enhance message of unmodified OUT variables when was used RETURN QUER…

…Y EXECUTE command

src/check_function.c

@@ -1042,6 +1042,7 @@ plpgsql_check_setup_cstate(PLpgSQL_checkstate *cstate,
 #endif
 
 	cstate->found_return_query = false;
+	cstate->found_return_dyn_query = false;
 
 	cstate->fake_rtd = fake_rtd;
 

src/plpgsql_check.h

@@ -96,6 +96,7 @@ typedef struct PLpgSQL_checkstate
 	Bitmapset  *modif_variables;			/* track which variables had been changed; bit per varno */
 	PLpgSQL_stmt_stack_item *top_stmt_stack;	/* list of known labels + related command */
 	bool		found_return_query;			/* true, when code contains RETURN query */
+	bool		found_return_dyn_query;		/* true, when code contains RETURN QUERY EXECUTE */
 	Bitmapset	   *func_oids;				/* list of used (and displayed) functions */
 	Bitmapset	   *rel_oids;				/* list of used (and displayed) relations */
 	bool		fake_rtd;					/* true when functions returns record */
@@ -324,6 +325,7 @@ extern plpgsql_check__recognize_err_condition_t plpgsql_check__recognize_err_con
 #define UNUSED_PARAMETER_TEXT			"unused parameter \"%s\""
 #define NEVER_READ_PARAMETER_TEXT		"parameter \"%s\" is never read"
 #define UNMODIFIED_VARIABLE_TEXT		"unmodified OUT variable \"%s\""
+#define MAYBE_UNMODIFIED_VARIABLE_TEXT	"OUT variable \"%s\" is maybe unmodified"
 #define OUT_COMPOSITE_IS_NOT_SINGLE_TEXT	"composite OUT variable \"%s\" is not single argument"
 #define UNSAFE_EXECUTE					"the expression used by EXECUTE command is possibly sql injection vulnerable"
 

src/report.c

@@ -357,12 +357,18 @@ plpgsql_check_report_unused_variables(PLpgSQL_checkstate *cstate)
 
 					if (!datum_is_used(cstate, varno2, true))
 					{
+						const char *fmt = cstate->found_return_dyn_query ?
+								  MAYBE_UNMODIFIED_VARIABLE_TEXT : UNMODIFIED_VARIABLE_TEXT;
+
+						const char *detail = cstate->found_return_dyn_query ?
+								  "cannot to determine result of dynamic SQL" : NULL;
+
 						initStringInfo(&message);
-						appendStringInfo(&message, UNMODIFIED_VARIABLE_TEXT, var->refname);
+						appendStringInfo(&message, fmt, var->refname);
 						plpgsql_check_put_error(cstate,
 								  0, 0,
 								  message.data,
-								  NULL,
+								  detail,
 								  NULL,
 								  PLPGSQL_CHECK_WARNING_EXTRA,
 								  0, NULL, NULL);
@@ -379,13 +385,19 @@ plpgsql_check_report_unused_variables(PLpgSQL_checkstate *cstate)
 					PLpgSQL_variable *var = (PLpgSQL_variable *) estate->datums[varno];
 					StringInfoData message;
 
+					const char *fmt = cstate->found_return_dyn_query ?
+							  MAYBE_UNMODIFIED_VARIABLE_TEXT : UNMODIFIED_VARIABLE_TEXT;
+
+					const char *detail = cstate->found_return_dyn_query ?
+							  "cannot to determine result of dynamic SQL" : NULL;
+
 					initStringInfo(&message);
 
-					appendStringInfo(&message, UNMODIFIED_VARIABLE_TEXT, var->refname);
+					appendStringInfo(&message, fmt, var->refname);
 					plpgsql_check_put_error(cstate,
 							  0, 0,
 							  message.data,
-							  NULL,
+							  detail,
 							  NULL,
 							  PLPGSQL_CHECK_WARNING_EXTRA,
 							  0, NULL, NULL);

src/stmtwalk.c

@@ -1956,6 +1956,12 @@ check_dynamic_sql(PLpgSQL_checkstate *cstate,
 										NULL);
 		}
 
+		/* in this case we don't know number of output columns */
+		if (stmt->cmd_type == PLPGSQL_STMT_RETURN_QUERY)
+		{
+			cstate->found_return_dyn_query = true;
+		}
+
 		/*
 		 * In this case, we don't know a result type, and we should
 		 * to raise warning about this situation.