fix: handle invalid hover responses by displaying errors

[ijsnow]

Sometimes language servers return invalid hover information. Currently, codeintellify just sort of gets angry and quits working after this happens. @chrismwendt and I discussed a few different options for handling this and we decided that while the solution this PR has is the ideal solution¹, it is more convenient for consumers of codeintellify.

¹ The ideal solution would be that each language server perfectly adheres to the specification or at least each codeintellify consumer handles the errors on it's own.

[felixfbecker]

Which consumers are we optimising for? Ourselves, or community usage? For the community, it would be nice if we could still highlight that wrong hovers are returned, otherwise these mistakes may never get caught and other clients suffer.

We have code in the webapp that handles more cases than just Python:

https://sourcegraph.sgdev.org/github.com/sourcegraph/sourcegraph/-/blob/web/src/backend/lsp.tsx#L119-141
https://sourcegraph.sgdev.org/github.com/sourcegraph/sourcegraph/-/blob/web/src/backend/lsp.tsx#L173-177

Currently, codeintellify just sort of gets angry and quits working after this happens.

If we adopt the above code (throwing an error if validation fails) it should only show an error hover with "invalid hover returned"

[ijsnow]

This is not optimizing for a subset of consumers. Now when any hover is formatted incorrectly, the error that we map to is displayed.

[codecov]

Codecov Report

Merging #47 into master will increase coverage by <.01%.
The diff coverage is 66.66%.

@@            Coverage Diff             @@
##           master      #47      +/-   ##
==========================================
+ Coverage   65.14%   65.14%   +<.01%     
==========================================
  Files          15       15              
  Lines         634      637       +3     
  Branches      169      172       +3     
==========================================
+ Hits          413      415       +2     
- Misses        221      222       +1

Impacted Files	Coverage Δ
src/hoverifier.ts	56.14% <66.66%> (+0.17%)	⬆️

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[ijsnow]

At my computer now so I can give a more complete response. The fact that there is code to handle this in the web app and not the browser extension is exactly the point of this PR. Additionally, the code linked above would just hide these errors.

The error we map to when !HoverMerged.is(hoverMergedOrNull), is Invalid hover response which is 100% accurate according to the typings at that point. It should either be a valid HoverMerged or null and if its not, we should raise an error, not just correct the shape and pass it on with empty data.

[sourcegraph-bot]

🎉 This PR is included in version 3.7.5 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

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