File models get disposed when contents change on disk

[928PJY]

• VSCode Version:1.8.1
• OS Version:win10

Command "vscode.previewHtml" can only provide two ways to preview a Html resource.
The one is providing Url, but when the Html file changes, how to update the preview content? Is there some sample code?
The second is providing a virtual resource, but when I want to use some js files to render this Html, do I have to give the absolute path? If so, How can I do when js file reference to another js file(in this case, it have to be a relative path(?)).

[928PJY]

I am writing an extension which will preview the DFM, and what I want to preview is a virtual Html resource, this Html will reference to some js files(in relative path), but the VSCode will translate it into absolute path based on the markdown file, I fix this problem by translate the js files's path into absolute path, but when this js files reference to other files, I don't know how to do.Maybe you can provide some advice.

[928PJY]

When I use the first ways to preview Html(provide a Uri), how to trigger the update event.

[jrieken]

When the URI points to a file on disk and that file is inside the current workspace/folder updating happens automatically, when you are showing a virtual resource its content provider must signal changes via an event. Therefore a TextDocumentContentProvider can implement a onDidChange event which in return will be honoured by the editor. There is an example here: https://github.com/Microsoft/vscode-extension-samples/blob/master/previewhtml-sample/src/extension.ts#L20. Full sample: https://github.com/Microsoft/vscode-extension-samples/blob/master/previewhtml-sample/

[928PJY]

There is a small sample, it doesn't behavior as what you said.

[jrieken]

Can you reduce that to something small and simple?

[928PJY]

Yes! Sample is smaller!

[928PJY]

I was writing an extension, which is going to preview DocFx. Extension pass the markdown content to a child process, which will use DocFx engine to render the markdown file into Html, this Html will be written to a temp file, which is the resource of preview page, But When this temp Html changed, Nothing happens to preview page.

[jrieken]

Is this file inside the workspace or did you open the file by itself? Can you open it in source and check if it updates when it is changed on disk?

[928PJY]

The situation is, this file is inside the workspace, but not be opened, and When it is changed by another editor or process, it can't update automatically.

[jrieken]

Thanks for sticking with me. There is actually something wrong. The preview updates as long as the file also open in an editor and stops after that. I need to investigate..

[jrieken]

This happens because the TextFileEditorModelManager decides to dispose the model instead of updating it.

// Dispose models that got changed and are not visible. We do this because otherwise
// cached file models will be stale from the contents on disk.

I don't understand that. There is the IModelService but this comment seems to talk about another cache. My expectation was that the workbench listens on file events, updates models (IModel) that are alive, such that listeners to that can do their work

[928PJY]

Thank you for reopening this issue, I have already solved my problem through another way, but I still want to see this problem can be fixed, thank you!

[bpasero]

Related to #17888

I will revisit this in March given you seem to have a workaround and this is not a recent regression.

Btw we had #5687 open for a while which is the same issue.

[bpasero]

I fixed the fact that we dispose models when file changes so that we now update the model with the new contents. However due to #17888 this is still not working properly but should be once #17888 is done.