From e2a85a1bdb690123fe6f183b43d6509611ab0a97 Mon Sep 17 00:00:00 2001
From: Lukas Taegert-Atkinson <lukastaegert@users.noreply.github.com>
Date: Wed, 27 May 2020 20:17:39 +0200
Subject: [PATCH] Retain pure annotations in class fields (#3599)

* Retain pure annotations in class fields

* Improve coverage

* Only check key if it is computed
---
 src/utils/pureComments.ts                       | 10 ++++++++++
 test/form/samples/pure-class-field/_config.js   |  3 +++
 test/form/samples/pure-class-field/_expected.js |  6 ++++++
 test/form/samples/pure-class-field/main.js      |  4 ++++
 4 files changed, 23 insertions(+)
 create mode 100644 test/form/samples/pure-class-field/_config.js
 create mode 100644 test/form/samples/pure-class-field/_expected.js
 create mode 100644 test/form/samples/pure-class-field/main.js

diff --git a/src/utils/pureComments.ts b/src/utils/pureComments.ts
index 96822746845..c45336a4520 100644
--- a/src/utils/pureComments.ts
+++ b/src/utils/pureComments.ts
@@ -3,6 +3,16 @@ import * as acorn from 'acorn';
 import { base as basicWalker } from 'acorn-walk';
 import { CommentDescription } from '../Module';
 
+// patch up acorn-walk until class-fields are officially supported
+basicWalker.FieldDefinition = function (node: any, st: any, c: any) {
+	if (node.computed) {
+		c(node.key, st, 'Expression');
+	}
+	if (node.value) {
+		c(node.value, st, 'Expression');
+	}
+};
+
 function handlePureAnnotationsOfNode(
 	node: acorn.Node,
 	state: { commentIndex: number; commentNodes: CommentDescription[] },
diff --git a/test/form/samples/pure-class-field/_config.js b/test/form/samples/pure-class-field/_config.js
new file mode 100644
index 00000000000..d2fd9bd5e0a
--- /dev/null
+++ b/test/form/samples/pure-class-field/_config.js
@@ -0,0 +1,3 @@
+module.exports = {
+	description: 'retains pure annotations in class fields'
+};
diff --git a/test/form/samples/pure-class-field/_expected.js b/test/form/samples/pure-class-field/_expected.js
new file mode 100644
index 00000000000..b03c81c0cd0
--- /dev/null
+++ b/test/form/samples/pure-class-field/_expected.js
@@ -0,0 +1,6 @@
+class main {
+	static k = /*#__PURE__*/ V();
+	static [/*#__PURE__*/ W()];
+}
+
+export default main;
diff --git a/test/form/samples/pure-class-field/main.js b/test/form/samples/pure-class-field/main.js
new file mode 100644
index 00000000000..bc05c5307b5
--- /dev/null
+++ b/test/form/samples/pure-class-field/main.js
@@ -0,0 +1,4 @@
+export default class {
+	static k = /*#__PURE__*/ V();
+	static [/*#__PURE__*/ W()];
+}