Add support for V8 intrinsics via Babel (#6496)

This plugin was recently added on Babel side and allows to parse custom syntax for V8 intrinsics.

They don't clash with any real-world JavaScript syntax, so adding this option should be as safe as any other plugin, and would allow to format JavaScript that uses such intrinsics (e.g. code inside Node.js or V8 itself).

CHANGELOG.unreleased.md

@@ -836,6 +836,29 @@ type C = (number | string)["toString"];
 type D = (keyof T1)["foo"];
 ```
 
+#### JavaScript: Support formatting code with V8 intrinsics. ([#6496] by [@rreverser])
+
+<!-- prettier-ignore -->
+```js
+// Input
+function doSmth()     {
+            %DebugPrint
+        (
+                foo )
+  }
+
+// Prettier (stable)
+SyntaxError: Unexpected token (2:13)
+  1 | function doSmth()     {
+> 2 |             %DebugPrint
+    |             ^
+
+// Prettier (master)
+function doSmth() {
+  %DebugPrint(foo);
+}
+```
+
 [#5910]: https://github.com/prettier/prettier/pull/5910
 [#6033]: https://github.com/prettier/prettier/pull/6033
 [#6186]: https://github.com/prettier/prettier/pull/6186
@@ -863,6 +886,7 @@ type D = (keyof T1)["foo"];
 [#6467]: https://github.com/prettier/prettier/pull/6467
 [#6377]: https://github.com/prettier/prettier/pull/6377
 [#6604]: https://github.com/prettier/prettier/pull/6604
+[#6496]: https://github.com/prettier/prettier/pull/6496
 [@brainkim]: https://github.com/brainkim
 [@duailibe]: https://github.com/duailibe
 [@gavinjoyce]: https://github.com/gavinjoyce
@@ -872,3 +896,4 @@ type D = (keyof T1)["foo"];
 [@bakkot]: https://gibhub.com/bakkot
 [@thorn0]: https://github.com/thorn0
 [@dcyriller]: https://github.com/dcyriller
+[@rreverser]: https://github.com/RReverser

src/language-js/parser-babylon.js

@@ -37,7 +37,8 @@ function babelOptions(extraOptions, extraPlugins) {
         "bigInt",
         "throwExpressions",
         "logicalAssignment",
-        "classPrivateMethods"
+        "classPrivateMethods",
+        "v8intrinsic"
       ].concat(extraPlugins)
     },
     extraOptions

src/language-js/printer-estree.js

@@ -756,6 +756,8 @@ function printPathNoParens(path, options, print, args) {
         printTypeAnnotation(path, options, print)
       ]);
     }
+    case "V8IntrinsicIdentifier":
+      return concat(["%", n.name]);
     case "SpreadElement":
     case "SpreadElementPattern":
     case "RestProperty":

tests/v8_intrinsic/__snapshots__/jsfmt.spec.js.snap

@@ -0,0 +1,47 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`intrinsic_call.js 1`] = `
+====================================options=====================================
+parsers: ["babel"]
+printWidth: 80
+                                                                                | printWidth
+=====================================input======================================
+function doSmth()     {
+            %DebugPrint
+        (
+                foo )
+  }
+
+    function printFunc  (
+        f
+) {
+    if(%
+    IsAsmWasmCode(f))              console.log("asm.js");
+        if(
+
+        % IsWasmCode(
+        f))
+            console.log (
+                "wasm"
+            );
+
+    console.log
+    (%
+        GetFunctioName(f)
+        );
+}
+
+=====================================output=====================================
+function doSmth() {
+  %DebugPrint(foo);
+}
+
+function printFunc(f) {
+  if (%IsAsmWasmCode(f)) console.log("asm.js");
+  if (%IsWasmCode(f)) console.log("wasm");
+
+  console.log(%GetFunctioName(f));
+}
+
+================================================================================
+`;

tests/v8_intrinsic/intrinsic_call.js

@@ -0,0 +1,24 @@
+function doSmth()     {
+            %DebugPrint
+        (
+                foo )
+  }
+
+    function printFunc  (
+        f
+) {
+    if(%
+    IsAsmWasmCode(f))              console.log("asm.js");
+        if(
+
+        % IsWasmCode(
+        f))
+            console.log (
+                "wasm"
+            );
+
+    console.log
+    (%
+        GetFunctioName(f)
+        );
+}

tests/v8_intrinsic/jsfmt.spec.js

@@ -0,0 +1 @@
+run_spec(__dirname, ["babel"]);