Use pnpm workspaces for our Typescript monorepo

[pokey]

Just a rough draft

Context

The issue motivating this decision, and any context that influences or constrains the decision.

Desiderata

Note that the import and auto-import tests can be checked by applying this patch and then uncommenting the last line of each block one by one and checking whether error is flagged / not flagged (for import tests), or whether suggestion appears / doesn't appear in auto-complete (for auto-import tests). Make sure to comment the line again before trying the next one, as sometimes a bad import can affect other imports (packages can "collapse" into one from the perspective of TS server)

Correctly flagging errors

• D1: It is a compile error to import external packages that are not listed in package.json
  • D1.1: vscode (for some reason this one behaves strangely)
  • D1.2: Other packages
• D2: It is not a compile error to import from local packages that you depend on, using our preferred syntax (eg @cursorless/foo)
• D3: It is a compile error to import from local packages that you depend on, not using our preferred syntax (eg ../foo)
• D4: It is a compile error to import from local packages that you do not depend on, either
  • D4.1: using our non-preferred syntax (eg ../packages/foo), or
  • D4.2: using preferred syntax (eg @cursorless/foo)
• D5: It is a compile error to import from anything other than index.ts in another module
  • D5.1: no @cursorless/foo/bar
  • D5.2: no ../foo/bar
  • a: Even if you depend on the module
  • b: Even if bar was re-exported in foo/index.ts. In that case it should be required to import @cursorless/foo
• D6: It is not a compile error to import external packages listed in package.json
  • D6.1: vscode (for some reason this one behaves strangely)
  • D6.2: Other packages

Auto-import

• D7: Auto-import doesn't import from external packages not listed in package.json
  • D7.1: vscode (for some reason this one behaves strangely)
  • D7.2: Other packages
• D8: Auto-import imports from external packages listed in package.json
  • D8.1: vscode (for some reason this one behaves strangely)
  • D8.2: Other packages
• D9: Auto-import imports from local packages that you depend on, using our preferred syntax (eg @cursorless/foo)
• D10: Auto-import doesn't import from local packages that you don't depend on
• D11: Auto-import doesn't import from anything other than index.ts in another package (eg no @cursorless/foo/bar)
  • D11.1: When you depend on the package
  • D11.2: When you don't depend on the package

Other DX

• D12: Find references across projects when no file from the referencing project is open
• D13: Rename across projects when no file from the referencing project is open
• D14: Jump to definition across projects
• D15: It is easy to move a file from one package to another
• D16: It is easy to create a new package
• D17: Breakpoints work in Cursorless extension
• D18: Breakpoints work on Cursorless root website
• D19: Breakpoints work on Cursorless docs website

Options considered

• nx
• npm workspaces
• pnpm workspaces

Decision

The change that we're proposing or have agreed to implement.

Consequences

What becomes easier or more difficult to do and any risks introduced by the change that will need to be mitigated.