The Nim stdlib JSON modules parse JSON in a lenient way: they silently ignore: - a comma after the last item in an array or object - a line comment with `//` - a potentially-multi-line comment with `/* */` This is useful for parsing real-world JSON, but is bad for our use case of validating JSON. JSON that contains a trailing comma or such comments is technically invalid [1], and less portable. Most JSON parsers produce an error for a trailing comma, including the Ruby library that Exercism uses. Therefore `configlet lint` should produce an error for a trailing comma, so that a track doesn't merge a PR that contains one. This commit adds our own copies of the Nim JSON modules to our repo, and patches them to raise an exception for these cases. Each module was copied from the latest version on Nim's `version-1-4` branch. In the future, we will pull in upstream changes to these files when we update the Nim version. This approach is better than calling something like `jq` because it: - doesn't require/prefer the user to have an extra program installed - doesn't special-case running in CI - doesn't require refactoring our codebase - is much faster We use the somewhat-obscure `nimscript.patchFile` [2] mechanism to override the location of the `json` and `parsejson` modules, so that we can keep `std/json` in our import statements. Instead of the `patchFile` approach, it would also be possible to apply some transformation to the AST of the relevant procs at compile-time, but that's less readable and harder to maintain. Our approach might be obsoleted in the future - for example, if we ever move to some other JSON library, or if the upstream `parseJson` gains e.g. an `allowTrailingCommas = true` argument. [1] See e.g. https://www.json.org/json-en.html [2] https://nim-lang.org/docs/nimscript.html#patchFile%2Cstring%2Cstring%2Cstring Closes: #345 See also: #312

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lint: should exit non-zero for trailing commas and comments with // and /* */ #345

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lint: should exit non-zero for trailing commas and comments with `//` and `/* */` #345