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The URI standard RFC 3986 is ambiguous about whether percent encoding and their represented characters are considered equivalent. VS Code considers them equivalent and treats them the same:
```js
vscode.Uri.parse("x://a?b=xxxx%3Dyyyy").toString() -> 'x://a?b%3Dxxxx%3Dyyyy'
vscode.Uri.parse("x://a?b=xxxx%3Dyyyy").toString(/*skipEncoding=*/true) -> 'x://a?b=xxxx=yyyy'
```
This causes issues because SourceKit-LSP's macro expansion URLs encoded by URLComponents use `=` do denote the separation of a key and a value in the outer query. The value of the `parent` key may itself contain query items, which use the escaped form '%3D'. Simplified, such a URL may look like `scheme://host?parent=scheme://host?line%3D2`.
But after running this through VS Code's URI type `=` and `%3D` get canonicalized and are indistinguishable.
To avoid this ambiguity, always percent escape the characters we use to distinguish URL query parameters, producing the following URL: `scheme://host?parent%3Dscheme://host%3Fline%253D2`.