From d35b92cff6c8a6c5cd8acd21bacfd0193e13c6ba Mon Sep 17 00:00:00 2001
From: kzc <zaxxon2011@gmail.com>
Date: Mon, 20 Feb 2017 21:49:47 -0500
Subject: [PATCH] remove [#@]__PURE__ hint from comment when pure call dropped

---
 lib/compress.js             | 15 ++++++++++-----
 test/compress/issue-1261.js |  9 +++++++++
 test/mocha/minify.js        | 15 +++++++++++++++
 3 files changed, 34 insertions(+), 5 deletions(-)

diff --git a/lib/compress.js b/lib/compress.js
index 0c6e4c31..5e4c483a 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -1273,21 +1273,26 @@ merge(Compressor.prototype, {
         def(AST_Constant, return_false);
         def(AST_This, return_false);
 
-        var pure_regex = /[@#]__PURE__/;
+        var pure_regex = /[@#]__PURE__/g;
         function has_pure_annotation(node) {
             if (node.pure !== undefined) return node.pure;
             var pure = false;
+            var comments, last_comment;
             if (node.start
-                && node.start.comments_before
-                && node.start.comments_before.length
-                && pure_regex.test(node.start.comments_before[node.start.comments_before.length - 1].value)) {
+                && (comments = node.start.comments_before)
+                && comments.length
+                && pure_regex.test((last_comment = comments[comments.length - 1]).value)) {
+                last_comment.value = last_comment.value.replace(pure_regex, ' ');
                 pure = true;
             }
             return node.pure = pure;
         }
 
         def(AST_Call, function(compressor){
-            if (has_pure_annotation(this)) return false;
+            if (has_pure_annotation(this)) {
+                compressor.warn("Dropping __PURE__ call [{file}:{line},{col}]", this.start);
+                return false;
+            }
             var pure = compressor.option("pure_funcs");
             if (!pure) return true;
             if (typeof pure == "function") return pure(this);
diff --git a/test/compress/issue-1261.js b/test/compress/issue-1261.js
index beb00949..eedf4d4f 100644
--- a/test/compress/issue-1261.js
+++ b/test/compress/issue-1261.js
@@ -48,4 +48,13 @@ pure_function_calls: {
         baz(), quux();
         a.b(), f.g();
     }
+    expect_warnings: [
+        "WARN: Dropping __PURE__ call [test/compress/issue-1261.js:17,8]",
+        "WARN: Dropping side-effect-free statement [test/compress/issue-1261.js:17,8]",
+        "WARN: Dropping __PURE__ call [test/compress/issue-1261.js:30,37]",
+        "WARN: Dropping unused variable iife2 [test/compress/issue-1261.js:30,16]",
+        "WARN: Dropping side-effect-free statement [test/compress/issue-1261.js:28,8]",
+        "WARN: Dropping __PURE__ call [test/compress/issue-1261.js:38,8]",
+        "WARN: Dropping __PURE__ call [test/compress/issue-1261.js:39,31]"
+    ]
 }
diff --git a/test/mocha/minify.js b/test/mocha/minify.js
index 70cf73ae..8fe1565f 100644
--- a/test/mocha/minify.js
+++ b/test/mocha/minify.js
@@ -95,4 +95,19 @@ describe("minify", function() {
             assert.strictEqual(code, "var a=function(n){return n};");
         });
     });
+
+    describe("#__PURE__", function() {
+        it("should drop #__PURE__ hint after use", function() {
+            var result = Uglify.minify('//@__PURE__ comment1 #__PURE__ comment2\n foo(), bar();', {
+                fromString: true,
+                output: {
+                    comments: "all",
+                    beautify: false,
+                }
+            });
+            var code = result.code;
+            assert.strictEqual(code, "//  comment1   comment2\nbar();");
+        });
+    });
+
 });