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feat(ruby): Ruby language bindings by omarqureshi · Pull Request #5178 · aws/jsii · GitHub
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feat(ruby): Ruby language bindings - #5178

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omarqureshi:ruby-language-bindings
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feat(ruby): Ruby language bindings#5178
omarqureshi wants to merge 7 commits into
aws:mainfrom
omarqureshi:ruby-language-bindings

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@omarqureshi

@omarqureshi omarqureshi commented Jun 20, 2026 •
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Objective

Introduces comprehensive Ruby language bindings for the jsii ecosystem, enabling AWS CDK (and other jsii-based libraries) to be packaged as gems and consumed idiomatically from Ruby. It adds the code-generation target (jsii-pacmak) and the core Ruby runtime (@jsii/ruby-runtime), with strict type-safety, careful object lifecycle management, and thread-safe IPC with the jsii Node kernel.

Implements RFC 0935: Ruby language bindings. The change is strictly additive — no breaking changes to existing languages and no assembly-format change beyond an additive targets.ruby schema extension.

Warning

CI is expected to be red on this branch, by design. Ruby code generation requires a jsii-compiler release with Ruby target support, which is not yet published. Until it is, the following failures are expected and are not indicative of broken work:

  • jsii-pacmak target-ruby snapshot test — this branch builds with the stock compiler (no Ruby support), so the committed assemblies carry no targets.ruby and generated names won't match the snapshot.
  • @jsii/ruby-runtime-test (generate.sh + rspec) — cannot generate the Ruby lib/ without the Ruby-capable compiler.
  • "Assert clean working directory" — a build would rewrite the assemblies.

Once the Ruby-capable compiler is released, the committed fixtures (assemblies with targets.ruby + the Ruby snapshot) are regenerated against it and CI goes green. End-to-end regeneration + publish has already been validated against the fork compiler.

Key Components

1. Code Generation (jsii-pacmak)

  • RubyTarget & RubyGenerator (packages/jsii-pacmak/lib/targets/ruby.ts): translate jsii types into idiomatic Ruby — class < Jsii::Object, behavioral interfaces as mixin modules, datatype structs as kwargs value-classes (< Jsii::Struct), enums as Jsii::Enum wrapper constants, async + sync methods, and property/method overrides.
  • Generated RBS signatures: every class, module, method, and struct gets a .rbs; output validates clean under rbs validate across jsii-calc and its dependency closure.
  • Idiomatic naming: snake_case members, PascalCase modules (configurable acronyms), UPPER_SNAKE constants, reserved-word mangling (next → _next). Root namespace AWSCDK with AWS-prefix de-duplication (aws-s3 → AWSCDK::S3::Bucket).
  • Robust namespacing: pre-declares Ruby namespaces (module X; end) in dependency order to prevent NameError during nested type generation.
  • Security & type checking: injects Jsii::Type.check_type for runtime enforcement, and embeds type metadata as Base64-encoded JSON literals so no jsii-supplied identifier or docstring can inject into generated source via string interpolation.
  • Version management: shared version-utils.ts translates npm semver (incl. pre-release .alpha.1/.dev.1) to RubyGems ranges.

2. Ruby Runtime Core (@jsii/ruby-runtime)

  • Thread-safe IPC kernel: a re-entrant Monitor makes the bidirectional JSON-RPC stdio pipe safe under concurrency and re-entrant callbacks; an isolated stderr-draining thread prevents pipe deadlocks.
  • Callbacks & overrides: JS→Ruby callbacks (including super crossing back to the JS implementation), with user subclasses detected at construction time.
  • Object registry & lifecycle: proxies created via .allocate, mapped by $jsii.byref; deliberately never issues a guest-initiated del (matching the Python/Go runtimes) — cleanup is wholesale on kernel shutdown, which suits short-lived synth workloads.
  • Type-driven serialization: a dedicated Jsii::Serializer (rather than monkey-patching core types) handles by-value structs vs by-reference objects, avoiding leakage of host application state.

3. Compliance & Testing (@jsii/ruby-runtime-test)

  • Full compliance suite covering all 123 canonical compliance cases (diamond inheritance, async/sync overrides, property overrides, hash coercion, unions, nullability, collections, naming).
  • Ruby-specific unit specs: serializer round-trips, kernel concurrency, lazy autoload, and rbs validate. No skipped/pending tests.

4. CI / Build

  • GitHub Actions: Ruby 3.3 set up on every matrix leg, plus dedicated Ruby 3.4 and 4.0 legs; buildspec.yaml CodeBuild runtime added.
  • Wired into the compliance report (tools/jsii-compliance).

