1 files changed, 61 insertions, 0 deletions
diff --git a/devtools/client/debugger/src/utils/isMinified.js b/devtools/client/debugger/src/utils/isMinified.js
new file mode 100644
index 0000000000..1a80bdea6a
--- /dev/null
+++ b/devtools/client/debugger/src/utils/isMinified.js
@@ -0,0 +1,61 @@
+/* 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/>. */
+
+// @flow
+
+import type { SourceWithContent } from "../types";
+import { isFulfilled } from "./async-value";
+
+// Used to detect minification for automatic pretty printing
+const SAMPLE_SIZE = 50;
+const INDENT_COUNT_THRESHOLD = 5;
+const CHARACTER_LIMIT = 250;
+const _minifiedCache = new Map();
+
+export function isMinified(source: SourceWithContent) {
+  if (_minifiedCache.has(source.id)) {
+    return _minifiedCache.get(source.id);
+  }
+
+  if (
+    !source.content ||
+    !isFulfilled(source.content) ||
+    source.content.value.type !== "text"
+  ) {
+    return false;
+  }
+
+  let text = source.content.value.value;
+
+  let lineEndIndex = 0;
+  let lineStartIndex = 0;
+  let lines = 0;
+  let indentCount = 0;
+  let overCharLimit = false;
+
+  // Strip comments.
+  text = text.replace(/\/\*[\S\s]*?\*\/|\/\/(.+|\n)/g, "");
+
+  while (lines++ < SAMPLE_SIZE) {
+    lineEndIndex = text.indexOf("\n", lineStartIndex);
+    if (lineEndIndex == -1) {
+      break;
+    }
+    if (/^\s+/.test(text.slice(lineStartIndex, lineEndIndex))) {
+      indentCount++;
+    }
+    // For files with no indents but are not minified.
+    if (lineEndIndex - lineStartIndex > CHARACTER_LIMIT) {
+      overCharLimit = true;
+      break;
+    }
+    lineStartIndex = lineEndIndex + 1;
+  }
+
+  const minified =
+    (indentCount / lines) * 100 < INDENT_COUNT_THRESHOLD || overCharLimit;
+
+  _minifiedCache.set(source.id, minified);
+  return minified;
+}