世人もすなるM1　Mac移行といふものを、吾もしてみむとてするなり。

担当しているrubyのプロジェクトで、そろそろM1　Macで開発できるようにしましょうとなり、移行作業しました。
bundle install は問題ありませんでしたが、rspecを実行しようとしたら、次のようなエラーがでました。

LoadError:
  dlopen(/Users/astronoka/.rbenv/versions/2.7.6/lib/ruby/gems/2.7.0/gems/mysql2-0.5.3/lib/mysql2/mysql2.bundle, 0x0009): symbol not found in flat namespace '_mysql_affected_rows' - /Users/astronoka/.rbenv/versions/2.7.6/lib/ruby/gems/2.7.0/gems/mysql2-0.5.3/lib/mysql2/mysql2.bundle

関数シンボルが見つからず、、、、gem mysql2が正しくビルドできてないみたい。。。

brewでmysql-clientを入れたけど、ちゃんとlibが認識されていないのかも

$ brew info mysql-client
mysql-client: stable 8.0.29 (bottled) [keg-only]
Open source relational database management system
https://dev.mysql.com/doc/refman/8.0/en/
/opt/homebrew/Cellar/mysql-client/8.0.29 (129 files, 149.0MB)
  Poured from bottle on 2022-06-03 at 01:29:22
From: https://github.com/Homebrew/homebrew-core/blob/HEAD/Formula/mysql-client.rb
License: GPL-2.0-only with Universal-FOSS-exception-1.0
==> Dependencies
Build: cmake ✘, pkg-config ✔
Required: libevent ✔, libfido2 ✔, openssl@1.1 ✔, zstd ✔
==> Caveats
mysql-client is keg-only, which means it was not symlinked into /opt/homebrew,
because it conflicts with mysql (which contains client libraries).

If you need to have mysql-client first in your PATH, run:
  echo 'export PATH="/opt/homebrew/opt/mysql-client/bin:$PATH"' >> /Users/astronoka/.bash_profile

For compilers to find mysql-client you may need to set:
  export LDFLAGS="-L/opt/homebrew/opt/mysql-client/lib"
  export CPPFLAGS="-I/opt/homebrew/opt/mysql-client/include"

For pkg-config to find mysql-client you may need to set:
  export PKG_CONFIG_PATH="/opt/homebrew/opt/mysql-client/lib/pkgconfig"

==> Analytics
install: 38,774 (30 days), 85,297 (90 days), 310,430 (365 days)
install-on-request: 33,324 (30 days), 72,951 (90 days), 271,068 (365 days)
build-error: 99 (30 days)

よく見たらLDFLAGSと、CPPFLAGSの指定があったので　bundle configで設定してみる。
（brew bundle している間はDiablo Immortalやってました。。）

bundle config build.mysql2 "--with-ldflags=-L/opt/homebrew/opt/mysql-client/lib --with-cppflags=-I/opt/homebrew/opt/mysql-client/include"

この状態で mysql2 を再インストールしたら動きました 🙌

追伸：

brew で　インストールした mysql-clientにも mysql_config が存在していました。

$ /opt/homebrew/opt/mysql-client/bin/mysql_config
Usage: /opt/homebrew/opt/mysql-client/bin/mysql_config [OPTIONS]
Compiler: AppleClang 13.1.6.13160021
Options:
        --cflags         [-I/opt/homebrew/opt/mysql-client/include/mysql ]
        --cxxflags       [-I/opt/homebrew/opt/mysql-client/include/mysql ]
        --include        [-I/opt/homebrew/opt/mysql-client/include/mysql]
        --libs           [-L/opt/homebrew/opt/mysql-client/lib -lmysqlclient -lz -L/opt/homebrew/lib -lzstd -L/opt/homebrew/opt/openssl@1.1/lib -lssl -lcrypto -lresolv]
        --libs_r         [-L/opt/homebrew/opt/mysql-client/lib -lmysqlclient -lz -L/opt/homebrew/lib -lzstd -L/opt/homebrew/opt/openssl@1.1/lib -lssl -lcrypto -lresolv]
        --plugindir      [/opt/homebrew/Cellar/mysql-client/8.0.29/lib/plugin]
        --socket         [/tmp/mysql.sock]
        --port           [0]
        --version        [8.0.29]
        --variable=VAR   VAR is one of:
                pkgincludedir [/opt/homebrew/opt/mysql-client/include/mysql]
                pkglibdir     [/opt/homebrew/opt/mysql-client/lib]
                plugindir     [/opt/homebrew/Cellar/mysql-client/8.0.29/lib/plugin]

指定するオプションは --with-mysql-config だけでよいのかもしれません(未確認)