microsoft / microsoft/TypeScript

[Breaking Change] Typescript 3.7 converts reference paths to tsconfig specified paths breaking multi-project compiles.

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Description

Typescript is replacing part of a relative path with one of the paths specified in tsconfig's path section. This is breaking the projects that rely on this file as they cannot resolve the path.

TypeScript Version: 3.7
Visual Studio Version: Community 2017

Search Terms:
Typescirpt paths tsconfig reference paths alias.

Code

In the client project at folder\folder\file.ts

/// <reference path="../../External/Knockout/index.d.ts" />

Becomes (in ClientDeclarations) folder\folder\file.d.ts:

/// <reference types="@Client/external/knockout/index" />

My tsconfig file (folder names with sensitive information are replaced with ***)

{
  "compileOnSave": true,
  "compilerOptions": {
    "module": "amd",
    "target": "es6",
    "lib": [ "es6", "dom" ],
    "sourceMap": true,
    "strict": true,
    "build": true,
    "declaration": true,
    "declarationDir": "../ClientDeclarations",
    "baseUrl": "./",
    "paths": {
      "@Common/*": [ "../Common/*" ],
      "@Server/*": [ "../ServerDeclarations/*" ],
      "@Client/*": [ "./*"]
    }
  },
  "include": [
    "./*",
    "./External/***/koco.ts",
    "./External/***/kocss.ts",
    "./External/***/kopath.ts"
  ],
  "exclude": [
    "node_modules"
  ],
  "references": [
    { "path": "../Common" }
  ]
}

Expected behavior:
The path should not be transformed during output.

Actual behavior:
The path is transformed to include an @Client reference, which my dependant projects can't resolve. This did not happen in tsc 3.4.

Additionally all of the casing is altered - meaning that this path would not resolve on linux machines.

Related Issues:
I haven't been able to find any - probably because what I'm trying to look for is called a "path" (in tsconfig) which is a highly overloaded term, making searching for anything related to it almost impossible. It would be nice to call it something like a "path alias" so that searching for related issues was easier.

Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Reproduce the declaration output with tsc 3.7 using the shown tsconfig paths, project reference, and relative /// reference path, then compare it with tsc 3.4. Trace how declaration emit converts the reference and casing. Done means the relative reference remains resolvable in dependent projects without an incorrect @Client alias or casing change.

Written by the indexing model from the issue text.

Assessment

Tech stack
typescript
Domain
build-system, compilers
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
35/100

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