implement `UGLIFY_BUG_REPORT` (#4516)

4 files changed, 81 insertions, 1 deletions

diff --git a/.github/ISSUE_TEMPLATE/bug_report.md b/.github/ISSUE_TEMPLATE/bug_report.md
index e46005a1..19958945 100644
--- a/.github/ISSUE_TEMPLATE/bug_report.md
+++ b/.github/ISSUE_TEMPLATE/bug_report.md
@@ -31,6 +31,15 @@ test case will be closed.
 
 <!--
 Command-line or API call to UglifyJS without third party tools or libraries.
+
+For users using bundlers or transpilers, you may be able to gather the required
+information through setting the `UGLIFY_BUG_REPORT` environment variable:
+
+    UGLIFY_BUG_REPORT=1         (Linux)
+    set UGLIFY_BUG_REPORT=1     (Windows)
+
+before running your usual build process. The resulting "minified" output should
+contain the necessary details for this report.
 -->
 
 **JavaScript output or error produced.**
diff --git a/bin/uglifyjs b/bin/uglifyjs
index ed01f986..c2576ba0 100755
--- a/bin/uglifyjs
+++ b/bin/uglifyjs
@@ -265,7 +265,7 @@ if (paths.length) {
     process.stdin.on("data", function(chunk) {
         chunks.push(chunk);
     }).on("end", function() {
-        files = [ chunks.join("") ];
+        files = { STDIN: chunks.join("") };
         run();
     });
     process.stdin.resume();
diff --git a/test/mocha/bug-report.js b/test/mocha/bug-report.js
new file mode 100644
index 00000000..480850df
--- /dev/null
+++ b/test/mocha/bug-report.js
@@ -0,0 +1,40 @@
+var assert = require("assert");
+var exec = require("child_process").exec;
+
+describe("UGLIFY_BUG_REPORT", function() {
+    var env = Object.create(process.env);
+    env.UGLIFY_BUG_REPORT = 1;
+    it("Should generate bug report via API", function(done) {
+        exec('"' + process.argv[0] + '"', { env: env }, function(err, stdout) {
+            if (err) throw err;
+            assert.strictEqual(stdout, [
+                "// UGLIFY_BUG_REPORT",
+                "// <<undefined>>",
+                "",
+                "//-------------------------------------------------------------",
+                "// INPUT CODE",
+                "...---...",
+                "",
+            ].join("\n"));
+            done();
+        }).stdin.end('console.log(require("./").minify("...---...").code);');
+    });
+    it("Should generate bug report via CLI", function(done) {
+        exec('"' + process.argv[0] + '" bin/uglifyjs -mc', { env: env }, function(err, stdout) {
+            if (err) throw err;
+            assert.strictEqual(stdout, [
+                "// UGLIFY_BUG_REPORT",
+                "// {",
+                '//   "mangle": {},',
+                '//   "compress": {}',
+                "// }",
+                "",
+                "//-------------------------------------------------------------",
+                "// STDIN",
+                "...---...",
+                "",
+            ].join("\n"));
+            done();
+        }).stdin.end("...---...");
+    });
+});
diff --git a/tools/node.js b/tools/node.js
index 1ebc7730..f1fb28ba 100644
--- a/tools/node.js
+++ b/tools/node.js
@@ -23,6 +23,37 @@ new Function("exports", function() {
     return code.join("\n\n");
 }())(exports);
 
+function to_comment(value) {
+    if (typeof value != "string") value = JSON.stringify(value, function(key, value) {
+        return typeof value == "function" ? "<[ " + value + " ]>" : value;
+    }, 2);
+    return "// " + value.replace(/\n/g, "\n// ");
+}
+
+if (+process.env["UGLIFY_BUG_REPORT"]) exports.minify = function(files, options) {
+    if (typeof options == "undefined") options = "<<undefined>>";
+    var code = [
+        "// UGLIFY_BUG_REPORT",
+        to_comment(options),
+    ];
+    if (typeof files == "string") {
+        code.push("");
+        code.push("//-------------------------------------------------------------")
+        code.push("// INPUT CODE", files);
+    } else for (var name in files) {
+        code.push("");
+        code.push("//-------------------------------------------------------------")
+        code.push(to_comment(name), files[name]);
+    }
+    if (options.sourceMap && options.sourceMap.url) {
+        code.push("");
+        code.push("//# sourceMappingURL=data:application/json;charset=utf-8;base64,eyJ2ZXJzaW9uIjozLCJzb3VyY2VzIjpbXSwibmFtZXMiOltdLCJtYXBwaW5ncyI6IiJ9");
+    }
+    var result = { code: code.join("\n") };
+    if (options.sourceMap) result.map = '{"version":3,"sources":[],"names":[],"mappings":""}';
+    return result;
+};
+
 function describe_ast() {
     var out = OutputStream({ beautify: true });
     function doitem(ctor) {