@typespec/prettier-plugin-typespec errors with Prettier 3.0.0

[eddyashton]

Prettier 3.0.0 was released yesterday, and throws errors when attempting to format any TypeSpec files.

Looking at a minimised snippet from one of the samples:

// main.tsp
import "@typespec/versioning";
import "@typespec/rest";
import "./library.tsp";

using TypeSpec.Versioning;
using TypeSpec.Rest;

@service({
  title: "Pet Store Service",
})
@versioned(Versions)
namespace VersionedApi;
using TypeSpec.Http;

enum Versions {
  @useDependency(Library.Versions.`1.0`)
  v1,

  @useDependency(Library.Versions.`1.1`)
  v2,
}

And a simple Prettier config:

{
  "plugins": [
    "@typespec/prettier-plugin-typespec"
  ],
  "overrides": [
    {
      "files": "*.tsp",
      "options": {
        "parser": "typespec"
      }
    }
  ]
}

The plugin works with 2.8.7:

$ prettier --version
2.8.7

$ prettier --write main.tsp 
main.tsp 9ms

But throws errors with 3.0.0:

$ npx prettier --version
3.0.0

$ npx prettier --write main.tsp 
main.tsp
[error] main.tsp: InvalidDocError: Unexpected doc.type 'concat'.
[error] Expected it to be 'cursor', 'indent', 'align', 'trim', 'group', 'fill', 'if-break', 'indent-if-break', 'line-suffix', 'line-suffix-boundary', 'line', 'label', or 'break-parent'.
[error]     at traverseDoc (file:///data/src/2.CCF/node_modules/prettier/index.mjs:15105:13)
[error]     at propagateBreaks (file:///data/src/2.CCF/node_modules/prettier/index.mjs:15437:3)
[error]     at printDocToString (file:///data/src/2.CCF/node_modules/prettier/index.mjs:15842:3)
[error]     at coreFormat (file:///data/src/2.CCF/node_modules/prettier/index.mjs:18409:18)
[error]     at async formatWithCursor (file:///data/src/2.CCF/node_modules/prettier/index.mjs:18603:14)
[error]     at async formatFiles (file:///data/src/2.CCF/node_modules/prettier/internal/cli.mjs:6778:18)
[error]     at async main (file:///data/src/2.CCF/node_modules/prettier/internal/cli.mjs:6970:5)
[error]     at async Module.run (file:///data/src/2.CCF/node_modules/prettier/internal/cli.mjs:6924:5)

[timotheeguerin]

I have a tentative PR #2157 adding support but I think there we also need to other plugins to update. In particular we are using sort-import plugin in our own repo and would need to be updated.

Updating to 3.0 is a decent breaking change and not sure we can keep back compat with prettier 2.0 which is also something to take into account.

[timotheeguerin]

Ok so actually those concern above are not a problem, everything seems to work fine. Plugin is backward compatible with prettier 2.0(At least for now)

The main issue is the breaking change to the prettier api which cascade into our api of making format async. This ends up causing a breaking change in the emitter framework as well.