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Proposal for enhancing ways to extend tsconfig file #56436
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I would definitely like to see more powerful options like these here. A few thoughts:
For
mergefunctionality, I like the syntax that Tailwind uses for distinguishing between overrides and extensions:{ "extends": "./tsconfig.base.json", "compilerOptions": { // Override: "paths": { "@libs/*": ["libs/*"], "@project1/*": ["project1/*"] }, // Merge: "extend": { "paths": { "@libs/*": ["libs/*"], "@project1/*": ["project1/*"] } } } }
I think the semantics can be the same as what you proposed, but (a) this scheme has prior art that will be familiar to many, and (b) the indicator that an extension is happening is more closely colocated with the property doing the extending.
Instead of
raw, I think I prefer the use of interpolated variables, which I think have come up in some discussions in the past:// tsconfig.base.json { "compilerOptions": { "outDir": "${projectRoot}/dist" } }
This is again just different syntax for the same semantics you proposed, but I like it because (a) it’s obvious what’s intended to happen just by looking at the option value, (b) it’s impossible to forget whether
"raw"belongs in the extending or base config, and (c) the word “raw” doesn’t do as much for my intuition about what’s going to happen as seeing a variable placeholder (the name of which is debatable).Reacted by Gabriele Tomberli, Ethan Diamond and GuilhermeErmelFor
mergei thought about having separate entry because ofreferenceswhich many people want to extend and is not part ofcompilerOptionsand is array of objects and not object itself.For
rawusing syntax while more clear${projectRoot}/dist, it means that we have to do file path parsing on each config instead of relying on one property to do "transform" to either absolute path or use raw one.Reacted by Konstantin Tieber, Danny França and AramI find the desire to extend
referencespretty suspicious, but I thinkextendcovers that well since it could appear both insidecompilerOptionsand at the root:{ "compilerOptions": { "extend": { "paths": { "@/foo/*": ["../packages/foo/dist/*"] } } }, "extend": { "references": [ { "path": "../packages/foo" } ] } }
Overall, I think clarity should be the top priority—it’s hard to imagine config parsing being a significant part of the total compilation time of a large app.
we probably need to use "merge" instead of "extend" given we already have "extends" at root
Reacted by Aram, Danny França and Lennert SoffersReacted by Danny FrançaReacted by Danny FrançaWriting
extendunder other options doesn't provide much clarity and conciseness. But I agree that extending references does not sound great.The original
mergeproperty proposal looks fantastic. It seems natural for an object to be merged and an array to be concatenated.The raw option, as described, also seems fantastic. It gives projects control over paths and allows them to keep standards easily.
Regarding
mergeandrawconfigs on the base config, I think options should be ignored entirely if the tsconfig does not extend another. ButrawExtendlooks like a great way of establishing those standards for path-like properties.Making the merge too configurable seems too much. A simple object merge and array concat seem reasonable and beautifully address most users' requests.
Thanks a lot for bringing that to light, Sheetal Nandi (@sheetalkamat); I hope other users engage in this discussion.
Reacted by Aram+1 A very useful and necessary feature, especially in monorepositories (as in my case)
Coincidentally, we are developing a system that requires processing of this kind of configs with a declarative extras (
preset,extends), so on, etc. In short, the workaround for the mentioned case looks like this:const tsconfig = await populate('tsconfig.json', { rules: { compilerOptions: 'merge', 'compilerOptions.paths': 'merge', 'compilerOptions.typeRoots': 'merge' }, vmap({value, cwd, root, prefix, key}) { if (cwd !== root && ( prefix === 'compilerOptions.outDir' || prefix.startsWith('compilerOptions.typeRoots.') || /^compilerOptions\.paths\.[^.]+\./.test(prefix)) ) { return path.join(path.relative(root, cwd), value) } return value } })
It's definitely too verbose. So
we're planning to use this proposal syntax insteadwe've added support for the shorthand syntax instead:const tsconfig = await populate('tsconfig.json', { compilerOptions: 'merge', 'compilerOptions.paths': 'merge', 'compilerOptions.typeRoots': 'merge', 'compilerOptions.typeRoots.*': 'rebase', 'compilerOptions.outDir': 'rebase', 'compilerOptions.paths.*.*': 'rebase' })
Reacted by Ryan Cavanaugh and Danny França
🔍 Search Terms
"extends", "merge", "compilerOptions", "paths", "outdir", "include", "exclude", "typeRoots", "references", "tsconfig", "ability to merge tsconfig", "ability to make tsconfig paths relative to final config"
✅ Viability Checklist
⭐ Suggestion
Today when you extend a config the options written in the final config override the options from the base config. Here is sample of what happens today:
Here is what it would mean that project1 tsconfig was written as:
Over years users have asked us for ability to create a final config that adds to base config instead of overriding. This is extremely useful for
pathsfrom compiler options or sayreferencesthat specify project references.This would allow to users to write a base config that contains common options that shouldn't have to be copied in all projects and yet allowing projects to specify there additional specific options.
