Generate boundary's native dispatch from its .baml by codeshaunted · Pull Request #4116 · BoundaryML/baml

codeshaunted · 2026-07-22T01:21:06Z

Follow-up to #4099, which made baml_builtins2_codegen package-generic and moved reflect onto it. boundary was the last package still hand-wiring its natives.

What it was

pub fn get_native_fn(path: &str) -> Option<NativeFunction> {
    match path.strip_prefix("boundary.")? {
        "id" => Some(id::new),
        "id.current" => Some(id::current),
        "LocalId.capture" => Some(id::capture),
        _ => None,
    }
}

Nothing kept that in sync with the .baml declarations: adding a $rust_function and forgetting an arm gave a runtime lookup miss, not a build error. Each native also hand-rolled the boilerplate the generated glue already writes: arity checks, argument conversion, and the Result -> NativeCallResult match.

What it is now

boundary generates its BamlPackageBoundary / BamlNamespaceId / BamlClassLocalId hierarchy like baml and reflect (three lines in bex_vm/build.rs), so:

the three natives are required trait methods, and a declared $rust_function without an implementation is a compile error;
arguments arrive converted, so LocalId.capture takes Option<bool> triples instead of unpacking raw Values, and the hand-written optional_bool helper is deleted;
the LocalId constructor builds through the generated copy::LocalId struct instead of a positional alloc_instance(vec![...]);
VM_NATIVE_PACKAGES now points every package at a generated dispatcher, so no entry in it can drift.

Scope

I checked the other stdlib packages: log is entirely $compiler_intrinsic (no natives), and assert and testing declare none, so boundary was the only remaining offender.

Net +10 lines (the generation loop entry and trait scaffolding, minus the deleted dispatch and glue). Verified: bex_vm + baml_tests 2929 passing, baml_cli + bex_engine 976 passing, clippy clean.

Summary by CodeRabbit

Refactor
- Updated the Boundary runtime package to use the same generated native-function dispatch as other standard-library packages.
- Improved handling of Boundary IDs and local ID capture through typed interfaces.
- Preserved local ID capture behavior while simplifying argument handling and state management.
- Added generated Boundary native-function support to the build process.

boundary was the last package still hand-wiring its natives: a match over string paths that nothing kept in sync with the .baml declarations, plus per-native arity checks, argument conversion, and result-to-NativeCallResult boilerplate the generated glue already writes. It now goes through the generated BamlPackageBoundary hierarchy like baml and reflect: the three natives become required trait methods that receive converted arguments (LocalId.capture takes Option<bool> triples instead of unpacking raw Values), the LocalId constructor builds through the generated copy:: struct, and the hand-written optional_bool helper is gone. log, assert, and testing declare no natives (log is all compiler intrinsics), so no other package is affected.

vercel · 2026-07-22T01:21:12Z

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coderabbitai · 2026-07-22T01:21:28Z

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Repository UI

Review profile: CHILL

Plan: Pro

Run ID: 89c516f6-9632-4d48-92ac-5bff2e36dbb7

📥 Commits

Reviewing files that changed from the base of the PR and between 2c888e4 and ff00f57.

📒 Files selected for processing (4)

baml_language/crates/bex_vm/build.rs
baml_language/crates/bex_vm/src/package_baml/mod.rs
baml_language/crates/bex_vm/src/package_boundary/id.rs
baml_language/crates/bex_vm/src/package_boundary/mod.rs

📝 Walkthrough

Walkthrough

Boundary native functions are added to build-time generation, exposed through a generated module, and registered through the trait-based VM dispatcher. Boundary ID and LocalId entrypoints now use typed trait implementations and direct state/value conversions.

