Fix crash in Bun.build with many conditions

[robobun]

What does this PR do?

Fixes an operator precedence bug in ESMConditions.init that caused a debug assertion failure (and potential memory corruption in release) when passing several conditions to Bun.build().

The expression:

defaults.len + 2 + if (allow_addons) 1 else 0 + conditions.len

parses as:

defaults.len + 2 + (if (allow_addons) 1 else (0 + conditions.len))

So when allow_addons is true (the default), conditions.len is dropped from the reserved capacity and subsequent putAssumeCapacity calls overflow the map.

How did you verify your code works?

Added a regression test that passes 10 conditions to Bun.build(). Before this fix it triggers reached unreachable code in MultiArrayList.addOneAssumeCapacity; after the fix it builds successfully.

Found by Fuzzilli (fingerprint fdba7e39f969672c).

[robobun]

^{Updated 1:09 PM PT - May 11th, 2026}

❌ @robobun, your commit 0c7a84d has 1 failures in Build #53446 (All Failures):

• scripts/build/ci.ts - build failed on 🐧 x64-musl - build-zig
• scripts/build/ci.ts - build failed on 🐧 aarch64-android - build-zig
• scripts/build/ci.ts - build failed on 🍎 aarch64 - build-zig
• scripts/build/ci.ts - build failed on :freebsd: aarch64 - build-zig
• scripts/build/ci.ts - build failed on 🐧 x64-baseline - build-zig
• scripts/build/ci.ts - build failed on 🐧 x64-musl-baseline - build-zig
• scripts/build/ci.ts - build failed on :freebsd: x64 - build-zig
• scripts/build/ci.ts - build failed on 🍎 x64 - build-zig
• scripts/build/ci.ts - build failed on 🐧 aarch64-musl - build-zig
• scripts/build/ci.ts - build failed on 🐧 aarch64 - build-zig
• scripts/build/ci.ts - build failed on 🐧 x64-android - build-zig
• scripts/build/ci.ts - build failed on 🐧 x64 - build-zig

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🧪   To try this PR locally:

bunx bun-pr 30514

That installs a local version of the PR into your bun-30514 executable, so you can run:

bun-30514 --bun

[github-actions]

This PR may be a duplicate of:

1. Fix crash in Bun.build with many conditions #30466 - Also fixes the crash in Bun.build with many conditions by correcting the ESMConditions.init capacity calculation in src/bundler/options.zig

🤖 Generated with Claude Code

[robobun]

Duplicate of #30466.

[coderabbitai]

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📒 Files selected for processing (2)

• src/bundler/options.zig
• test/bundler/bun-build-api.test.ts

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Walkthrough

ESMConditions capacity computation is simplified to use @intFromBool(allow_addons) instead of a conditional expression. A regression test verifies the build succeeds with multiple conditions.

Changes

Bundler Conditions Capacity Fix

Layer / File(s)	Summary
ESMConditions Capacity Simplification src/bundler/options.zig	Capacity computation for condition maps uses @intFromBool(allow_addons) instead of if (allow_addons) 1 else 0.
Many Conditions Regression Test test/bundler/bun-build-api.test.ts	Concurrent test verifies build succeeds when provided ten custom conditions (c1–c10).

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