Compatibility & Known Limitations

  • Ruby 3.3+ on MRI (CRuby) only — gemspecs enforce required_ruby_version >= 3.3.0 (3.1/3.2 are EOL). JRuby/TruffleRuby are out of scope for the initial release.
  • Ambiguous unions: a Hash passed where a union admits more than one struct type is forwarded as-is; coercion only happens when exactly one struct arm makes it unambiguous.
  • Hash keys must be snake_case when supplied for struct coercion.
  • Async static methods go through the synchronous kernel path (the kernel's begin API only accepts object references — a limitation shared by all bindings).

Notes & Next Steps

  • Rosetta: the jsii-rosetta translation backend for Ruby is not included here and will follow in a subsequent PR.
  • Test fixtures: the committed test assemblies currently follow main and do not yet carry targets.ruby (it's compiler-generated). They — and the target-ruby snapshot — will be regenerated against the released Ruby-capable compiler before merge. See the warning above.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

How to review this PR

The branch history is organized into seven self-contained review units, ordered so the
cross-cutting surface comes first and the large pure-addition trees are isolated. Total
shared-file footprint outside new ruby-* trees: 8 files (spec configuration,
version-utils + its test, pacmak target registration, kernel.test.ts naming expectations,
compliance suite/report, CI matrix, tsconfig-base, one build-tools glob).

# Commit Scope Size
1 feat(spec) targets.ruby schema — the only assembly-facing change 1 file, +16
2 feat(pacmak) Ruby version-range support in shared version-utils, with tests 2 files, +199
3 feat(ruby) @jsii/ruby-runtime — the runtime gem (pure addition) 26 files, +2,510
4 feat(pacmak) the Ruby code-generation target (new file + 2-line registration; the bulk is the generated-code snapshot) 6 files, +26,593
5 test(ruby) runtime test suite + fixture targets.ruby declarations 42 files, +3,916
6 test(compliance) compliance-matrix wiring; absent report files render n/a (not a false 0.00%) 3 files, ±144/127
7 ci build-matrix rows + ignoreDeprecations (called out for review in the commit message) 4 files, +81

Suggested reading order: 1 → 2 → 7 → 6 (the entire cross-cutting surface, ~15 minutes) —
then 3 (the runtime) and 5 (its tests) as one unit, and 4 last (of its +26.6k, ~24k is the
committed generated-code snapshot; the generator itself is lib/targets/ruby.ts, ~2.4k lines).

Checks on this PR stay red until aws/jsii-compiler#2663
merges and releases (the branch builds against that schema); green full-matrix runs exist on
the branch and the daily preview pipeline smoke-tests the published output — sequencing in
the RFC's Upstreaming sequence section (aws/aws-cdk-rfcs#939).

This was referenced Jul 4, 2026
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@omarqureshi
omarqureshi force-pushed the ruby-language-bindings branch from 0ea38eb to d2c88dd Compare July 15, 2026 08:12
@omarqureshi
omarqureshi force-pushed the ruby-language-bindings branch from 7295d63 to e7e2ca2 Compare July 23, 2026 09:58
@omarqureshi
feat(spec): add ruby to the assembly targets configuration
8a4b820 
Additive schema only: `ruby { gem, module, acronyms? }` joins the existing
per-language target blocks. The `.jsii` assembly format is unchanged —
AssemblyTargets already carries an index signature, so existing assemblies
and every other language are unaffected.
@omarqureshi
feat(pacmak): Ruby version-range and release-version support
5fb432d 
toRubyVersionRange converts semver ranges to RubyGems requirement syntax
(throwing on `||` OR-ranges, which Gem::Requirement cannot express), and
toReleaseVersion gains a RUBY case with a strict prerelease-label grammar.
Shared file, self-contained change, fully covered in version-utils.test.ts
including the error paths.
@omarqureshi
feat(ruby): the @jsii/ruby-runtime gem
54f7c9f 
Pure addition. The Ruby guest runtime: a Monitor-serialized kernel driving
the standard Node sidecar over line-delimited JSON (all twelve wire verbs),
a type-driven serializer for every value envelope, override discovery from
generated metadata tables, hash-to-struct and Proc-to-interface (SAM)
coercion, lazy type registration/hydration, and an error taxonomy that
separates kernel faults from remote JS exceptions. Hand-written RBS
signatures under sig/. No dependencies beyond stdlib + base64 (a Ruby
3.4+ default-gem unbundling requirement).
@omarqureshi
omarqureshi force-pushed the ruby-language-bindings branch 2 times, most recently from 0dc40de to f4a25f4 Compare July 23, 2026 21:01
@omarqureshi
feat(pacmak): the Ruby code-generation target
d62d502 
The generator (lib/targets/ruby.ts, new file): classes with flattened
member re-emission so `super` works in guest overrides, interfaces as
modules, structs with keyword constructors, enums, per-assembly acronym
config read from targets.ruby (no built-in lists), lazy loading via paired
autoload registration, RBS signature emission, YARD docs with
rosetta-translated examples, reserved-word escaping synced with the
runtime, and injection-safe string escaping at every interpolation site.

