3 files changed, 76 insertions, 0 deletions
diff --git a/devtools/client/debugger/src/workers/pretty-print/index.js b/devtools/client/debugger/src/workers/pretty-print/index.js
new file mode 100644
index 0000000000..78ed2ab4fc
--- /dev/null
+++ b/devtools/client/debugger/src/workers/pretty-print/index.js
@@ -0,0 +1,25 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at <http://mozilla.org/MPL/2.0/>. */
+
+import { prefs } from "../../utils/prefs";
+import { WorkerDispatcher } from "devtools/client/shared/worker-utils";
+
+const WORKER_URL =
+  "resource://devtools/client/debugger/dist/pretty-print-worker.js";
+
+export class PrettyPrintDispatcher extends WorkerDispatcher {
+  constructor(jestUrl) {
+    super(jestUrl || WORKER_URL);
+  }
+
+  #prettyPrintTask = this.task("prettyPrint");
+
+  prettyPrint({ url, text }) {
+    return this.#prettyPrintTask({
+      url,
+      indent: prefs.indentSize,
+      sourceText: text,
+    });
+  }
+}
diff --git a/devtools/client/debugger/src/workers/pretty-print/moz.build b/devtools/client/debugger/src/workers/pretty-print/moz.build
new file mode 100644
index 0000000000..b7223ac81a
--- /dev/null
+++ b/devtools/client/debugger/src/workers/pretty-print/moz.build
@@ -0,0 +1,10 @@
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+DIRS += []
+
+CompiledModules(
+    "index.js",
+)
diff --git a/devtools/client/debugger/src/workers/pretty-print/worker.js b/devtools/client/debugger/src/workers/pretty-print/worker.js
new file mode 100644
index 0000000000..299da0b1c4
--- /dev/null
+++ b/devtools/client/debugger/src/workers/pretty-print/worker.js
@@ -0,0 +1,41 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at <http://mozilla.org/MPL/2.0/>. */
+
+import prettyFast from "pretty-fast";
+
+import { workerHandler } from "devtools/client/shared/worker-utils";
+
+function prettyPrint({ url, indent, sourceText }) {
+  const prettified = prettyFast(sourceText, {
+    url,
+    indent: " ".repeat(indent),
+  });
+
+  return {
+    code: prettified.code,
+    mappings: invertMappings(prettified.map._mappings),
+  };
+}
+
+function invertMappings(mappings) {
+  return mappings._array.map(m => {
+    const mapping = {
+      generated: {
+        line: m.originalLine,
+        column: m.originalColumn,
+      },
+    };
+    if (m.source) {
+      mapping.source = m.source;
+      mapping.original = {
+        line: m.generatedLine,
+        column: m.generatedColumn,
+      };
+      mapping.name = m.name;
+    }
+    return mapping;
+  });
+}
+
+self.onmessage = workerHandler({ prettyPrint });