Correct identification of uri scheme according to rfc3986

[vzhukovs]

What it does

This changes proposal fix identification of uri scheme. The problem is in regular expression, that matches uri scheme, it is trying to find scheme according to pattern \w+ which matches any word character (alphanumeric and underscore).

According to https://tools.ietf.org/html/rfc3986#section-3.1 underscore cannot be used as part of uri scheme:

Scheme names consist of a sequence of characters beginning with a
letter and followed by any combination of letters, digits, plus
("+"), period ("."), or hyphen ("-").

Proposed changes is to align matching to rfc specification and use regular expression: /^\/([a-zA-Z0-9.\-+]+)\/(.+)$/ instead of /^\/(\w+)\/(.+)$/.

This might be helpful for extensions, that provides custom resource scheme instead of vscode-resource://. Especially when extension that provides webview is located in different container/user machine and content to the remote resource is given by provided scheme.

Signed-off-by: Vladyslav Zhukovskyi vzhukovs@redhat.com

How to test

To check this Theia has to be run in multi-container environment, like OpenShift: create and run workspace.
This workspace configuration also provides an extension that runs in dedicate container: redhat.vscode-didact.
After workspace start try to open any sample didact tutorial, resources from this webview (js, css) will be loaded using different uri scheme and webview will be displayed the same way as it runs locally on single node environment.

Review checklist

• as an author, I have thoroughly tested my changes and carefully followed the review guidelines

Reminder for reviewers

• as a reviewer, I agree to behave in accordance with the review guidelines

[paul-marechal]

Looks good to me, can you just post an example of URI that used to trigger the old regex when it should have not?

[vzhukovs]

Hi @marechal-p, sure, sorry for late response.

Here is the flow how to test this PR:

• Clone vzhukovs/vscode-webview-sample repository or download already built VS Code extension sample-0.0.1.vsix
• Locate result vsix file in /plugins directory
• Run command MemFS: Show Webview

How does it work in VS Code:

How does it work from current PR:

How does it work from master branch:

Sample extension provides two subjects:

• Sample In Memory File System Provider with scheme file-sidecar-memfs:/. This File System Provider already contains the file called styles.css with css content. It can be accessed by URI: file-sidecar-memfs:/styles.css. This file is included into webview html content.
• Sample webview with included above styles.

When we change file scheme from file-sidecar-memfs:/ to file_sidecar_memfs:/ which is wrong according to RFC specification, we'll get the following behavior, which now works in master branch:

Example of VS Code:

Example of Theia from current PR:

Example of Theia from master branch:

[vince-fugnitto]

@vzhukovs I verified the changes given the example plugin and it worked correctly 👍

---

I verified that:

master: incorrectly displays the codicon webview:

pull-request: the codicon webview is correctly displayed, like vscode: