From ed69adedcd7140fd93d888d6b9dd46a6153adc7f Mon Sep 17 00:00:00 2001
From: "Alex Lam S.L" <alexlamsl@gmail.com>
Date: Wed, 10 Jun 2020 15:51:00 +0100
Subject: [PATCH] fix corner case in `--reduce-test` (#3985)

---
 test/input/reduce/diff_error.js         |  5 +++++
 test/input/reduce/diff_error.reduced.js | 19 +++++++++++++++++++
 test/mocha/reduce.js                    | 14 ++++++++++++++
 test/reduce.js                          |  3 ++-
 4 files changed, 40 insertions(+), 1 deletion(-)
 create mode 100644 test/input/reduce/diff_error.js
 create mode 100644 test/input/reduce/diff_error.reduced.js

diff --git a/test/input/reduce/diff_error.js b/test/input/reduce/diff_error.js
new file mode 100644
index 00000000..ba267c5c
--- /dev/null
+++ b/test/input/reduce/diff_error.js
@@ -0,0 +1,5 @@
+(function f(a) {
+    do {
+        console.log(f.length);
+    } while (console.log(f += 0));
+})();
diff --git a/test/input/reduce/diff_error.reduced.js b/test/input/reduce/diff_error.reduced.js
new file mode 100644
index 00000000..a76e3d94
--- /dev/null
+++ b/test/input/reduce/diff_error.reduced.js
@@ -0,0 +1,19 @@
+// (beautified)
+(function f(a) {
+    do {
+        console.log(f.length);
+    } while (console.log(f += 0));
+})();
+// output: 1
+// function(){}0
+// 
+// minify: 0
+// function(){}0
+// 
+// options: {
+//   "compress": {
+//     "keep_fargs": false,
+//     "unsafe": true
+//   },
+//   "mangle": false
+// }
\ No newline at end of file
diff --git a/test/mocha/reduce.js b/test/mocha/reduce.js
index 271358be..c1864735 100644
--- a/test/mocha/reduce.js
+++ b/test/mocha/reduce.js
@@ -296,4 +296,18 @@ describe("test/reduce.js", function() {
             "// }",
         ]).join("\n"));
     });
+    it("Should handle corner cases when intermediate case differs only in Error.message", function() {
+        if (semver.satisfies(process.version, "<=0.10")) return;
+        var result = reduce_test(read("test/input/reduce/diff_error.js"), {
+            compress: {
+                keep_fargs: false,
+                unsafe: true,
+            },
+            mangle: false,
+        }, {
+            verbose: false,
+        });
+        if (result.error) throw result.error;
+        assert.strictEqual(result.code, read("test/input/reduce/diff_error.reduced.js"));
+    });
 });
diff --git a/test/reduce.js b/test/reduce.js
index ff2f787c..7f37ea25 100644
--- a/test/reduce.js
+++ b/test/reduce.js
@@ -438,7 +438,8 @@ module.exports = function reduce_test(testcase, minify_options, reduce_options)
                     }
                 }));
                 var code = testcase_ast.print_to_string();
-                if (diff = test_for_diff(code, minify_options, result_cache, max_timeout)) {
+                var diff = test_for_diff(code, minify_options, result_cache, max_timeout);
+                if (diff && !diff.timed_out && !diff.error) {
                     testcase = code;
                     differs = diff;
                 } else {
-- 
2.34.1