Convert enum_in() to report errors softly.

I missed this in my initial survey, probably because I examined
the contents of pg_type in the postgres database, which lacks
any enumerated types.

Discussion: https://postgr.es/m/CAAJ_b97KeDWUdpTKGOaFYPv0OicjOu6EW+QYWj-Ywrgj_aEy1g@mail.gmail.com

src/backend/utils/adt/enum.c

@@ -110,12 +110,13 @@ enum_in(PG_FUNCTION_ARGS)
 {
 	char	   *name = PG_GETARG_CSTRING(0);
 	Oid			enumtypoid = PG_GETARG_OID(1);
+	Node	   *escontext = fcinfo->context;
 	Oid			enumoid;
 	HeapTuple	tup;
 
 	/* must check length to prevent Assert failure within SearchSysCache */
 	if (strlen(name) >= NAMEDATALEN)
-		ereport(ERROR,
+		ereturn(escontext, (Datum) 0,
 				(errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
 				 errmsg("invalid input value for enum %s: \"%s\"",
 						format_type_be(enumtypoid),
@@ -125,13 +126,18 @@ enum_in(PG_FUNCTION_ARGS)
 						  ObjectIdGetDatum(enumtypoid),
 						  CStringGetDatum(name));
 	if (!HeapTupleIsValid(tup))
-		ereport(ERROR,
+		ereturn(escontext, (Datum) 0,
 				(errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
 				 errmsg("invalid input value for enum %s: \"%s\"",
 						format_type_be(enumtypoid),
 						name)));
 
-	/* check it's safe to use in SQL */
+	/*
+	 * Check it's safe to use in SQL.  Perhaps we should take the trouble to
+	 * report "unsafe use" softly; but it's unclear that it's worth the
+	 * trouble, or indeed that that is a legitimate bad-input case at all
+	 * rather than an implementation shortcoming.
+	 */
 	check_safe_enum_use(tup);
 
 	/*

src/test/regress/expected/enum.out

@@ -24,6 +24,31 @@ SELECT 'mauve'::rainbow;
 ERROR:  invalid input value for enum rainbow: "mauve"
 LINE 1: SELECT 'mauve'::rainbow;
                ^
+-- Also try it with non-error-throwing API
+SELECT pg_input_is_valid('red', 'rainbow');
+ pg_input_is_valid 
+-------------------
+ t
+(1 row)
+
+SELECT pg_input_is_valid('mauve', 'rainbow');
+ pg_input_is_valid 
+-------------------
+ f
+(1 row)
+
+SELECT pg_input_error_message('mauve', 'rainbow');
+            pg_input_error_message             
+-----------------------------------------------
+ invalid input value for enum rainbow: "mauve"
+(1 row)
+
+SELECT pg_input_error_message(repeat('too_long', 32), 'rainbow');
+                                                                                                                                          pg_input_error_message                                                                                                                                          
+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
+ invalid input value for enum rainbow: "too_longtoo_longtoo_longtoo_longtoo_longtoo_longtoo_longtoo_longtoo_longtoo_longtoo_longtoo_longtoo_longtoo_longtoo_longtoo_longtoo_longtoo_longtoo_longtoo_longtoo_longtoo_longtoo_longtoo_longtoo_longtoo_longtoo_longtoo_longtoo_longtoo_longtoo_longtoo_long"
+(1 row)
+
 --
 -- adding new values
 --

src/test/regress/sql/enum.sql

@@ -15,6 +15,12 @@ SELECT COUNT(*) FROM pg_enum WHERE enumtypid = 'rainbow'::regtype;
 SELECT 'red'::rainbow;
 SELECT 'mauve'::rainbow;
 
+-- Also try it with non-error-throwing API
+SELECT pg_input_is_valid('red', 'rainbow');
+SELECT pg_input_is_valid('mauve', 'rainbow');
+SELECT pg_input_error_message('mauve', 'rainbow');
+SELECT pg_input_error_message(repeat('too_long', 32), 'rainbow');
+
 --
 -- adding new values
 --