From 841dbe02704e19183c223ec72d2b39d676bd9140 Mon Sep 17 00:00:00 2001
From: Heejong Lee <heejong@gmail.com>
Date: Fri, 22 Nov 2024 01:44:28 -0800
Subject: [PATCH] Support ellipsis in typescript function parameters (#518)

---
 .../semgrep-typescript/common/semgrep-ext.js  | 12 ++++
 .../typescript/corpus/semgrep-ext.txt         | 64 +++++++++++++++++++
 2 files changed, 76 insertions(+)

diff --git a/lang/semgrep-grammars/src/semgrep-typescript/common/semgrep-ext.js b/lang/semgrep-grammars/src/semgrep-typescript/common/semgrep-ext.js
index 9f289042..78b0426d 100644
--- a/lang/semgrep-grammars/src/semgrep-typescript/common/semgrep-ext.js
+++ b/lang/semgrep-grammars/src/semgrep-typescript/common/semgrep-ext.js
@@ -13,6 +13,7 @@ module.exports = {
     [$.semgrep_expression_ellipsis, $.rest_type],
     [$.semgrep_expression_ellipsis, $.rest_type, $.spread_element, $.rest_pattern],
     [$.semgrep_expression_ellipsis, $.spread_element, $.rest_pattern],
+    [$.semgrep_expression_ellipsis, $.semgrep_ellipsis],
   ]),
 
   rules: {
@@ -28,6 +29,16 @@ module.exports = {
     */
 
     semgrep_ellipsis: $ => '...',
+
+    /* ellipsis in function parameters
+     * e.g. function foo(..., x, ...)
+     */
+    _formal_parameter: $ => choice(
+      $.semgrep_ellipsis,
+      $.required_parameter,
+      $.optional_parameter,
+    ),
+
 /* TODO: restore this when the changes are made in semgrep.
    Remove the XXXXXXX when uncommenting.
 
@@ -48,6 +59,7 @@ module.exports = {
       previous,
       $.semgrep_expression_ellipsis,
     ),
+
 /* TODO: restore this when the changes are made in semgrep.
     _jsx_attribute: ($, previous) => choice(
       previous,
diff --git a/lang/semgrep-grammars/src/semgrep-typescript/typescript/corpus/semgrep-ext.txt b/lang/semgrep-grammars/src/semgrep-typescript/typescript/corpus/semgrep-ext.txt
index a08e7d70..5abb4a9b 100644
--- a/lang/semgrep-grammars/src/semgrep-typescript/typescript/corpus/semgrep-ext.txt
+++ b/lang/semgrep-grammars/src/semgrep-typescript/typescript/corpus/semgrep-ext.txt
@@ -52,3 +52,67 @@ case "Foo":
       (string_fragment))
     (expression_statement
       (semgrep_expression_ellipsis))))
+
+==================================
+Ellipsis in function params
+==================================
+
+function foo(...) { ... }
+function foo(..., a) { ... }
+function foo(a, ...) { ... }
+function foo(..., a, ...) { ... }
+function foo(..., @Bar(...) $X, ...) { ... }
+
+---
+
+(program
+  (function_declaration
+    (identifier)
+    (formal_parameters
+      (semgrep_ellipsis))
+    (statement_block
+      (expression_statement
+        (semgrep_expression_ellipsis))))
+  (function_declaration
+    (identifier)
+    (formal_parameters
+      (semgrep_ellipsis)
+      (required_parameter
+        (identifier)))
+    (statement_block
+      (expression_statement
+        (semgrep_expression_ellipsis))))
+  (function_declaration
+    (identifier)
+    (formal_parameters
+      (required_parameter
+        (identifier))
+      (semgrep_ellipsis))
+    (statement_block
+      (expression_statement
+        (semgrep_expression_ellipsis))))
+  (function_declaration
+    (identifier)
+    (formal_parameters
+      (semgrep_ellipsis)
+      (required_parameter
+        (identifier))
+      (semgrep_ellipsis))
+    (statement_block
+      (expression_statement
+        (semgrep_expression_ellipsis))))
+  (function_declaration
+    (identifier)
+    (formal_parameters
+      (semgrep_ellipsis)
+      (required_parameter
+        (decorator
+          (call_expression
+            (identifier)
+            (arguments
+              (semgrep_expression_ellipsis))))
+        (identifier))
+      (semgrep_ellipsis))
+    (statement_block
+      (expression_statement
+        (semgrep_expression_ellipsis)))))