Could you please tell me more about your setup, since I cannot repro locally?

As far as I understand:
- main.js is served from localhost;
- it points to main.js.map served from localhost;
- source map includes main.ts served from localhost;
- part of the sources including main.ts is in workspaces;
- main.ts shows up blank.

If something is different (e.g. file:/// url vs localhost, main.js.map or main.ts being in different places, anything else) - please tell.

@flo: could you please also open devtools-on-devtools (like described here: https://coderwall.com/p/0m4hqa/chrome-devtools-inception) and check if there are any errors?

Maybe I've chosen a too simplistic example.
Let's do it in more detail:

I have the following files in my workspace:
module1.ts
module2.ts

They are transpiled and concatenated into main.js (a sourcemap is available as main.js.map).

main.js & main.js.map are served to the client.
module1.ts & module2.ts are not available for the application server.

I disabled all Chrome-extensions.
In my Chrome-devtools I've configured the workspace to link to my dev-folder.
Furthermore main.js on the app-server is mapped to main.js in my workspace.

The workspace-folder contains:
module1.ts
module2.ts
main.js
main.js.map

How to reproduce:
1) Within Chrome-devtools I create a breakpoint in main.js.
2) Chrome opens a new source-tab with the title module1.ts, but it is empty. It shows a gray "1" as the only line-number and it seems that this file is empty.
3) If I hover over the source-tab it shows file://C:/path/to/my/workspace/module1.ts
4) The console of the devtools-on-devtools tell me that it tries to open module1.ts at http://localhost (HTTP status code:404).

Further explorations:
5) If the app breaks at the breakpoint it presents an empty file "module1.ts".
6) If I open module1.ts in an editor the DevTools recognize the file-change and the correct file content is presented.
7) If I reload the page the file-content is gone again (empty file).
8) If I copy module1.ts to the app-server-directory the devtools work as expected -> correct file content is shown.

Thank you for detailed report! There seems to be a race between establishing workspace mapping and loading content, which sometimes leads to empty content.

So far I haven't managed to reproduce, but we are working on a potential fix.

I think I'm hitting this, as well. Let me know if I can help provide more details.

Everyone affected: could you please check if Chrome Canary has this issue as well?

I just updated to Chrome 56 and it does not appear to fix the issue for me. The files still open as empty.

@Dan: Any chance you can check Chrome Canary?

@lushnikov: Just installed Canary, and it seems to be loading the files properly.

Tried with Canary: Work like a charm! Thx!

 Issue 696843  has been merged into this issue.

 Issue 696841  has been merged into this issue.