From c2a3f890b4e1a212290b5e66a3abd3f6acf69fba Mon Sep 17 00:00:00 2001
From: Brandon Wu <49291449+brandonspark@users.noreply.github.com>
Date: Wed, 4 Sep 2024 13:57:25 -0700
Subject: [PATCH] feat(go): basic semgrep support (#504)

* feat: semgrep support for go

* add typed metavars
---
 .../src/semgrep-go/grammar.js                 |  43 +++-
 .../src/semgrep-go/test/corpus/semgrep.txt    | 233 ++++++++++++++++++
 2 files changed, 266 insertions(+), 10 deletions(-)

diff --git a/lang/semgrep-grammars/src/semgrep-go/grammar.js b/lang/semgrep-grammars/src/semgrep-go/grammar.js
index 1c1fc1e4..8bdce890 100644
--- a/lang/semgrep-grammars/src/semgrep-go/grammar.js
+++ b/lang/semgrep-grammars/src/semgrep-go/grammar.js
@@ -17,15 +17,38 @@ module.exports = grammar(base_grammar, {
      if they're not already part of the base grammar.
   */
   rules: {
-  /*
-    semgrep_ellipsis: $ => '...',
-
-    _expression: ($, previous) => {
-      return choice(
-        $.semgrep_ellipsis,
-        ...previous.members
-      );
-    }
-  */
+    semgrep_ellipsis: $ => "...",
+
+    semgrep_ellipsis_metavar : $ => /\$\.\.\.[a-zA-Z_][a-zA-Z_0-9]*/,
+    semgrep_deep_ellipsis: $ => seq("<...", $._expression, "...>"),
+
+    _expression: ($, previous) => choice(
+      previous,
+      $.semgrep_ellipsis_metavar,
+      $.semgrep_deep_ellipsis,
+      $.semgrep_ellipsis,
+      $.typed_metavar
+    ),
+
+    typed_metavar: $ => seq(
+      "(", $.identifier, ":", $._type, ")"
+    ),
+
+    identifier: ($, previous) => token(choice(
+      previous,
+      // inline this here so we can stay inside of the `token`, because
+      // `identifier` is the word token
+      /\$[A-Z_][A-Z_0-9]*/
+    )),
+
+    parameter_declaration: ($, previous) => choice(
+      $.semgrep_ellipsis,
+      $.semgrep_ellipsis_metavar,
+      previous
+    ),
+
+    // slightly more precedence so we bump this up over using `...`
+    // for a semgrep ellipsis
+    implicit_length_array_type: ($, previous) => prec(1, previous)
   }
 });
diff --git a/lang/semgrep-grammars/src/semgrep-go/test/corpus/semgrep.txt b/lang/semgrep-grammars/src/semgrep-go/test/corpus/semgrep.txt
index e69de29b..0a1707ca 100644
--- a/lang/semgrep-grammars/src/semgrep-go/test/corpus/semgrep.txt
+++ b/lang/semgrep-grammars/src/semgrep-go/test/corpus/semgrep.txt
@@ -0,0 +1,233 @@
+================================================================================
+Ellipsis
+================================================================================
+
+...
+
+--------------------------------------------------------------------------------
+
+(source_file
+  (semgrep_ellipsis))
+
+================================================================================
+Top level statements
+================================================================================
+
+x := 1
+...
+y := 2
+
+--------------------------------------------------------------------------------
+
+(source_file
+  (short_var_declaration
+    (expression_list
+      (identifier))
+    (expression_list
+      (int_literal)))
+  (semgrep_ellipsis)
+  (short_var_declaration
+    (expression_list
+      (identifier))
+    (expression_list
+      (int_literal))))
+
+================================================================================
+Function with ellipses
+================================================================================
+
+func $FUNC(x bool, ...) {
+  ...
+}
+
+--------------------------------------------------------------------------------
+
+(source_file
+  (function_declaration
+    (identifier)
+    (parameter_list
+      (parameter_declaration
+        (identifier)
+        (type_identifier))
+      (parameter_declaration
+        (semgrep_ellipsis)))
+    (block
+      (semgrep_ellipsis))))
+
+================================================================================
+Function with ellipses
+================================================================================
+
+func $FUNC(x bool, $...ARGS) {
+  $...BODY
+}
+
+--------------------------------------------------------------------------------
+
+(source_file
+  (function_declaration
+    (identifier)
+    (parameter_list
+      (parameter_declaration
+        (identifier)
+        (type_identifier))
+      (parameter_declaration
+        (semgrep_ellipsis_metavar)))
+    (block
+      (semgrep_ellipsis_metavar))))
+
+================================================================================
+Type declaration with metavariables
+================================================================================
+
+type $TY = $TY2
+
+--------------------------------------------------------------------------------
+
+(source_file
+  (type_declaration
+    (type_alias
+      (type_identifier)
+      (type_identifier))))
+
+================================================================================
+Struct metavariable
+================================================================================
+
+type $STRUCT struct {
+  $FIELD int
+  $FIELD2 $TY
+}
+
+--------------------------------------------------------------------------------
+
+(source_file
+  (type_declaration
+    (type_spec
+      (type_identifier)
+      (struct_type
+        (field_declaration_list
+          (field_declaration
+            (field_identifier)
+            (type_identifier))
+          (field_declaration
+            (field_identifier)
+            (type_identifier)))))))
+
+================================================================================
+Ellipsis args
+================================================================================
+
+foo(..., 5)
+
+--------------------------------------------------------------------------------
+
+(source_file
+  (call_expression
+    (identifier)
+    (argument_list
+      (semgrep_ellipsis)
+      (int_literal))))
+
+================================================================================
+Ellipsis in if
+================================================================================
+
+if (...) {
+  ...
+} else {
+  ...
+}
+
+--------------------------------------------------------------------------------
+
+(source_file
+  (if_statement
+    (parenthesized_expression
+      (semgrep_ellipsis))
+    (block
+      (semgrep_ellipsis))
+    (block
+      (semgrep_ellipsis))))
+
+================================================================================
+Metavariable in import
+================================================================================
+
+import (
+    $NAME "crypto/rand"
+)
+
+--------------------------------------------------------------------------------
+
+(source_file
+  (import_declaration
+    (import_spec_list
+      (import_spec
+        (package_identifier)
+        (interpreted_string_literal)))))
+
+================================================================================
+Deep expression
+================================================================================
+
+<... 1 ...>
+
+--------------------------------------------------------------------------------
+
+(source_file
+  (semgrep_deep_ellipsis
+    (int_literal)))
+
+================================================================================
+Deep expression again
+================================================================================
+
+x := <... foo() ...>
+
+--------------------------------------------------------------------------------
+
+(source_file
+  (short_var_declaration
+    (expression_list
+      (identifier))
+    (expression_list
+      (semgrep_deep_ellipsis
+        (call_expression
+          (identifier)
+          (argument_list))))))
+
+================================================================================
+Typed metavariables
+================================================================================
+
+x := ($TY : bool)
+
+--------------------------------------------------------------------------------
+
+(source_file
+  (short_var_declaration
+    (expression_list
+      (identifier))
+    (expression_list
+      (typed_metavar
+        (identifier)
+        (type_identifier)))))
+
+================================================================================
+Implicit length array type
+================================================================================
+
+x := [...] bool {}
+
+--------------------------------------------------------------------------------
+
+(source_file
+  (short_var_declaration
+    (expression_list
+      (identifier))
+    (expression_list
+      (composite_literal
+        (implicit_length_array_type
+          (type_identifier))
+        (literal_value)))))