Support for custom editors looks completely broken

[pisv]

Is it just me, or support for custom editors looks completely broken on the current master? I mean ordinary custom editors, not just side-by-side diff ones... Can someone please check?

Originally posted by @pisv in #15401

[tsmaeder]

I get a log of 404 messages in the browser log when opening webviews and the webviews fail to load. I'm using the gitlens extension to test and hediet.vscode-drawio. Example logs:

logger-protocol.ts:118 2025-04-07T15:06:50.958Z plugin-host ERROR SyntaxError: "undefined" is not valid JSON
    at JSON.parse (<anonymous>)
    at get localStorage (C:\Users\thomas\.theia-ide\deployedPlugins\hediet.vscode-drawio-1.6.6\extension\dist\extension\index.js:2:128260)
    at C:\Users\thomas\.theia-ide\deployedPlugins\hediet.vscode-drawio-1.6.6\extension\dist\extension\index.js:2:141719
    at Module.lt (C:\Users\thomas\.theia-ide\deployedPlugins\hediet.vscode-drawio-1.6.6\extension\dist\extension\index.js:2:56634)
    at e.DrawioClientFactory.getOfflineHtml (C:\Users\thomas\.theia-ide\deployedPlugins\hediet.vscode-drawio-1.6.6\extension\dist\extension\index.js:2:141702)
    at e.DrawioClientFactory.getHtml (C:\Users\thomas\.theia-ide\deployedPlugins\hediet.vscode-drawio-1.6.6\extension\dist\extension\index.js:2:141444)
    at c.autorun.name (C:\Users\thomas\.theia-ide\deployedPlugins\hediet.vscode-drawio-1.6.6\extension\dist\extension\index.js:2:139389)
    at s (C:\Users\thomas\.theia-ide\deployedPlugins\hediet.vscode-drawio-1.6.6\extension\dist\extension\index.js:2:70258)
    at at (C:\Users\thomas\.theia-ide\deployedPlugins\hediet.vscode-drawio-1.6.6\extension\dist\extension\index.js:2:55963)
    at t.track (C:\Users\thomas\.theia-ide\deployedPlugins\hediet.vscode-drawio-1.6.6\extension\dist\extension\index.js:2:67257)
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main.js:1 
 GET http://bab52053-97fa-4673-bc5c-772b417bd519.webview.localhost:51722/webview…e-drawio-1.6.6/extension/drawio/src/main/webapp/js/croppie/croppie.min.css net::ERR_ABORTED 404 (Not Found)
(anonymous)	@	main.js:1
setTimeout (async)		
(anonymous)	@	main.js:1
main.js:1 
 GET http://bab52053-97fa-4673-bc5c-772b417bd519.webview.localhost:51722/webview…scode-drawio-1.6.6/extension/drawio/src/main/webapp/styles/grapheditor.css net::ERR_ABORTED 404 (Not Found)
main.js:1 
 GET http://bab52053-97fa-4673-bc5c-772b417bd519.webview.localhost:51722/webview…ediet.vscode-drawio-1.6.6/extension/drawio/src/main/webapp/js/PreConfig.js net::ERR_ABORTED 404 (Not Found)
main.js:1 
 GET http://bab52053-97fa-4673-bc5c-772b417bd519.webview.localhost:51722/webview…/hediet.vscode-drawio-1.6.6/extension/drawio/src/main/webapp/js/app.min.js net::ERR_ABORTED 404 (Not Found)
main.js:1 
 GET http://bab52053-97fa-4673-bc5c-772b417bd519.webview.localhost:51722/webview….vscode-drawio-1.6.6/extension/drawio/src/main/webapp/js/extensions.min.js net::ERR_ABORTED 404 (Not Found)
main.js:1 
 GET http://bab52053-97fa-4673-bc5c-772b417bd519.webview.localhost:51722/webview…et.vscode-drawio-1.6.6/extension/drawio/src/main/webapp/js/stencils.min.js net::ERR_ABORTED 404 (Not Found)
main.js:1 
 GET http://bab52053-97fa-4673-bc5c-772b417bd519.webview.localhost:51722/webview…code-drawio-1.6.6/extension/drawio/src/main/webapp/js/shapes-14-6-5.min.js net::ERR_ABORTED 404 (Not Found)
main.js:1 
 GET http://bab52053-97fa-4673-bc5c-772b417bd519.webview.localhost:51722/webview…diet.vscode-drawio-1.6.6/extension/drawio/src/main/webapp/js/PostConfig.js net::ERR_ABORTED 404 (Not Found)
index.html?id=bab520…c5c-772b417bd519:10 Uncaught ReferenceError: Menus is not defined
    at index.html?id=bab520…-772b417bd519:10:13
    at index.html?id=bab520…-772b417bd519:266:6

[tsmaeder]

I quickly searched through recent commits that might be relevant and it seems the the problems stems from this PR (#15331). The commit before works for me and after it doesn't. @colin-grant-work could you chime in whether we can simply revert the change?

[colin-grant-work]

@tsmaeder, we can revert it, but if we do, we should make an issue to fix the problem it identifies, and to add tests to check for whatever regression it caused, since all of our existing tests continued to pass, seemingly.

[pisv]

@tsmaeder Thank you for fixing it so fast! 👍