Validate CodeMirror as alternative blob view implementation

[fkling]

This issues keeps track of the work that needs to be done for a baseline implementation of the blob view with CodeMirror.

The feature flag is enableCodeMirrorFileView.

• Add minimal implementation behind feature flag Blob: add feature flag for new CodeMirror implementation #37922
  • Sync line selection to/from URL
• Enable syntax highlighting with SCIP data
  • POC: Syntax highlighting for CodeMirror based blob view #39116
  • Client side: blob: Syntax highlighting for CodeMirror blob view #39386
  • Syntax highlight server emit SCIP from syntect #39264
  • Syntax highlight server #2 https://github.com/sourcegraph/sourcegraph/pull/39850
  • GraphQL/Go glue https://github.com/sourcegraph/sourcegraph/pull/40166
• Code intel popovers
  • https://github.com/sourcegraph/sourcegraph/pull/39482
  • https://github.com/sourcegraph/sourcegraph/pull/39650
  • https://github.com/sourcegraph/sourcegraph/pull/39881
• Search with meta+F https://github.com/sourcegraph/sourcegraph/pull/39884
• Basic telemetry
• Jump to definition
  • https://github.com/sourcegraph/sourcegraph/pull/39881
• Click to jump to definition
  • From @fkling: As long as we have a real text cursor it would be surprising if we implemented this exact behavior. Apparently IDEs support this if a modifier key is pressed, so we should consider to do the same.
  • Implementation without modifier: https://github.com/sourcegraph/sourcegraph/pull/40232
• Find references
  • https://github.com/sourcegraph/sourcegraph/pull/39881
• Git blame
  • https://github.com/sourcegraph/sourcegraph/pull/39650
• Highlight symbol references on hover
  • https://github.com/sourcegraph/sourcegraph/pull/39482
  • https://github.com/sourcegraph/sourcegraph/pull/39650
• Support status bar (including extensions)
  • https://github.com/sourcegraph/sourcegraph/pull/39650
• Support extension API as far as possible and document what isn't supported (if any)
  • https://github.com/sourcegraph/sourcegraph/pull/39650

Known issues to be fixed/discussed:

• Selected line is not synced with cursor position and therefore not sent to extensions
  • Handled in https://github.com/sourcegraph/sourcegraph/pull/40131 by sending the information about selected lines to the extensions instead.
• File content is visible under line numbers (looks like line number background is transparent?)
  • https://github.com/sourcegraph/sourcegraph/pull/40131
• Dismissing the hovercard info box causes the hovercard to shrink upwards, "detaching" it from the line/token it was shown for.
  • We either need to call CodeMirror's repositioning logic
    • this was also done in https://github.com/sourcegraph/sourcegraph/pull/39881
  • Or change the style so that the the dimensions of the hovercard don't change.
• Hovercards are disabled in reference panel blob view (see https://github.com/sourcegraph/sourcegraph/pull/40131 for more information)
  • From @fkling: Issue was something different. See PR If replacing <Router /> with <MemoryRouter /> would fix the navigation issue (which I don't know), then we could introduce a special flag/config option to instruct the React wrapper to use MemoryRouter instead of Router. It's not pretty but doable. But if simply using <MemoryRouter /> would not solve the issue then I don't think there is anything we can do about that (except refactoring the ref panel and hover cards to work differently).
    So whether or not to fix/change this is up for debate.
  • https://github.com/sourcegraph/sourcegraph/pull/40249
• Close button is not functional in un-pinned hovercards
  • From @fkling: Planned solution, as discussed below: Hide close button if hovercard is not pinned
  • Hide close button: https://github.com/sourcegraph/sourcegraph/pull/40232

[macraig]

Small bug: Popover close button doesn't seem to work

CleanShot.2022-08-08.at.12.59.39.mp4

[fkling]

@macraig

Small bug: Popover close button doesn't seem to work

I can make that work somehow, but do we even need the x if the hovercard isn't pinned? Just moving the cursor anywhere else (outside the hovercard) will hide it.

[macraig]

@fkling not really, we should remove if when it isn't pinned then?

[fkling]

@macraig That would make more sense to me.

[olafurpg]

Closing this as "successfully validated". We are not going to ship this with 4.0 since there are still a few remaining issues that we'd like to fix before enabling the new blob view by default. The remaining issues are tracked in the Code Navigation tab of our project board https://github.com/orgs/sourcegraph/projects/211/views/21