For example in above sample, one would expect a way to write config such that final
pathsproperty is:Here is the proposal to add
mergeas root level config property that specifies options that need to merged instead of completely overwritten in the final config.The values specified in merge can be root level properties:
files,include,excludeandreferencesor option names from eithercompilerOptions,watchOptionsortypeAcquisitionwhich are lists or object type eg.paths,typeRoots,libsetc.From the above example writing the
project1config as:per Andrew Branch (@andrewbranch) 's suggestion here: #56436 (comment)
other option is to write config as:
{ "compilerOptions": { "extend": { "paths": { "@/foo/*": ["../packages/foo/dist/*"] } } }, "extend": { "references": [ { "path": "../packages/foo" } ] } } // Note we probably need to call this merge since extends and extend are too close at root level ?Would mean that project1 wrote the tsconfig as:
Note how the paths still remain relative to config they are defined in but allowing one to add more properties and if say baseConfig also had rule for
@environment/*path mapping it is overwritten by the project1 specific. That is it does not recusively merge property values of path mappings.Apart from having ability to specify specific options that get merged, users have often asked us for a way to specify config such that base config will specify option say
outDirand instead of it being relative to the base config, it needs to be relative to project's tsconfig.For example in the above example, instead of all projects output going into
/temp/test/distthe output to be inside eachdistfolder of each project.Apart from
outDirthis would also help in writing base configs such that extendingbase.tsconfig.jsonwould include project'ssrcfiles and extendingbase.test.tsconfig.jsonwould includetestsfilesWith below configs:
Today the resulting config of project1 is:
Proposal here is to add property
rawwith names of properties in base config such that extending it would mean as if project extending it specified them, making them relative to final config instead of the base config.So with change to base.tsconfig.json as:
per Andrew Branch (@andrewbranch) suggestion option 2 to consider:
would result in final project1 config as if it wrote:
and another project2 say with
mergeproperty as:would result in configuration as if written as:
The property
rawcan be used for:outDir,declarationDiretcrootDirs,typeRootsfromcompilerOptionsorexcludeFiles,excludeDirectoriesfromwatchOptionsincludeandexcluderoot config properties. (filesandreferencesare not included here as not sure if they really make sense?)pathsis a special option where normally the base path (propertypathsBasePath) is relative to config they are declared in. So addingpathstorawwould mean that path mapping is done relative to config file extending the root config file.There was consideration of specifying
rawextend as part of config extending root config but that would mean either writing something like"rawExtend": ["outDir", "typeRoots"]or"merge": [{ "name": "include", "kind": "raw" }]in each config defeating the purpose of concise extend. Any feedback on that?Should
mergebe in root config: probably not because if project wants to override or add should be part of project decision and it would need to add properties to list only if that config specifies to making this property of project config makes more sense.TODO:
What happens to
rawandmergewhen multi-level extending is in play. Probably they need to be merged instead of overwritten but need to think about that.Here are issues this would help with:
#44589
#27098
#20110
#29172
📃 Motivating Example
A way to specify say project specific "paths" mapping without having to rewrite all the mappings from the base config.
And a way to specify root config that can specify
includeand/oroutDirand not needing to write than in each project.💻 Use Cases