Changes

Boundary dispatcher migration

Layer / File(s)	Summary
Generate and expose boundary dispatch `baml_language/crates/bex_vm/build.rs`, `baml_language/crates/bex_vm/src/package_boundary/mod.rs`	Build generation now produces `boundaryfunctions_generated.rs`, which the boundary module includes and re-exports through `PackageBoundaryImpl`.
Implement typed boundary operations `baml_language/crates/bex_vm/src/package_boundary/id.rs`	Boundary ID and LocalId operations now use generated traits, typed optional booleans, and direct LocalId state/value conversion.
Register the boundary resolver `baml_language/crates/bex_vm/src/package_baml/mod.rs`	The VM registry routes `boundary.` calls through the generated `BamlPackageBoundary` resolver.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Possibly related PRs

BoundaryML/baml#4066: Related boundary.LocalId and runtime ID propagation changes.
BoundaryML/baml#4099: Related generated native-function dispatch changes.

Suggested reviewers: rossirpaulo, hellovai

Poem

A rabbit hops through generated code,
Boundary paths now share the road.
Typed IDs and LocalIds align,
With trait-bound dispatch in a neat design.
“No hand-wired trails!” the bunny sings,
As build-time magic grows new wings.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly matches the main change: generating boundary's native dispatch from its .baml declarations.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

📝 Generate docstrings

Create stacked PR
Commit on current branch

🧪 Generate unit tests (beta)

Create PR with unit tests
Commit unit tests in branch avery/native-dispatch-boundary

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github-actions · 2026-07-22T01:21:46Z

⏭️ Performance benchmarks were skipped

Perf benchmarks (CodSpeed) are opt-in on pull requests — they no longer run on every push. They always run automatically after merge to canary/main.

To run them on this PR, do any of the following, then push a commit (or re-run CI):

Add RUN_CODSPEED=1 to the PR description, or
Include run-perf or /perf in the PR title or any commit message.

github-actions · 2026-07-22T01:31:55Z

Binary size checks passed

✅ 7 passed

	Artifact	Platform	File	Gzip	Gated on	Baseline	Delta	Status
✅	`baml-cli`	Linux	🔒 25.6 MB	10.8 MB	file	25.3 MB	+275.0 KB (+1.1%)	OK
✅	`packed-program`	Linux	🔒 17.2 MB	7.1 MB	file	17.0 MB	+153.1 KB (+0.9%)	OK
✅	`baml-cli`	macOS	🔒 19.8 MB	9.4 MB	file	19.6 MB	+231.5 KB (+1.2%)	OK
✅	`packed-program`	macOS	🔒 13.4 MB	6.2 MB	file	13.2 MB	+198.3 KB (+1.5%)	OK
✅	`baml-cli`	Windows	🔒 21.3 MB	9.7 MB	file	21.1 MB	+230.9 KB (+1.1%)	OK
✅	`packed-program`	Windows	🔒 14.3 MB	6.3 MB	file	14.2 MB	+150.5 KB (+1.1%)	OK
✅	`bridge_wasm`	WASM	16.3 MB	🔒 4.4 MB	gzip	4.4 MB	+19.2 KB (+0.4%)	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.

Generated by cargo size-gate · workflow run

vercel Bot temporarily deployed to Preview – beps July 22, 2026 01:21 Inactive

coderabbitai Bot approved these changes Jul 22, 2026

View reviewed changes

vercel Bot temporarily deployed to Preview – promptfiddle2 July 22, 2026 01:29 Inactive

codeshaunted added this pull request to the merge queue Jul 22, 2026

vercel Bot temporarily deployed to Preview – promptfiddle July 22, 2026 01:42 Inactive

github-merge-queue Bot removed this pull request from the merge queue due to failed status checks Jul 22, 2026

codeshaunted added this pull request to the merge queue Jul 22, 2026

Merged via the queue into canary with commit 6951c86 Jul 22, 2026
66 checks passed

codeshaunted deleted the avery/native-dispatch-boundary branch July 22, 2026 01:52

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Generate boundary's native dispatch from its .baml - #4116

Generate boundary's native dispatch from its .baml#4116
codeshaunted merged 1 commit into
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What it was

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