Add test scaffolding for soft error reporting from input functions.

pg_input_is_valid() returns boolean, while pg_input_error_message()
returns the primary error message if the input is bad, or NULL
if the input is OK.  The main reason for having two functions is
so that we can test both the details-wanted and the no-details-wanted
code paths.

Although these are primarily designed with testing in mind,
it could well be that they'll be useful to end users as well.

This patch is mostly by me, but it owes very substantial debt to
earlier work by Nikita Glukhov, Andrew Dunstan, and Amul Sul.
Thanks to Andres Freund for review.

Discussion: https://postgr.es/m/3bbbb0df-7382-bf87-9737-340ba096e034@postgrespro.ru

1 files changed, 129 insertions, 0 deletions

diff --git a/src/backend/utils/adt/misc.c b/src/backend/utils/adt/misc.c
index 9c13251231..d678d28600 100644
--- a/src/backend/utils/adt/misc.c
+++ b/src/backend/utils/adt/misc.c
@@ -32,6 +32,8 @@
 #include "common/keywords.h"
 #include "funcapi.h"
 #include "miscadmin.h"
+#include "nodes/miscnodes.h"
+#include "parser/parse_type.h"
 #include "parser/scansup.h"
 #include "pgstat.h"
 #include "postmaster/syslogger.h"
@@ -45,6 +47,25 @@
 #include "utils/ruleutils.h"
 #include "utils/timestamp.h"
 
+
+/*
+ * structure to cache metadata needed in pg_input_is_valid_common
+ */
+typedef struct ValidIOData
+{
+	Oid			typoid;
+	int32		typmod;
+	bool		typname_constant;
+	Oid			typiofunc;
+	Oid			typioparam;
+	FmgrInfo	inputproc;
+} ValidIOData;
+
+static bool pg_input_is_valid_common(FunctionCallInfo fcinfo,
+									 text *txt, text *typname,
+									 ErrorSaveContext *escontext);
+
+
 /*
  * Common subroutine for num_nulls() and num_nonnulls().
  * Returns true if successful, false if function should return NULL.
@@ -641,6 +662,114 @@ pg_column_is_updatable(PG_FUNCTION_ARGS)
 
 
 /*
+ * pg_input_is_valid - test whether string is valid input for datatype.
+ *
+ * Returns true if OK, false if not.
+ *
+ * This will only work usefully if the datatype's input function has been
+ * updated to return "soft" errors via errsave/ereturn.
+ */
+Datum
+pg_input_is_valid(PG_FUNCTION_ARGS)
+{
+	text	   *txt = PG_GETARG_TEXT_PP(0);
+	text	   *typname = PG_GETARG_TEXT_PP(1);
+	ErrorSaveContext escontext = {T_ErrorSaveContext};
+
+	PG_RETURN_BOOL(pg_input_is_valid_common(fcinfo, txt, typname,
+											&escontext));
+}
+
+/*
+ * pg_input_error_message - test whether string is valid input for datatype.
+ *
+ * Returns NULL if OK, else the primary message string from the error.
+ *
+ * This will only work usefully if the datatype's input function has been
+ * updated to return "soft" errors via errsave/ereturn.
+ */
+Datum
+pg_input_error_message(PG_FUNCTION_ARGS)
+{
+	text	   *txt = PG_GETARG_TEXT_PP(0);
+	text	   *typname = PG_GETARG_TEXT_PP(1);
+	ErrorSaveContext escontext = {T_ErrorSaveContext};
+
+	/* Enable details_wanted */
+	escontext.details_wanted = true;
+
+	if (pg_input_is_valid_common(fcinfo, txt, typname,
+								 &escontext))
+		PG_RETURN_NULL();
+
+	Assert(escontext.error_occurred);
+	Assert(escontext.error_data != NULL);
+	Assert(escontext.error_data->message != NULL);
+
+	PG_RETURN_TEXT_P(cstring_to_text(escontext.error_data->message));
+}
+
+/* Common subroutine for the above */
+static bool
+pg_input_is_valid_common(FunctionCallInfo fcinfo,
+						 text *txt, text *typname,
+						 ErrorSaveContext *escontext)
+{
+	char	   *str = text_to_cstring(txt);
+	ValidIOData *my_extra;
+	Datum		converted;
+
+	/*
+	 * We arrange to look up the needed I/O info just once per series of
+	 * calls, assuming the data type doesn't change underneath us.
+	 */
+	my_extra = (ValidIOData *) fcinfo->flinfo->fn_extra;
+	if (my_extra == NULL)
+	{
+		fcinfo->flinfo->fn_extra =
+			MemoryContextAlloc(fcinfo->flinfo->fn_mcxt,
+							   sizeof(ValidIOData));
+		my_extra = (ValidIOData *) fcinfo->flinfo->fn_extra;
+		my_extra->typoid = InvalidOid;
+		/* Detect whether typname argument is constant. */
+		my_extra->typname_constant = get_fn_expr_arg_stable(fcinfo->flinfo, 1);
+	}
+
+	/*
+	 * If the typname argument is constant, we only need to parse it the first
+	 * time through.
+	 */
+	if (my_extra->typoid == InvalidOid || !my_extra->typname_constant)
+	{
+		char	   *typnamestr = text_to_cstring(typname);
+		Oid			typoid;
+
+		/* Parse type-name argument to obtain type OID and encoded typmod. */
+		parseTypeString(typnamestr, &typoid, &my_extra->typmod, false);
+
+		/* Update type-specific info if typoid changed. */
+		if (my_extra->typoid != typoid)
+		{
+			getTypeInputInfo(typoid,
+							 &my_extra->typiofunc,
+							 &my_extra->typioparam);
+			fmgr_info_cxt(my_extra->typiofunc, &my_extra->inputproc,
+						  fcinfo->flinfo->fn_mcxt);
+			my_extra->typoid = typoid;
+		}
+	}
+
+	/* Now we can try to perform the conversion. */
+	return InputFunctionCallSafe(&my_extra->inputproc,
+								 str,
+								 my_extra->typioparam,
+								 my_extra->typmod,
+								 (Node *) escontext,
+								 &converted);
+}
+
+
+/*
  * Is character a valid identifier start?
  * Must match scan.l's {ident_start} character class.
  */