[tomatotomata]

Description of the change

Reinstates the spago script command from the documented interface in issue #1000.

The command accepts a standalone Main module, optional --package-set, and repeatable -d/--dependency flags. It creates a temporary workspace for dependency resolution and compilation, then runs the generated program from the caller's directory so relative file operations behave as expected. The existing README already documents this interface.

Checklist:

• Added the change to the "Unreleased" section of the changelog
• Added some example of the new feature to the README (the existing example now works)
• Added a test for the contribution

Verification

• purs-tidy check passed for the changed PureScript files.
• spago build -p spago-bin passed with zero warnings and errors.
• The focused Windows smoke test passed: spago script -d node-fs test-fixtures/spago-script-make-file.purs wrote HELLO in the caller's directory.
• The full test command currently reaches the existing Windows purs graph invocation failure before running the suite.

Closes #1000

[thomashoneyman]

Can we make npm packages installed in the caller’s project available to the generated script? Setting executeDir preserves relative file operations, but Node resolves ESM package imports relative to the importing module, which is still under the temporary workspace.

I reproduced this with xhr2 installed in the caller directory and a script using affjax-node:

spago script --package-set 41.2.0 -d affjax-node npm-dependency.purs

Compilation succeeds, but execution fails with ERR_MODULE_NOT_FOUND: Cannot find package 'xhr2'. Importing xhr2 directly from the caller directory works. Linking the caller’s node_modules into the temporary workspace also makes the same generated program run successfully.

Could we cover this case alongside the existing node-fs test? That test only needs Node built-ins, so it doesn’t catch package resolution.

[thomashoneyman]

Could we clean up tmpDir when the command finishes, including failure paths? mkTemp only generates a pathname; it doesn’t arrange cleanup. This branch restores the working directory without removing the workspace.

We'd need to account for the direct Process.exit calls on error paths as well; adding only an Aff finally around this block wouldn’t cover those exits.