sql(mysql): add foundRows option to opt into CLIENT_FOUND_ROWS

[robobun]

Fixes #30843.

Repro

import { SQL } from "bun";
const sql = new SQL({ adapter: "mysql", /* ... */ });
await sql`create table t (id int primary key, v int not null)`;
await sql`insert into t values (1, 10)`;

// UPDATE matches one row but changes no column value:
const { affectedRows } = await sql`update t set v = v where id = 1`;
// Bun 1.3.14:  affectedRows = 0  ← indistinguishable from "matched no rows"
// mysql2:      affectedRows = 1  (default)
// mariadb:     affectedRows = 1  (default)

Cause

Capabilities::get_default_capabilities in src/sql/mysql/Capabilities.rs
never set CLIENT_FOUND_ROWS, and there was no user-facing option to opt
in. The MySQL server's OK_Packet.affected_rows therefore carried
changed-rows counts, not matched-rows counts.

mysql2 enables CLIENT_FOUND_ROWS by default (opt-out via
flags: ["-FOUND_ROWS"]) and mariadb does the same (opt-out via
foundRows: false). Code migrated from either driver silently lost the
ability to tell "matched but unchanged" from "didn't match" apart.

Fix

Add a foundRows connection option (accepted on the options object and
as a ?foundRows=... URL query param). Default is true, matching the
mysql2 / mariadb defaults. When enabled, the client OR-s
CLIENT_FOUND_ROWS into the capability set it requests during the
HandshakeResponse41, so subsequent affected_rows counts come back with
matched-rows semantics.

new SQL({ adapter: "mysql", /* ... */ });                    // foundRows: true (default)
new SQL({ adapter: "mysql", foundRows: false, /* ... */ });  // server's changed-rows semantics
new SQL("mysql://root@127.0.0.1/test?foundRows=false");       // URL form (options object wins)

The option is threaded through:
parseOptions → createMySQLConnection call → JSMySQLConnection::create_instance → MySQLConnection::init → MySQLConnection.found_rows field → handle_handshake's requested.CLIENT_FOUND_ROWS.

parseOptions also writes foundRows into the DefinedOptions
structure for Postgres/SQLite adapters — they ignore it, so the option
is MySQL-only without any adapter switch in the parser.

Verification

New test: test/js/sql/sql-mysql-found-rows.test.ts uses a minimal mock
MySQL server (no Docker required) to inspect the client's
HandshakeResponse41 capability_flags bit 1 (CLIENT_FOUND_ROWS):

Case	Bit 1
default (no foundRows)	set ✓
foundRows: true	set ✓
foundRows: false	cleared ✓
URL ?foundRows=false	cleared ✓
options foundRows: true + URL ?foundRows=false	set (options win) ✓
server round-trip affectedRows: 1 reaches JS	✓

Fail-before:

$ USE_SYSTEM_BUN=1 bun test test/js/sql/sql-mysql-found-rows.test.ts
 3 pass
 3 fail     ← the three that exercise the new behavior

Pass-after:

$ bun bd test test/js/sql/sql-mysql-found-rows.test.ts
 6 pass
 0 fail

Existing MySQL tests (sql-mysql-auth-short-nonce, 28004,
adapter-env-var-precedence, adapter-override, sql-mysql-cached-error,
sql-mysql-bind-oob, sql-mysql-bind-blob-borrow,
sql-mysql-raw-length-prefix, sql-mysql-columns-realloc-oom,
sql-mysql-clean-reentry) still pass.

Extra commit: build fix

build: JSON-stringify OVERLAY_CSS define value in bake-codegen — wraps
the raw minified CSS in JSON.stringify so the pre-auto-quote bootstrap
bun (1.3.13, used in the CI Dockerfile) can parse define: values that
start with *{...}. Independent of the MySQL change; needed for cold
builds.

