bun init: add react + @types/react to the blank scaffold so .tsx works

[robobun]

What does this PR do?

Fixes #5056.

The blank bun init -y scaffold writes a tsconfig.json with "jsx": "react-jsx", which makes both bun run file.tsx and tsc --noEmit try to resolve react/jsx-runtime. Because the scaffold did not install react or @types/react, dropping a .tsx file into a fresh project failed out of the box:

$ bun init -y && cat > react.tsx <<'TSX'
function Component(props: { message: string }): any {
  return <h1 style={{ color: "red" }}>{props.message}</h1>;
}
console.log(<Component message="Hello world!" />);
TSX

$ bun run react.tsx
error: Cannot find module 'react/jsx-dev-runtime' from '.../react.tsx'

$ bunx tsc --noEmit
react.tsx(2,10): error TS7026: JSX element implicitly has type 'any' because no interface 'JSX.IntrinsicElements' exists.
react.tsx(2,10): error TS2875: This JSX tag requires the module path 'react/jsx-runtime' to exist, but none could be found.

This treats react the same way the scaffold already treats typescript: add react to peerDependencies and @types/react to devDependencies when neither is present, skip under --minimal, and leave any existing react setup alone.

After:

$ bun init -y
...
+ @types/bun@1.3.14
+ @types/react@19.2.18
+ react@19.2.8
+ typescript@6.0.3
8 packages installed

$ bun run react.tsx
<Component message="Hello world!" />

$ bunx tsc --noEmit
$ echo $?
0

How did you verify your code works?

New tests in test/cli/init/init.test.ts:

• bun init -y: a .tsx file runs and typechecks out of the box runs bun init -y, writes a .tsx file, then asserts bun run succeeds and tsc --noEmit exits 0
• bun init leaves an existing react dependency alone asserts a pre-existing dependencies.react is not moved or duplicated
• --minimal test now asserts peerDependencies is absent and devDependencies is exactly { "@types/bun": "latest" }

Existing snapshot tests updated for the new package.json shape. All 17 tests in the file pass under bun bd test; the new .tsx test fails under USE_SYSTEM_BUN=1 at the first toHaveProperty("react") assertion.

---

no test proof · iteration 0 · Platform-specific test(s) that do not run on this machine. Deferring to CI, which covers all platforms: test/cli/init/init.test.ts

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📥 Commits

Reviewing files that changed from the base of the PR and between cf6d350 and 02f8e48.

📒 Files selected for processing (2)

• src/runtime/cli/init_command.rs
• test/cli/init/init.test.ts

Walkthrough

Changes

React dependencies for bun init

Layer / File(s)	Summary
Detect and add React dependencies src/runtime/cli/init_command.rs	Non-minimal scaffolds detect missing react and @types/react packages. The initializer adds React 19 peer and type dependencies when needed.
Validate generated manifests and scaffolds test/cli/init/init.test.ts, docs/quickstart.mdx	Tests cover generated, reinitialized, blank, existing-dependency, and minimal scaffolds. The quickstart manifest includes the generated React dependencies.

Suggested reviewers: jarred-sumner

🚥 Pre-merge checks | ✅ 4

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly states that the blank scaffold adds React and its type definitions so TSX works.
Description check	✅ Passed	The description includes both required sections and provides clear implementation details and verification results.
Linked Issues check	✅ Passed	The changes address issue #5056 by enabling TSX execution and type-checking while preserving existing dependencies and minimal scaffolds.
Out of Scope Changes check	✅ Passed	The documentation, implementation, and tests directly support the scaffold React dependency objective.

---

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@test/cli/init/init.test.ts`:
- Around line 303-315: Update the initializer subprocess test around Bun.spawn
to concurrently drain stdout and stderr while awaiting proc.exited, then assert
the combined subprocess result after the package manifest expectations. Ensure
the test fails when bun init exits unsuccessfully, while preserving the existing
dependency assertions.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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📒 Files selected for processing (3)

• docs/quickstart.mdx
• src/runtime/cli/init_command.rs
• test/cli/init/init.test.ts

[robobun]

^{Updated 11:20 PM PT - Jul 31st, 2026}

✅ @robobun, your commit 02f8e48368385ccfdb46d5ccea5044ecd8784a71 passed in Build #86601! 🎉

---

🧪   To try this PR locally:

bunx bun-pr 36607

That installs a local version of the PR into your bun-36607 executable, so you can run:

bun-36607 --bun

[claude]

Both earlier findings are addressed — needs_react_dependency is now gated on Template::Blank so the Library template stays react-free, and the existing-react test drains its pipes and asserts exit. The code looks correct to me. Deferring to a maintainer only because making react + @types/react part of the default bun init -y scaffold is a user-facing default change worth a human sign-off.

What was reviewed:

• needs_react_dependency gating: --minimal, TypescriptLibrary, React templates (early-return), and existing-react-in-any-dep-bucket all skip; only Template::Blank adds it.
• peerDependencies block still writes typescript independently when needs_react_dependency is false.
• New tests drain stdout/stderr concurrently; --minimal test now pins devDependencies to exactly @types/bun.

Extended reasoning...

Overview

The PR adds react (peer) and @types/react (dev) to the bun init -y blank scaffold so a .tsx file resolves react/jsx-runtime out of the box, matching the tsconfig's existing "jsx": "react-jsx". Touches src/runtime/cli/init_command.rs (~40 lines), test/cli/init/init.test.ts (two new tests + snapshot updates + tightened --minimal assertions), and docs/quickstart.mdx.

Prior feedback

I previously flagged (1) the react gate leaking into Template::TypescriptLibrary (a publishable, non-private scaffold) and (2) an undrained-pipe subprocess test. Commit 02f8e48 gates on template == Template::Blank, and 768876c drains and asserts exit in the existing-react test. Both are resolved in the current diff.

Security risks

None. Scaffold-time dependency-list edits; no untrusted-input parsing, no auth/crypto/permissions.

Level of scrutiny

Code-wise this is low risk — it mirrors the existing needs_typescript_dependency pattern line-for-line, and the Template::Blank gate plus the three-bucket presence check keep it from clobbering existing setups or leaking into other templates. Tests cover blank, existing-react, and --minimal.

Why defer rather than approve

This changes what every bun init -y produces: react and @types/react are now installed by default in the blank template. That is a product/UX default (linked to #5056) rather than a pure bugfix, and per the approval guidelines a human should weigh in on user-facing default changes of this kind. No code concerns remain from my side.