[RFC]: Support ignoring tsconfig paths config

[chenjiahan]

What problem does this feature solve?

Currently, the Modern.js Builder automatically reads the compilerOptions.paths field in tsconfig.json as the alias config, and the priority of tsconfig paths is higher than source.alias config, so the source.alias is basically useless for TypeScript projects.

• Example for tsconfig paths:

{
  "compilerOptions": {
    "paths": {
      "@common/*": ["./src/common/*"]
    }
  }
}

• Example for source.alias:

export default {
  source: {
    alias: {
      '@common': './src/common',
    },
  },
};

Detailed document of the current behavior: https://modernjs.dev/builder/en/guide/advanced/alias.html

But in some scenarios, the user does not want the default behavior, they want to use source.alias because it allows user to create some alias config dynamically, for example, use process.env to set alias.

export default {
  source: {
    alias: {
      '@common':  process.env.NODE_ENV === 'production' ? './src/common-prod' : './src/common-dev',
    },
  },
};

And tsconfig paths config is static (written by JSON) and not as flexible as source.alias. In this case, tsconfig paths config is only used to provide the type of alias, and should not override the user configured alias config.

What does the proposed API look like?

The Modern.js Builder will add a new source.aliasStrategy config to change the default behavior, so users can use the source.alias and it will not be overridden by tsconfig paths.

• Type: 'prefer-tsconfig' | 'prefer-alias'
• Default: 'prefer-alias'
• Example:

export default {
  source: {
   aliasStrategy:'prefer-tsconfig',
  }
}

[fireairforce]

The specific implementation is to disable TsConfigPathsPlugin after the user configures source.ignoreTsConfigPaths as true?

[h-a-n-a]

Great RFC! Personally speaking, consistency with the original configuration is important. Since source.alias is known for the most of modern.js users and tsConfigPath is an implicit behavior, adding the new field may make user a little bit confused. I would love to use the alias related field to at least show the connection between the original field.

Second is the extendability.

Based on my considerations, I would like to propose something like source.aliasStrategy. The default value can be 'prefer-tsconfig'. For the extendability, users can pass array to specify the order of configurations in the future.

[chenjiahan]

The specific implementation is to disable TsConfigPathsPlugin after the user configures source.ignoreTsConfigPaths as true?

Yes, and when using Rspack, it will remove the resolve.tsConfigPaths config.

[chenjiahan]

I would like to propose something like source.aliasStrategy. The default value can be 'prefer-tsconfig'

Like this idea! I will update my RFC and use the source.aliasStrategy.

for the most of modern.js users and tsConfigPath is an implicit behavior

Considering that next.js reads tsconfig paths by default, maybe community users are more familiar with tsconfig paths rather than source alias.

I don't know if we will have other fields or configuration files that will be supported natively by modern.js.

Only tsconfig paths now. 😄

[KyrieLii]

Gread idea ! In addition, maybe we need to provide a configuration to specify the tsconfig.json file path.

The current implementation is hard-coded ${rootPath}/tsconfig.json.

[chenjiahan]

specify the tsconfig.json file path

@targeral have enhanced the TsConfigPathsPlugin in a recent PR: #3991

Now the plugin will find the closet tsconfig.json of each module, which is the same as the native typescript behavior.

[KyrieLii]

find the closet tsconfig.json of each module

What I mean is that the following configuration can be directly modified:
(Although we can now modify it through tools.bundlerChain.)

// webpack
new TsconfigPathsPlugin({
  configFile: 'xxx' // here
})

// rspack
resolve: {
    tsConfigPath: 'xxx', // here
  },

For example, some projects have diffrent tsconfig.web.json, tsconfig.node.json or tsconfig.dev.json, tsconfig.prod.json. 😅

[hardfist]

The specific implementation is to disable TsConfigPathsPlugin after the user configures source.ignoreTsConfigPaths as true?

Yes, and when using Rspack, it will remove the resolve.tsConfigPaths config.

things becomes complex now, since rspack tsconfig paths and alias are merged and tsconfig path has high priority, so it would be hard for rspack to implement the stragegy

[chenjiahan]

What I mean is that the following configuration can be directly modified

If the user asks for this config, we will consider adding it.

[chenjiahan]

things becomes complex now, since rspack tsconfig paths and alias are merged and tsconfig path has high priority, so it would be hard for rspack to implement the stragegy

We can just remove the resolve.tsConfigPaths config fro Modern.js Builder when using aliasStrategy:'prefer-alias'.

[hardfist]

We can just remove the resolve.tsConfigPaths config fro Modern.js Builder when using aliasStrategy:'prefer-tsconfig'.

you mean perfer-alias?

[chenjiahan]

you mean perfer-alias?

Yep, my mistake

[hardfist]

it seems rspack merge tsconfig.paths and alias if set tsconfigpaths which behaves not the same as prefer-tsconfig or prefer-alias

[chenjiahan]

rspack merge tsconfig.paths and alias

If the tsconfig.paths has a higher priority, then is it same as prefer-tsconfig.

[chenjiahan]

The Rspack documentation should explain more about the relationship between tsconfig.paths and resolve.alias.

[hardfist]

@bvanjoi @Boshen can you help check the result and help improve the documentation of resolve