Rebase notes

Rebased onto 0b20408b65 (Hardening: input validation and bounds tightening
across 26 subsystems, #31129), which added allowPublicKeyRetrieval to the
same MySQL connection plumbing I was touching for foundRows. Resolved by
keeping both parameters side-by-side:

• packages/bun-types/sql.d.ts — both JSDoc blocks retained, in order
  allowPublicKeyRetrieval then foundRows.
• src/js/internal/sql/mysql.ts — createMySQLConnection arg list is
  ...!prepare, !!allowPublicKeyRetrieval, !!foundRows.
• src/sql_jsc/mysql/JSMySQLConnection.rs — callframe.argument(15) reads
  allow_public_key_retrieval, argument(16) reads found_rows.
• src/sql_jsc/mysql/MySQLConnection.rs — init signature ends with
  allow_public_key_retrieval, found_rows.

All 7 sql-mysql-found-rows.test.ts cases still pass after the rebase.

[robobun]

^{Updated 4:30 AM PT - May 21st, 2026}

❌ @autofix-ci[bot], your commit 5e65cda has some failures in Build #56606 (All Failures)

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Walkthrough

This PR adds a foundRows boolean option to Bun.SQL's MySQL adapter, enabling CLIENT_FOUND_ROWS capability negotiation during handshake. When enabled, affected_rows values match mysql2/mariadb semantics (matched rows). The option defaults to true and can be set via connection options or URL query string.

Changes

MySQL foundRows feature

Layer / File(s)	Summary
Public type contract packages/bun-types/sql.d.ts	Adds foundRows?: boolean | undefined to the public PostgresOrMySQLOptions interface with documentation describing MySQL CLIENT_FOUND_ROWS semantics and default behavior.
Option parsing and normalization src/js/internal/sql/shared.ts	Parses foundRows from URL query strings (case-insensitive, treating "false"/"0" as disabled) and from the options object, with options-object values overriding URL query strings. Stores normalized boolean in returned options.
Internal type definitions src/js/private.d.ts	Updates DefinedPostgresOrMySQLOptions to include "foundRows" in the set of keys allowed to be "defined" during type configuration.
MySQL binding (TypeScript/Zig interface) src/js/internal/sql/mysql.ts	Updates MySQLDotZig.createConnection signature to accept foundRows: boolean, destructures it from pooled connection options with default true, and forwards it to underlying createMySQLConnection call.
MySQL protocol layer (Rust/FFI) src/sql_jsc/mysql/JSMySQLConnection.rs, src/sql_jsc/mysql/MySQLConnection.rs	Extracts found_rows from JS FFI argument, passes it through MySQLConnection::init, stores it as a connection field, and uses it to control CLIENT_FOUND_ROWS capability negotiation during handshake. Capability negotiation now computes requested flags, conditionally sets CLIENT_FOUND_ROWS based on found_rows, then intersects with server capabilities.
Test coverage for foundRows behavior test/js/sql/sql-mysql-found-rows.test.ts	Implements a mock MySQL server with wire-protocol helpers and test harness that captures negotiated capability flags. Tests verify: default configuration enables CLIENT_FOUND_ROWS, explicit true/false options, URL query string ?foundRows=false, options-over-URL precedence, and that result.affectedRows forwards the server's OK_Packet.affected_rows value.
Codegen define quoting src/codegen/bake-codegen.ts	Wraps OVERLAY_CSS define value with JSON.stringify(...) when calling Bun.build, adding comments about Bun's JSON parsing of define values and compatibility with older Bun versions.
Formatting and cfg-attribute rewrites src/crash_handler/lib.rs, src/errno/lib.rs, src/perf/tracy.rs, src/runtime/..., src/spawn/..., src/spawn_sys/..., src/runtime/jsc_hooks.rs, src/runtime/webview/ChromeProcess.rs	Non-functional reformatting of #[cfg]/#[cfg_attr] attributes and minor expression rewrapping across multiple Rust files; no behavioral changes.

Suggested reviewers:

• alii

🚥 Pre-merge checks | ✅ 4

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately describes the primary change: adding a foundRows option to MySQL connections for CLIENT_FOUND_ROWS capability.
Linked Issues check	✅ Passed	The PR implementation fully satisfies issue #30843 requirements: adds foundRows option defaulting to true, supports URL query parameters with options precedence, threads capability through handshake, provides comprehensive test coverage, and maintains backward compatibility.
Out of Scope Changes check	✅ Passed	All changes are in-scope: MySQL foundRows feature changes, associated TypeScript type updates, and formatting improvements for cfg attributes. The unrelated build fix (bake-codegen OVERLAY_CSS) is explicitly noted as independent.
Description check	✅ Passed	The PR description provides comprehensive coverage of what the PR does, how changes were verified, includes a detailed explanation of the cause and fix, and demonstrates verification through test results.

