[version内容]
ProductName: Mac OS X
ProductVersion: 10.15.2
BuildVersion: 19C57
mysql Ver 8.0.19 for osx10.15 on x86_64 (Homebrew)
Rails version: 6.0.2.1
Ruby version: ruby 2.6.3p62 (2019-04-16 revision 67580) [x86_64-darwin19]

まず、rails appの作成

rails new sample -d mysql

すると、すかさずエラーが！！

An error occurred while installing mysql2 (0.5.3), and Bundler cannot
continue.
Make sure that `gem install mysql2 -v '0.5.3' --source 'https://rubygems.org/'`
succeeds before bundling.
In Gemfile:
 mysql2
     run bundle binstubs bundler
Could not find gem 'rails (~> 6.0.2, >= 6.0.2.1)' in any of the gem sources
listed in your Gemfile.
     run bundle exec spring binstub --all
bundler: command not found: spring
Install missing gem executables with `bundle install`
    rails webpacker:install
Could not find gem 'rails (~> 6.0.2, >= 6.0.2.1)' in any of the gem sources listed in your Gemfile.
Run `bundle install` to install missing gems.

と表示されたため、

gem install mysql2 -v '0.5.3' --source 'https://rubygems.org/'

を実行すると、さらにエラーが

ERROR: While executing gem ... (Errno::EACCES)
  Permission denied @ rb_sysopen - /Users/PC名/.rbenv/versions/2.6.3/lib/ruby/gems/2.6.0/gems/mysql2-0.5.3/CHANGELOG.md

と表示されたため、

sudo gem install mysql2 -v '0.5.3' --source 'https://rubygems.org/'

を実行してみる

bundle install

を実行し

cd sample
rails s

してみると、エラー

Could not find gem 'rails (~> 6.0.2, >= 6.0.2.1)' in any of the gem sources listed in your Gemfile.
Run `bundle install` to install missing gems.

では

Bundle install

してみると、エラー

ERROR: While executing gem ... (Errno::EACCES)
  Permission denied @ rb_sysopen - /Users/PC名/.rbenv/versions/2.6.3/lib/ruby/gems/2.6.0/gems/mysql2-0.5.3/CHANGELOG.md

と表示される

sudo gem install mysql2 -v '0.5.3' --source 'https://rubygems.org/'

してみると

ERROR: Error installing mysql2:
	ERROR: Failed to build gem native extension.
  current directory: /Users/PC名/.rbenv/versions/2.6.3/lib/ruby/gems/2.6.0/gems/mysql2-0.5.3/ext/mysql2
/Users/PC名/.rbenv/versions/2.6.3/bin/ruby -I /Users/PC名/.rbenv/versions/2.6.3/lib/ruby/2.6.0 -r ./siteconf20200301-31071-1cavam6.rb extconf.rb
checking for rb_absint_size()... yes
checking for rb_absint_singlebit_p()... yes
checking for rb_wait_for_single_fd()... yes
Using mysql_config at /usr/local/bin/mysql_config
checking for mysql.h... yes
checking for errmsg.h... yes
checking for SSL_MODE_DISABLED in mysql.h... yes
checking for SSL_MODE_PREFERRED in mysql.h... yes
checking for SSL_MODE_REQUIRED in mysql.h... yes
checking for SSL_MODE_VERIFY_CA in mysql.h... yes
checking for SSL_MODE_VERIFY_IDENTITY in mysql.h... yes
checking for MYSQL.net.vio in mysql.h... yes
checking for MYSQL.net.pvio in mysql.h... no
checking for MYSQL_ENABLE_CLEARTEXT_PLUGIN in mysql.h... yes
checking for SERVER_QUERY_NO_GOOD_INDEX_USED in mysql.h... yes
checking for SERVER_QUERY_NO_INDEX_USED in mysql.h... yes
checking for SERVER_QUERY_WAS_SLOW in mysql.h... yes
checking for MYSQL_OPTION_MULTI_STATEMENTS_ON in mysql.h... yes
checking for MYSQL_OPTION_MULTI_STATEMENTS_OFF in mysql.h... yes
checking for my_bool in mysql.h... no
-----
Don't know how to set rpath on your system, if MySQL libraries are not in path mysql2 may not load
-----
-----
Setting libpath to /usr/local/Cellar/mysql/8.0.19/lib
-----
creating Makefile

current directory: /Users/PC名/.rbenv/versions/2.6.3/lib/ruby/gems/2.6.0/gems/mysql2-0.5.3/ext/mysql2
make "DESTDIR=" clean

current directory: /Users/PC名/.rbenv/versions/2.6.3/lib/ruby/gems/2.6.0/gems/mysql2-0.5.3/ext/mysql2
make "DESTDIR="
compiling client.c
compiling infile.c
compiling mysql2_ext.c
compiling result.c
compiling statement.c
linking shared-object mysql2/mysql2.bundle
ld: library not found for -lssl
clang: error: linker command failed with exit code 1 (use -v to see invocation)
make: *** [mysql2.bundle] Error 1

make failed, exit code 2

Gem files will remain installed in /Users/PC名/.rbenv/versions/2.6.3/lib/ruby/gems/2.6.0/gems/mysql2-0.5.3 for inspection.
Results logged to /Users/PC名/.rbenv/versions/2.6.3/lib/ruby/gems/2.6.0/extensions/x86_64-darwin-19/2.6.0-static/mysql2-0.5.3/gem_make.out

