do not add source map comments by default

[maxwell8888]

Generating source maps is turned off by default according to the docs, however npx snowpack install will still add source map comment lines like:

//# sourceMappingURL=index.js.map

This causes browsers to log warnings when they try and fetch source maps that don't exist.

[maxwell8888]

Also npx snowpack dev seems also also be generating files with source map comments behind the scenes because a lot of 404 errors for missing source maps are being logged to the console.

[drwpow]

Interesting. Yes that’s definitely not expected behavior by default. Can you confirm which files those are in? I am seeing that if source map URLs are already present in the npm packages (lit-element is an example of this), Snowpack doesn’t actively remove those (maybe it should?). But it shouldn’t be actively generating those in your source code.

[FredKSchott]

This actually might be a Rollup regression? I know that we used to strip these automatically as a part of installing (and it wasn't code that I wrote that did it).

[maxwell8888]

Ah, yes it seems to just be for firebase and lit-html, so yeah snowpack is not doing it, sorry. Below is all the 404s getting logged.

[snowpack] [404] /favicon.ico
  ✘ /Users/max/projects/snowpack-no-firebase-server/src/favicon.ico
[snowpack] [404] /web_modules/firebase/index.esm.js.map
  ✘ /Users/max/projects/snowpack-no-firebase-server/node_modules/.cache/snowpack/dev/firebase/index.esm.js
  ✘ /Users/max/projects/snowpack-no-firebase-server/src/web_modules/firebase/index.esm.js
  ✘ /Users/max/projects/snowpack-no-firebase-server/src/web_modules/firebase/index.esm.mjs
  ✘ /Users/max/projects/snowpack-no-firebase-server/src/web_modules/firebase/index.esm.jsx
  ✘ /Users/max/projects/snowpack-no-firebase-server/src/web_modules/firebase/index.esm.ts
  ✘ /Users/max/projects/snowpack-no-firebase-server/src/web_modules/firebase/index.esm.tsx
[snowpack] [404] /web_modules/updating-element.js.map
  ✘ /Users/max/projects/snowpack-no-firebase-server/node_modules/.cache/snowpack/dev/updating-element.js
  ✘ /Users/max/projects/snowpack-no-firebase-server/src/web_modules/updating-element.js
  ✘ /Users/max/projects/snowpack-no-firebase-server/src/web_modules/updating-element.mjs
  ✘ /Users/max/projects/snowpack-no-firebase-server/src/web_modules/updating-element.jsx
  ✘ /Users/max/projects/snowpack-no-firebase-server/src/web_modules/updating-element.ts
  ✘ /Users/max/projects/snowpack-no-firebase-server/src/web_modules/updating-element.tsx
[snowpack] [404] /web_modules/common/lit-html.js.map
  ✘ /Users/max/projects/snowpack-no-firebase-server/node_modules/.cache/snowpack/dev/common/lit-html.js
  ✘ /Users/max/projects/snowpack-no-firebase-server/src/web_modules/common/lit-html.js
  ✘ /Users/max/projects/snowpack-no-firebase-server/src/web_modules/common/lit-html.mjs
  ✘ /Users/max/projects/snowpack-no-firebase-server/src/web_modules/common/lit-html.jsx
  ✘ /Users/max/projects/snowpack-no-firebase-server/src/web_modules/common/lit-html.ts
  ✘ /Users/max/projects/snowpack-no-firebase-server/src/web_modules/common/lit-html.tsx
[snowpack] [404] /web_modules/common/index.esm.js.map
  ✘ /Users/max/projects/snowpack-no-firebase-server/node_modules/.cache/snowpack/dev/common/index.esm.js
  ✘ /Users/max/projects/snowpack-no-firebase-server/src/web_modules/common/index.esm.js
  ✘ /Users/max/projects/snowpack-no-firebase-server/src/web_modules/common/index.esm.mjs
  ✘ /Users/max/projects/snowpack-no-firebase-server/src/web_modules/common/index.esm.jsx
  ✘ /Users/max/projects/snowpack-no-firebase-server/src/web_modules/common/index.esm.ts
  ✘ /Users/max/projects/snowpack-no-firebase-server/src/web_modules/common/index.esm.tsx
[snowpack] [404] /web_modules/common/foundation.js.map
  ✘ /Users/max/projects/snowpack-no-firebase-server/node_modules/.cache/snowpack/dev/common/foundation.js
  ✘ /Users/max/projects/snowpack-no-firebase-server/src/web_modules/common/foundation.js
  ✘ /Users/max/projects/snowpack-no-firebase-server/src/web_modules/common/foundation.mjs
  ✘ /Users/max/projects/snowpack-no-firebase-server/src/web_modules/common/foundation.jsx
  ✘ /Users/max/projects/snowpack-no-firebase-server/src/web_modules/common/foundation.ts
  ✘ /Users/max/projects/snowpack-no-firebase-server/src/web_modules/common/foundation.tsx
[snowpack] [404] /web_modules/common/index.esm.js.map
  ✘ /Users/max/projects/snowpack-no-firebase-server/node_modules/.cache/snowpack/dev/common/index.esm.js
  ✘ /Users/max/projects/snowpack-no-firebase-server/src/web_modules/common/index.esm.js
  ✘ /Users/max/projects/snowpack-no-firebase-server/src/web_modules/common/index.esm.mjs
  ✘ /Users/max/projects/snowpack-no-firebase-server/src/web_modules/common/index.esm.jsx
  ✘ /Users/max/projects/snowpack-no-firebase-server/src/web_modules/common/index.esm.ts
  ✘ /Users/max/projects/snowpack-no-firebase-server/src/web_modules/common/index.esm.tsx

[maxwell8888]

As a quick fix, I was planning on avoiding these errors by enabling source maps for npx snowpack dev but as far as I can make out in the docs, there is no option for this?

[FredKSchott]

there is installOptions.sourceMap https://www.snowpack.dev/#install-options

[drwpow]

Or you can pass the --source-maps CLI flag to any command

[maxwell8888]

I have the following snowpack.config.json and I'm still getting 404s for missing source maps after running npx snowpack dev.

{
  "mount": {
    "src": "/"
  },
  "plugins": [],
  "installOptions": { "sourceMap": true }
}

[FredKSchott]

Okay, then I think this is a regression and maybe as a part of the Rollup version bump we did a couple of releases ago. Maybe not.

Regardless, sourcemap comments are easy to strip ourselves, and we'll have a bit more confidence in it. Prioritized here: #932

@maxwell8888 if you have any interest in playing around with a fix, we'd love the help!