Deprecate, remove support for baseUrl #62207
Description
Today, baseUrl performs two functions:
- it acts as a prefix for all entries in
paths - it acts as a potential resolution point for all bare paths
But almost nobody realizes that last part. It means if you have the following:
{
"compilerOptions": {
// ...
"baseUrl": "./src",
"paths": {
"@app/*": ["app/*"],
"@lib/*": ["lib/*"]
}
}
}An import like
import * as blah from "blah.js";might resolve to any of the following paths
./src/app/blah.js./src/lib/blah.js./src/blah.js⚠️
That last resolution is usually undesirable. Often though, people specify a baseUrl because it was previously required to make paths work.
In TypeScript 7.0, we are not reimplementing baseUrl.
Instead, paths will need to manually specify a custom prefix.
{
"compilerOptions": {
// ...
- "baseUrl": "./src",
"paths": {
- "@app/*": ["app/*"],
- "@lib/*": ["lib/*"]
+ "@app/*": ["./src/app/*"],
+ "@lib/*": ["./src/lib/*"]
}
}
}In the event that you want to maintain the same behavior as before, you can add an additional path mapping for the baseUrl itself:
{
"compilerOptions": {
// ...
"paths": {
// A new catch-all that replaces the baseUrl:
"*": ["./src/*"],
// Every other path now has an explicit common prefix:
"@app/*": ["./src/app/*"],
"@lib/*": ["./src/lib/*"],
}
}
}In TypeScript 6.0, we will be deprecating this behavior. Using baseUrl will lead to an error which can only be resolved by applying one of the above fixes, or using --ignoreDeprecations.