Excluding sourcemaps comment in production builds (#10695)

* Excluding sourcemaps comment in production builds

Fixes MetaMask/metamask-extension#7077

* Fix source map explorer script

The source map explorer script now re-adds the source map comment to
each file to ensure the source map visualization still works. Each
module with a sourcemap is copied to a temporary directory along with
the module it corresponds to, and from there it's passed into
`source-map-explorer`. This should ensure the resulting visualization
matches what it was before.

Everything has been moved inside of functions to generally improve
readability, and to allow the use of local variables.

Co-authored-by: Mark Stacey <markjstacey@gmail.com>

development/build/scripts.js

@@ -254,7 +254,9 @@ function createScriptTasks({ browserPlatforms, livereload }) {
         // note: sourcemaps call arity is important
         buildPipeline.push(sourcemaps.write());
       } else {
-        buildPipeline.push(sourcemaps.write('../sourcemaps'));
+        buildPipeline.push(
+          sourcemaps.write('../sourcemaps', { addComment: false }),
+        );
       }
 
       // write completed bundles

development/source-map-explorer.sh

@@ -5,11 +5,30 @@ set -e
 set -u
 set -o pipefail
 
-mkdir -p build-artifacts/source-map-explorer
-yarn source-map-explorer dist/chrome/inpage.js --html build-artifacts/source-map-explorer/inpage.html
-yarn source-map-explorer dist/chrome/contentscript.js --html build-artifacts/source-map-explorer/contentscript.html
-yarn source-map-explorer dist/chrome/background.js --html build-artifacts/source-map-explorer/background.html
-yarn source-map-explorer dist/chrome/bg-libs.js --html build-artifacts/source-map-explorer/bg-libs.html
-yarn source-map-explorer dist/chrome/ui.js --html build-artifacts/source-map-explorer/ui.html
-yarn source-map-explorer dist/chrome/ui-libs.js --html build-artifacts/source-map-explorer/ui-libs.html
-yarn source-map-explorer dist/chrome/phishing-detect.js --html build-artifacts/source-map-explorer/phishing-detect.html
+function generate_sourcemap() {
+  local temp_dir="${1}"; shift
+  local module_name="${1}"; shift
+
+  cp "dist/chrome/${module_name}.js" "${temp_dir}/"
+  cp "dist/sourcemaps/${module_name}.js.map" "${temp_dir}/"
+  printf '//# sourceMappingURL=%s.js.map' "${module_name}" >> "${temp_dir}/${module_name}.js"
+  yarn source-map-explorer "${temp_dir}/${module_name}.js" "${temp_dir}/${module_name}.js.map" --html "build-artifacts/source-map-explorer/${module_name}.html"
+}
+
+function main() {
+  mkdir -p build-artifacts/source-map-explorer
+
+  local temp_dir
+  temp_dir="$(mktemp -d)"
+
+  for file in dist/sourcemaps/*.js.map; do
+    [[ -e $file ]] || (echo 'Failed to find any JavaScript modules' && exit 1)
+    local filename
+    filename="$(basename "${file}")"
+    local module_name
+    module_name="${filename%.js.map}"
+    generate_sourcemap "${temp_dir}" "${module_name}"
+  done
+}
+
+main