Cross-cutting surface is two lines in lib/targets/index.ts (target
registration) and a one-line generalization of package-ruby.bin's gemspec
glob. Coverage: the target-ruby snapshot corpus over jsii-calc plus
focused naming/casing tests.
@omarqureshi
test(ruby): runtime test suite and fixture enablement
207ed4b 
packages/@jsii/ruby-runtime-test (new): 14 compliance spec files tagged
case-for-case against tools/jsii-compliance/suite.ts, plus unit specs for
the riskiest machinery (autoload, callbacks, serializer, SAM coercion,
concurrency, RBS validation with a negative control). generate.sh
regenerates the jsii-calc bindings unconditionally so specs can never run
against stale generated code.

Enablement edits outside the new package: targets.ruby declarations on the
four jsii-calc fixture assemblies, matching ruby naming expectations in
@jsii/kernel's kernel.test.ts, and a bash shebang on update-all.sh.
@omarqureshi
test(compliance): wire Ruby into the compliance matrix; report n/a ho…
1cd2e21 
…nestly

suite.ts registers the ruby binding's report path. report.ts previously
iterated the report files present on disk; it now iterates the declared
bindings, which surfaces a latent presentation bug: a language whose
report file is absent in a given checkout would render as a false 0.00%.
Absent reports now render as "n/a" cells with an (n/a) header — languages
with report files are computed exactly as before, and the regenerated
gh-pages report reflects both changes.
@omarqureshi
ci: Ruby in the build matrix; TypeScript 6 toolchain accommodation
0514baf 
Ruby 3.3 joins every job's setup and the OS matrix gains Ruby 3.4 and 4.0
rows (Linux/macOS/Windows). yarn.lock carries the ruby-runtime test
package's dependency graph.

tsconfig-base.json gains ignoreDeprecations "6.0": the shared compiler
options include settings TypeScript 6 flags as deprecated, and the Ruby
target was developed against a TS 6 toolchain. This is repo-wide and
deliberately surfaced here for review — it can be dropped if the
mainline toolchain does not need it.
@omarqureshi
omarqureshi force-pushed the ruby-language-bindings branch from f4a25f4 to 0514baf Compare July 24, 2026 08:59
@yuuu

yuuu commented Oct 7, 2026

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Hi, and thank you for the large amount of work on this. This is my first time engaging with this repository, but I'm looking forward to Ruby support, so I tried the PR locally and wanted to share what I found.

What I tried

I rebased the branch onto the latest main (ddc88f3) and ran the tests locally:

  • @jsii/ruby-runtime-test: 280 examples, 0 failures (Ruby 4.0.6)
  • pacmak Ruby unit tests: all 19 pass
  • My environment has no dotnet or java, so I couldn't verify the full yarn build.

The rebase conflicts were limited to 6-compliance-report.md and .github/workflows/main.yml (the Go 1.25 entry that main has since removed).

Questions

I may be missing context, so please take these as questions rather than suggestions:

  1. Without jsii-compiler#2663 and jsii-rosetta#3710 merged, the fixture build failed with Unknown target language: ruby. Is my understanding right that the merge order is compiler, rosetta, then jsii?
  2. Are jsii-config support for Ruby and the gh-pages documentation planned as separate PRs?

I'd be glad to help with any of this if it's useful. Please feel free to disregard anything that misses the mark.

@omarqureshi

omarqureshi commented Oct 9, 2026

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Hi @yuuu - work on this has been scrapped in favour of a language plugin system due to maintenance concerns with an official Ruby language, I will have something to share on this in the next week. Unfortunately work commitments have been very hectic

I would have a read of https://github.com/omarqureshi/aws-cdk-rfcs/blob/4721527e92fc7cd582671cde7d3837102a200ab8/text/0000-jsii-language-plugins.md

with https://github.com/omarqureshi/jsii-target-ruby as an implementation

@omarqureshi

omarqureshi commented Oct 9, 2026

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Another thing you can try is have a read of https://rubygems.omarqureshi.net/ - these gems are by no means up to date but they are a usable CDK implementation in Ruby

@omarqureshi

omarqureshi commented Oct 11, 2026

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This is superseded by the plugin approach in RFC aws/aws-cdk-rfcs#1005 (RFC text), which follows the discussion that closed aws/aws-cdk-rfcs#935. Rather than adding Ruby to this repository, the RFC opens the seams an out-of-tree language target needs, and Ruby becomes the first plugin (omarqureshi/jsii-target-ruby).

In this repository, the plugin work is the --plugin seam in jsii-pacmak (PR to follow), plus #5274, a standalone fix for a --recurse bug that affects every target.

I'm leaving this open as a reference until the RFC has a decision, and will close it then.

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2 participants

@omarqureshi @yuuu