By default, pip installs a compiled version of black appropriate for the current architecture. On an ARM Macbook, that ends up with an error message like this:

  File "/Users/stephen/Library/Python/3.12/bin//black", line 5, in <module>
    from black import patched_main
ImportError: dlopen(/Users/stephen/Library/Python/3.12/lib/python/site-packages/black/__init__.cpython-312-darwin.so, 0x0002): tried: '/Users/stephen/Library/Python/3.12/lib/python/site-packages/black/__init__.cpython-312-darwin.so' (mach-o file, but is an incompatible architecture (have 'arm64', need 'x86_64')), '/System/Volumes/Preboot/Cryptexes/OS/Users/stephen/Library/Python/3.12/lib/python/site-packages/black/__init__.cpython-312-darwin.so' (no such file), '/Users/stephen/Library/Python/3.12/lib/python/site-packages/black/__init__.cpython-312-darwin.so' (mach-o file, but is an incompatible architecture (have 'arm64', need 'x86_64'))

The main problem being that we're using the ancient ruby18 bundled with Textmate, which is x86 only. If we allow Python FMT to use system ruby instead, this happens:

/System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/lib/ruby/2.6.0/rubygems/core_ext/kernel_require.rb:54:in `require': dlopen(/Users/stephen/Library/Application Support/TextMate/Managed/Bundles/Bundle Support.tmbundle/Support/shared/lib/osx/plist.bundle, 0x0009): tried: '/Users/stephen/Library/Application Support/TextMate/Managed/Bundles/Bundle Support.tmbundle/Support/shared/lib/osx/plist.bundle' (fat file, but missing compatible architecture (have 'unknown,i386,x86_64', need 'arm64')), '/System/Volumes/Preboot/Cryptexes/OS/Users/stephen/Library/Application Support/TextMate/Managed/Bundles/Bundle Support.tmbundle/Support/shared/lib/osx/plist.bundle' (no such file), '/Users/stephen/Library/Application Support/TextMate/Managed/Bundles/Bundle Support.tmbundle/Support/shared/lib/osx/plist.bundle' (fat file, but missing compatible architecture (have 'unknown,i386,x86_64', need 'arm64')) - /Users/stephen/Library/Application Support/TextMate/Managed/Bundles/Bundle Support.tmbundle/Support/shared/lib/osx/plist.bundle (LoadError)
	from /System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/lib/ruby/2.6.0/rubygems/core_ext/kernel_require.rb:54:in `require'
	from /Users/stephen/Library/Application Support/TextMate/Managed/Bundles/Bundle Support.tmbundle/Support/shared/lib/textmate.rb:5:in `<top (required)>'
	from /System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/lib/ruby/2.6.0/rubygems/core_ext/kernel_require.rb:54:in `require'
	from /System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/lib/ruby/2.6.0/rubygems/core_ext/kernel_require.rb:54:in `require'
	from /Users/stephen/Library/Application Support/TextMate/Bundles/Python-FMT.tmbundle/Support/python_helper.rb:4:in `<top (required)>'
	from /System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/lib/ruby/2.6.0/rubygems/core_ext/kernel_require.rb:54:in `require'
	from /System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/lib/ruby/2.6.0/rubygems/core_ext/kernel_require.rb:54:in `require'
	from Document Will Save:3:in `<main>'

The problem here is that the provided Bundle Support.tmbundle/Support/shared/lib/textmate.rb imports Bundle Support.tmbundle/Support/shared/lib/osx/plist.bundle, which is a compiled ruby extension, distributed by Textmate as a binary for x86_64, i386, and ppc_7400 (!).

Possible solutions to this:

• Make sure to install a source-only version of black (unfortunate and slower)
• Get an MR merged to bundle-support.tmbundle which updates the compiled extensions (ideal, but unlikely given the unfortunate state of Textmate development)
• Manual modification to shared/lib/textmate.rb which comments out the plist import (possibly breaking any plist-parsing ruby-based bundles that happily run in ruby18 with x86-mode?)
• Avoid using TextMate::Process.run() entirely. In this case, maybe textmate2-python-fmt could package a version of the necessary functions which avoids importing plist.bundle