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[claude]

I didn't find any bugs, but this changes the default affectedRows semantics for all existing Bun MySQL users (now matched-rows instead of changed-rows) — that's a product decision worth a human sign-off, and there's also a CI build failure on x64-baseline.

Extended reasoning...

Overview

This PR adds a foundRows connection option to Bun.SQL's MySQL adapter that controls the CLIENT_FOUND_ROWS capability flag during handshake, threaded from the public TypeScript API (sql.d.ts, shared.ts, mysql.ts, private.d.ts) through the Rust FFI layer (JSMySQLConnection.rs) into the protocol handshake (MySQLConnection.rs). It ships with a self-contained mock-server test (sql-mysql-found-rows.test.ts). It also bundles two unrelated changes: a JSON.stringify wrap for the OVERLAY_CSS define in bake-codegen.ts (cold-build fix), and ~10 Rust files of pure cargo fmt whitespace from the autofix.ci commit.

Security risks

None identified. The new option is a boolean that toggles a single capability bit; URL query parsing is case-insensitive string comparison with no injection surface; the null-byte / protocol-injection guards on connection strings are unchanged.

Level of scrutiny

Medium-high. The mechanical plumbing is straightforward and the capability-bit change in handle_handshake is minimal and correctly placed before intersect(). However, the key judgment call is that foundRows defaults to true, which silently flips affectedRows semantics for every existing Bun MySQL user from changed-rows to matched-rows. The PR argues this matches mysql2/mariadb defaults (true), but it's still a behavioral break for anyone already on Bun's MySQL adapter — that's a product/compat decision a maintainer should explicitly endorse rather than have auto-approved.

Other factors

• robobun reports a build failure on x64-baseline - build-rust for the latest commit, which should be resolved or explained before merge.
• The PR mixes three concerns (feature + unrelated build fix + autofix formatting); fine if that's the project norm, but worth a human glance.
• Test coverage for the new option is solid (6 cases including URL vs. options precedence and OK_Packet round-trip).

[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 `@packages/bun-types/sql.d.ts`:
- Around line 383-387: Update the JSDoc for the foundRows option (the comment
block around foundRows in packages/bun-types/sql.d.ts) to remove "MySQL only"
and explicitly state it applies to both MySQL and MariaDB protocols/adapters;
mention that when enabled the driver reports rows matched by the WHERE clause in
affectedRows and that this matches the default behavior of the mysql2 and
mariadb drivers so adapter: "mariadb" is supported.

🪄 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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📥 Commits

Reviewing files that changed from the base of the PR and between 14aa0cf and 345720f.

📒 Files selected for processing (18)

• packages/bun-types/sql.d.ts
• src/codegen/bake-codegen.ts
• src/crash_handler/lib.rs
• src/errno/lib.rs
• src/js/internal/sql/mysql.ts
• src/js/internal/sql/shared.ts
• src/js/private.d.ts
• src/perf/tracy.rs
• src/runtime/cli/Arguments.rs
• src/runtime/cli/run_command.rs
• src/runtime/cli/upgrade_command.rs
• src/runtime/jsc_hooks.rs
• src/runtime/webview/ChromeProcess.rs
• src/spawn/process.rs
• src/spawn_sys/spawn_process.rs
• src/sql_jsc/mysql/JSMySQLConnection.rs
• src/sql_jsc/mysql/MySQLConnection.rs
• test/js/sql/sql-mysql-found-rows.test.ts

[claude]

Thanks for addressing all the nits — the code looks good to me. I'm not auto-approving only because this flips the default affectedRows semantics for existing MySQL users (changed-rows → matched-rows), which is a product call worth a maintainer's explicit sign-off; the musl build failures in CI are also worth a glance before merge.

Extended reasoning...

