Resolve dot-qualified builtin class methods in baml describe

[ATX24]

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Issue Reference

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• This PR fixes/closes #[issue number]

Changes

Please describe the changes proposed in this pull request

The error

Given a minimal project:

function dummy(x: int) -> int { x }

Before this change, the natural method lookup failed:

$ baml describe Array.reduce
No symbol found: Array.reduce

The command exited with code 4 even though reduce is a builtin instance method on Array.

Root cause

baml_language/crates/baml_cli/src/describe_command.rs::dispatch handled explicit builtin package paths (baml.Array.reduce), lowercase primitive aliases (string.length), keywords, root.*, and user-package structural paths. For an unqualified builtin class member like Array.reduce, user-package resolution returned None, then the CLI fell back to substring describe with the whole string Array.reduce as an opaque symbol name. That fallback never reaches describe_item_member, so it printed No symbol found.

Once Array.reduce resolved, baml_language/crates/baml_lsp2_actions/src/describe.rs::render_method_signature also needed to include method-level generic parameters from Function::generic_params; otherwise generic builtin methods documented their callback types without the <A, E> surface.

The fix

• Added a narrowly scoped builtin class-member resolver in describe_command::dispatch after user-package resolution fails. It recognizes Class.method, searches non-user packages for a unique builtin class with that short name, and returns ResolvedTarget::Member so the existing class-method renderer is used.
• Preserved user-project precedence: a user Class.method structural target still resolves before builtin fallback.
• Updated method signature rendering to include method generic parameters and generic bounds.
• Added focused CLI dispatch tests for Array.reduce and String.split without the baml. package prefix.

Verification

Same reproduction after the change:

$ cargo run -p baml_cli -- describe Array.reduce --from /tmp
warning: using the internal BAML toolchain binary directly is not recommended. Use `baml` instead.
method reduce  <builtin>/baml/containers.baml:224-226

function reduce<A, E>(self, reducer: (A, T) -> A throws E, initial: A) -> A throws E

container:
  class            Array                            <builtin>/baml/containers.baml:2

references (0):

Commands run:

$ cargo test -p baml_cli without_package_prefix
running 2 tests
...
test result: ok. 2 passed; 0 failed; 0 ignored; 0 measured; 183 filtered out; finished in 0.26s

$ cargo test -p baml_cli --lib && cargo test -p baml_lsp2_actions --lib
# baml_cli
test result: ok. 185 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out
# baml_lsp2_actions
test result: ok. 114 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out

$ LD_LIBRARY_PATH=/home/ubuntu/.local/share/mise/installs/python/3.13.13/lib:${LD_LIBRARY_PATH:-} \
  cargo test --workspace --lib --exclude bridge_nodejs
...
test result: ok

I also attempted unexcluded cargo test --lib; it is blocked in this environment by bridge_nodejs test-linking against Node N-API symbols while the installed mise Node reports node_shared=false and provides no libnode.so.

Testing

Please describe how you tested these changes

• Unit tests added/updated
• Manual testing performed
• Tested in Linux Cursor Cloud environment

Screenshots

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Not applicable.

PR Checklist

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• I have read and followed the contributing guidelines
• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation where applicable
• My changes generate no new warnings

Additional Notes

Add any other context about the PR here

The setup required pnpm install, pnpm --filter @boundaryml/baml-core-node build:debug, and CI=1 ./setup.sh under baml_language/sdk_tests/crates/typescript_node so the TypeScript SDK harness fixtures had their generated node_modules trees.

  

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[github-actions]

Binary size checks passed

✅ 7 passed

	Artifact	Platform	File	Gzip	Gated on	Baseline	Delta	Status
✅	baml-cli	Linux	🔒 17.8 MB	7.6 MB	file	24.1 MB	-6.3 MB (-26.2%)	OK
✅	packed-program	Linux	🔒 12.9 MB	5.5 MB	file	15.1 MB	-2.2 MB (-14.6%)	OK
✅	baml-cli	macOS	🔒 13.6 MB	6.6 MB	file	18.2 MB	-4.6 MB (-25.4%)	OK
✅	packed-program	macOS	🔒 9.8 MB	4.8 MB	file	11.5 MB	-1.7 MB (-14.4%)	OK
✅	baml-cli	Windows	🔒 14.6 MB	6.7 MB	file	19.6 MB	-5.0 MB (-25.5%)	OK
✅	packed-program	Windows	🔒 10.4 MB	4.8 MB	file	12.2 MB	-1.8 MB (-15.0%)	OK
✅	bridge_wasm	WASM	11.9 MB	🔒 3.4 MB	gzip	3.9 MB	-504.5 KB (-13.0%)	OK

🔒 = the size this artifact is GATED on (ceiling + delta). Binaries gate on file size (installed binary); WASM gates on gzip (download size). The other size is shown for information only.

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