*
+ * Convenience routine to complain when we expected T_DATUM and got T_WORD,
+ * ie, unrecognized variable.
+ */
+static void
+word_is_not_variable(PLword *word, int location)
+{
+   ereport(ERROR,
+           (errcode(ERRCODE_SYNTAX_ERROR),
+            errmsg("\"%s\" is not a known variable",
+                   word->ident),
+            parser_errposition(location)));
+}
+
+/* Same, for a CWORD */
+static void
+cword_is_not_variable(PLcword *cword, int location)
+{
+   ereport(ERROR,
+           (errcode(ERRCODE_SYNTAX_ERROR),
+            errmsg("\"%s\" is not a known variable",
+                   NameListToString(cword->idents)),
+            parser_errposition(location)));
+}
+
 /*
  * Convenience routine to complain when we expected T_DATUM and got
  * something else.  "tok" must be the current token, since we also
  * look at yylval and yylloc.
  */
 static void
-token_is_not_variable(int tok)
+current_token_is_not_variable(int tok)
 {
    if (tok == T_WORD)
-       ereport(ERROR,
-               (errcode(ERRCODE_SYNTAX_ERROR),
-                errmsg("\"%s\" is not a known variable",
-                       yylval.word.ident),
-                parser_errposition(yylloc)));
+       word_is_not_variable(&(yylval.word), yylloc);
    else if (tok == T_CWORD)
-       ereport(ERROR,
-               (errcode(ERRCODE_SYNTAX_ERROR),
-                errmsg("\"%s\" is not a known variable",
-                       NameListToString(yylval.cword.idents)),
-                parser_errposition(yylloc)));
+       cword_is_not_variable(&(yylval.cword), yylloc);
    else
        yyerror("syntax error");
 }
@@ -2848,7 +2883,7 @@ read_into_target(PLpgSQL_rec **rec, PLpgSQL_row **row, bool *strict)
 
        default:
            /* just to give a better message than "syntax error" */
-           token_is_not_variable(tok);
+           current_token_is_not_variable(tok);
    }
 }
 
@@ -2901,7 +2936,7 @@ read_into_scalar_list(char *initial_name,
 
            default:
                /* just to give a better message than "syntax error" */
-               token_is_not_variable(tok);
+               current_token_is_not_variable(tok);
        }
    }