Overview

This PR adds a foundRows connection option to Bun.SQL's MySQL/MariaDB adapter, threading it from parseOptions() (TS) → createMySQLConnection (TS binding) → JSMySQLConnection::create_instance (Rust FFI) → MySQLConnection.found_rows field → handle_handshake's CLIENT_FOUND_ROWS capability bit. It defaults to true, matching the mysql2/mariadb driver defaults. The PR also bundles an unrelated cold-build fix in bake-codegen.ts (wrap OVERLAY_CSS in JSON.stringify) and ~10 Rust files of purely cosmetic #[cfg(...)] attribute reformatting from autofix.ci. A new mock-MySQL-server test file (7 cases) and a docs section in runtime/sql.mdx round it out.

All three of my earlier inline nits (duplicate "max" in the type union, String() coercion for duplicate URL query keys, and the missing sql.mdx docs section) have been addressed and resolved.

Security risks

None identified. The option is a boolean that toggles a single well-defined MySQL capability flag during the handshake; no user-controlled data flows into protocol bytes beyond that. URL query parsing coerces through String() before .toLowerCase(), avoiding the array-method TypeError on duplicate keys.

Level of scrutiny

Moderate-to-high. The implementation is small, well-isolated, and well-tested, but two things push this above the auto-approve bar:

1. Default behavior change. Setting foundRows: true by default flips affectedRows semantics for every existing Bun MySQL user from changed-rows to matched-rows. Code that relied on affectedRows === 0 to mean "no column values changed" will silently behave differently. The PR description and docs are clear about this and the rationale (ecosystem alignment) is sound, but choosing to ship a default flip vs. an opt-in is a product decision a maintainer should explicitly sign off on.
2. Wire-protocol path. The Rust change in MySQLConnection::handle_handshake restructures capability negotiation slightly (compute → set bit → intersect). It's correct on inspection, but handshake code is load-bearing.

Other factors

• CI (Build #54959) shows build failures on three musl targets (x64-musl, x64-musl-baseline, aarch64-musl). These may be infrastructure-related and unrelated to this change, but should be confirmed green before merge.
• The bundled bake-codegen.ts fix is independent of the MySQL change (acknowledged in the PR description).
• Test coverage for the new option is thorough (default, explicit true/false, URL form, options-over-URL precedence, duplicate-key URL, and affectedRows round-trip via mock server).

[claude]

All prior nits are addressed and I didn't find any bugs, but this changes the default affectedRows semantics for existing MySQL users and threads a new arg through the Rust handshake path — worth a human sign-off on the default flip.

Extended reasoning...

Overview

Adds a foundRows connection option (default true) for the MySQL/MariaDB adapter that toggles CLIENT_FOUND_ROWS in the HandshakeResponse41 capability flags. Threaded through parseOptions (shared.ts) → createMySQLConnection (mysql.ts, positional arg 16) → JSMySQLConnection::create_instance (Rust FFI) → MySQLConnection::init → handle_handshake. Also adds public types, docs in runtime/sql.mdx, a 300-line mock-server test, and an unrelated build fix in bake-codegen.ts.

Security risks

None identified. The option only flips a single capability bit during handshake; no auth, crypto, or input-validation surface changes. The URL query-string parser coerces via String() before .toLowerCase() (fixed after my earlier nit), so no new throw paths on adversarial URLs.

Level of scrutiny

Medium-high. While the implementation is clean, well-tested, and all prior review feedback (mine and CodeRabbit's) has been addressed, this is not a purely additive change — it flips the default affectedRows semantics for every existing Bun MySQL user from changed-rows to matched-rows. That's the right call for mysql2/mariadb compatibility, but it's a behavioral default change to a public API that a maintainer should explicitly approve. It also touches the Rust protocol handshake (MySQLConnection.rs:642-655) and adds a positional FFI argument (callframe.argument(16)), which sits adjacent to the recently-rebased allowPublicKeyRetrieval plumbing.

Other factors

• All four prior inline comments (3 from me, 1 from CodeRabbit) are resolved with follow-up commits.
• Bundles an unrelated bake-codegen.ts build fix (JSON.stringify wrap for OVERLAY_CSS) — reasonable but worth a glance.
• Test coverage is solid (mock server inspects the actual capability bit on the wire, plus precedence and duplicate-key cases).