と初心者には厳しい、エラーの嵐

なので

gem install mysql2 -v '0.5.3' --source 'https://rubygems.org/'`

を実行するも

ERROR: While executing gem ... (Errno::EACCES)
  Permission denied @ rb_sysopen - /Users/PC名/.rbenv/versions/2.6.3/lib/ruby/gems/2.6.0/gems/mysql2-0.5.3/CHANGELOG.md

となったので

sudo gem install mysql2 -v '0.5.3' --source 'https://rubygems.org/'

を実行し

rails s

すると

Could not find gem 'rails (~> 6.0.2, >= 6.0.2.1)' in any of the gem sources listed in your Gemfile.
Run `bundle install` to install missing gems.

と表示。

gemfileにgem ‘rails (~> 6.0.2, >= 6.0.2.1)’

と記載されているがどうすればいいかわからず途方にくれる。

その後、linker command failed with exit code 1と、
mysqlをセットでググる。

というヒントを頂き、
以下の記事を参考にトライするも不可

【Rails】MySQL2がbundle installできない時の対応方法

その後色々試してみて、以下で bundle install可能になりました。

bundle config --local build.mysql2 "--with-ldflags=-L/usr/local/opt/openssl/lib --with-cppflags=-I/usr/local/opt/openssl/include"

実行後

$ bundle install

$ rails s

で(抜粋)以下のようなエラー

configuration.rb:95:in `rescue in load': Webpacker configuration file not found /Users/PC名/Desktop/hello/sample/config/webpacker.yml. Please run rails webpacker:install Error: No such file or directory @ rb_sysopen - /Users/PC名/Desktop/hello/sample/config/webpacker.yml (RuntimeError)

rails webpacker:install

を実行し

【Rails】Rails6 開発時につまづきそうな webpacker, yarn 関係のエラーと解決方法

を参考にインストール

rails webpacker:install

で表示される以下のエラーを検討

Webpacker configuration file not found /Users/PC名/Desktop/hello/sample/config/webpacker.yml. Please run rails webpacker:install Error: No such file or directory @ rb_sysopen - /Users/PC名/Desktop/hello/sample/config/webpacker.yml (RuntimeError)

yarn -v

をすると

-bash: yarn: command not found

と表示される。

brew install yarn

yarn -v

yarn install v1.22.0

を実行し、

rails webpacker:install

rails s

すると

Mysql2::Error::ConnectionError (Can't connect to local MySQL server through socket '/tmp/mysql.sock' (2)):

と表示されたため

Markdown: mysqlが起動できない（Can't connect to local MySQL server through socket '/tmp/mysql.sock' (2)）

を参考に

sudo touch /tmp/mysql.sock
sudo mysql.server restart

とすると

ERROR! MySQL server process #19810 is not running!
Starting MySQL
.. ERROR! The server quit without updating PID file (/usr/local/var/mysql/mbp.local.pid).

となる。それではと

mysqlの起動エラー対応 in mac

を参考に

sudo chmod -R 777 /usr/local/var/mysql/

mysql.server start

実行し

Starting MySQL
.......... ERROR! The server quit without updating PID file (/usr/local/var/mysql/mbp.local.pid).

と表示され、

touch /usr/local/var/mysql/mbp.local.pid
mysql.server start

その後、

Starting MySQL

.rm: /tmp/mysql.sock: Permission denied
2020-03-01T13:13:48.6NZ mysqld_safe Fatal error: Can't remove the socket file:
/tmp/mysql.sock.
Please remove the file manually and start /usr/local/Cellar/mysql/8.0.19/bin/mysqld_safe again;
mysqld daemon not started
 ERROR! The server quit without updating PID file (/usr/local/var/mysql/mbp.local.pid).

となり、

mysqlがどうしても起動しない

を参考に

ls -la /usr/local/var/mysql/mbp.local.pid
ls: /usr/local/var/mysql/mbp.local.pid: No such file or directory

sudo chown _mysql:_mysql /usr/local/var/mysql/mbp.local.pid

usage: chown [-fhnv] [-R [-H | -L | -P]] owner[:group] file ...
    chown [-fhnv] [-R [-H | -L | -P]] :group file ...

mysql.server start

Starting MySQL
... ERROR! The server quit without updating PID file (/usr/local/var/mysql/mbp.local.pid).

と表示されるので

sudo rm -rf /usr/local/var/mysql

brew uninstall mysql

brew install mysql

などトライし

mysql 起動時のThe server quit without updating PID file エラーの回避法

を参考に

touch /usr/local/var/mysql/mbp.local.pid

【8.0.12】mysql2が開けないエラーの解消方法

を参考に

cd /tmp

sudo rm -rf mysql.sock

mysql.server start

Starting MySQL
.. SUCCESS! 
``
となったので

Rails s

すると

ActiveRecord::NoDatabaseError

と表示され

bundle exec rake db:create

Rails s


を行い、完成しました。

ふぅ（´-`）　やっと完了です。

この記事が、同じエラーで困っている方の役にも立てたら幸いです。