support to output declaration files or .dts on build or service.transform

[aelbore]

in typescript you can add on tsconfig.json "declaration": true, it can output or produce dts files. hope you can support on this :)
by the way nice work.

[evanw]

This is not something that I'm planning to support. The parser in esbuild skips over type annotations as if they were whitespace, so the AST doesn't contain any type annotations. This means esbuild doesn't have the information necessary to generate a .d.ts file.

[aelbore]

@evanw thanks for the reply, we can close this or reopen if soon its in your roadmap.
nice work.

[jaredpalmer]

@evanw I was just speaking with client at [redacted] (2nd or 3rd largest user of TS in the world). They believe you could potentially solve this by parsing files and stripping away implementation, in a second pass, but only keeping annotations and signatures. This isn't how the actual TS compiler does it, it's much more complex. However, according to [redacted], the above solution would work and be extremely fast.

Another reason you might want to take up this issue is that esbuild would become THE go to way of compiling all things TS, not just apps. Food for thought.

[wgebczyk]

@evanw I would as well like to get support to generate .d.ts - I'm not Xnd largest user of TS, but still like to have that option. Maybe you could point into place where such support might be placed and I would try myself to add it?

Of course if your vision for this tool is that it will not be supported, then of course will stop complaining about that.

[a-b-r-o-w-n]

Also consider library authors that want to use esbuild to compile their TS library but still include *.d.ts files for users. Right now, there is an additional burden on the package author to complicate their build process by requiring multiple steps (esbuild + tsc), and reduces the overall value of esbuild by increasing the time to compile.

I have experimented with creating a plugin that emits declaration files, but the typescript api is not well suited for parsing a single file at a time and the plugin api doesn't offer a way to do work after all files have been processed -- thus creating a bottleneck.

@evanw Do you have any thoughts for library maintainers on this? Is your guidance to use a mutli-stage build? If I'm still forced to use the typescript compiler, is there still a compelling reason to use esbuild?

[ycjcl868]

+1

[ycjcl868]

Also consider library authors that want to use esbuild to compile their TS library but still include *.d.ts files for users. Right now, there is an additional burden on the package author to complicate their build process by requiring multiple steps (esbuild + tsc), and reduces the overall value of esbuild by increasing the time to compile.

I have experimented with creating a plugin that emits declaration files, but the typescript api is not well suited for parsing a single file at a time and the plugin api doesn't offer a way to do work after all files have been processed -- thus creating a bottleneck.

@evanw Do you have any thoughts for library maintainers on this? Is your guidance to use a mutli-stage build? If I'm still forced to use the typescript compiler, is there still a compelling reason to use esbuild?

I think a reason is the bundled speed faster than other tools.

esbuild for bundled and tsc --emitDeclarationOnly for declaration might be the current solution, for example: esbuild src/index.ts --bundle --platform=node --target=node10 --outdir=dist && tsc --emitDeclarationOnly --outDir dist

[mattrossman]

@ycjcl868 Have you found a way to speed up the declarations step? It seems silly that esbuild can finish the bundle in a fraction of a second, while tsc takes multiple seconds just to extract types.

[jalal246]

@mattrossman This is really a good point and a real struggle. You bundle the whole project in less than a second then you have to wait to emit types. Feels like I am doing something wrong. Another point when bundling external dependency, the code is already bundled successfully but I have to find a way to include the external types.

[prantlf]

Another fast TypeScript compiler (swc) lacks this feature too, but according to their main developer it should be possible to implement.

[splashsky]

I agree on this Issue - Webpack has a neat plugin to bundle declaration files neatly into a single-file declaration. I want to advocate esbuild as much as possible, and this seems like a really common sense feature to focus on.