Add errhint_plural() function and make use of it

Similar to existing errmsg_plural() and errdetail_plural().  Some
errhint() calls hadn't received the proper plural treatment yet.

doc/src/sgml/sources.sgml

@@ -282,6 +282,14 @@ ereport(ERROR,
      <function>errmsg</function>.
     </para>
    </listitem>
+   <listitem>
+    <para>
+     <function>errhint_plural(const char *fmt_singular, const char *fmt_plural,
+     unsigned long n, ...)</function> is like <function>errhint</function>, but with
+     support for various plural forms of the message.
+     For more information see <xref linkend="nls-guidelines"/>.
+    </para>
+   </listitem>
    <listitem>
     <para>
      <function>errcontext(const char *msg, ...)</function> is not normally called

src/backend/parser/parse_func.c

@@ -417,9 +417,11 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 									func_signature_string(funcname, nargs,
 														  argnames,
 														  actual_arg_types)),
-							 errhint("There is an ordered-set aggregate %s, but it requires %d direct arguments, not %d.",
-									 NameListToString(funcname),
-									 catDirectArgs, numDirectArgs),
+							 errhint_plural("There is an ordered-set aggregate %s, but it requires %d direct argument, not %d.",
+											"There is an ordered-set aggregate %s, but it requires %d direct arguments, not %d.",
+											catDirectArgs,
+											NameListToString(funcname),
+											catDirectArgs, numDirectArgs),
 							 parser_errposition(pstate, location)));
 			}
 			else
@@ -446,9 +448,11 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 										func_signature_string(funcname, nargs,
 															  argnames,
 															  actual_arg_types)),
-								 errhint("There is an ordered-set aggregate %s, but it requires %d direct arguments, not %d.",
-										 NameListToString(funcname),
-										 catDirectArgs, numDirectArgs),
+								 errhint_plural("There is an ordered-set aggregate %s, but it requires %d direct argument, not %d.",
+												"There is an ordered-set aggregate %s, but it requires %d direct arguments, not %d.",
+												catDirectArgs,
+												NameListToString(funcname),
+												catDirectArgs, numDirectArgs),
 								 parser_errposition(pstate, location)));
 				}
 				else
@@ -485,9 +489,11 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 											func_signature_string(funcname, nargs,
 																  argnames,
 																  actual_arg_types)),
-									 errhint("There is an ordered-set aggregate %s, but it requires at least %d direct arguments.",
-											 NameListToString(funcname),
-											 catDirectArgs),
+									 errhint_plural("There is an ordered-set aggregate %s, but it requires at least %d direct argument.",
+													"There is an ordered-set aggregate %s, but it requires at least %d direct arguments.",
+													catDirectArgs,
+													NameListToString(funcname),
+													catDirectArgs),
 									 parser_errposition(pstate, location)));
 					}
 				}

src/backend/utils/error/elog.c

@@ -1166,6 +1166,29 @@ errhint(const char *fmt,...)
 }
 
 
+/*
+ * errhint_plural --- add a hint error message text to the current error,
+ * with support for pluralization of the message text
+ */
+int
+errhint_plural(const char *fmt_singular, const char *fmt_plural,
+			   unsigned long n,...)
+{
+	ErrorData  *edata = &errordata[errordata_stack_depth];
+	MemoryContext oldcontext;
+
+	recursion_depth++;
+	CHECK_STACK_DEPTH();
+	oldcontext = MemoryContextSwitchTo(edata->assoc_context);
+
+	EVALUATE_MESSAGE_PLURAL(edata->domain, hint, false);
+
+	MemoryContextSwitchTo(oldcontext);
+	recursion_depth--;
+	return 0;					/* return value does not matter */
+}
+
+
 /*
  * errcontext_msg --- add a context error message text to the current error
  *

src/include/utils/elog.h

@@ -188,6 +188,9 @@ extern int	errdetail_plural(const char *fmt_singular, const char *fmt_plural,
 
 extern int	errhint(const char *fmt,...) pg_attribute_printf(1, 2);
 
+extern int	errhint_plural(const char *fmt_singular, const char *fmt_plural,
+						   unsigned long n,...) pg_attribute_printf(1, 4) pg_attribute_printf(2, 4);
+
 /*
  * errcontext() is typically called in error context callback functions, not
  * within an ereport() invocation. The callback function can be in a different

src/nls-global.mk

@@ -57,7 +57,7 @@ BACKEND_COMMON_GETTEXT_TRIGGERS = \
     $(FRONTEND_COMMON_GETTEXT_TRIGGERS) \
     errmsg errmsg_plural:1,2 \
     errdetail errdetail_log errdetail_plural:1,2 \
-    errhint \
+    errhint errhint_plural:1,2 \
     errcontext \
     XactLockTableWait:4 \
     MultiXactIdWait:6 \
@@ -66,7 +66,7 @@ BACKEND_COMMON_GETTEXT_FLAGS = \
     $(FRONTEND_COMMON_GETTEXT_FLAGS) \
     errmsg:1:c-format errmsg_plural:1:c-format errmsg_plural:2:c-format \
     errdetail:1:c-format errdetail_log:1:c-format errdetail_plural:1:c-format errdetail_plural:2:c-format \
-    errhint:1:c-format \
+    errhint:1:c-format errhint_plural:1:c-format errhint_plural:2:c-format \
     errcontext:1:c-format
 
 FRONTEND_COMMON_GETTEXT_FILES = $(top_srcdir)/src/common/logging.c