`meson fmt -e` inconsistent formatting when using either stdin or a different working directory

[tmuehlbacher]

Describe the bug

Meson doesn't know the file name when formatting according to editorconfig and
hence cannot correctly deduce the correct config when using stdin.

To Reproduce try meson fmt -e on https://github.com/fwupd/fwupd/tree/2.0.7

There is a difference when using meson fmt with editorconfig enabled between
regular file path and reading from stdin. This seems likely because the stdin
- matches only against [*].

$ editorconfig $(realpath meson.build)
charset=utf-8
end_of_line=lf
indent_size=2
indent_style=space
insert_final_newline=true
max_line_length=100
tab_width=8
trim_trailing_whitespace=true

$ diff -u <(meson fmt -e meson.build) <(meson fmt -e - <meson.build)
...

Using stdin is preferable for use with some editor formatting plugins, at
least for Emacs format-all support. Since this allows for formatting the editor
buffer contents without first writing them to a file.

A solution could possibly require adding a separate argument that allows
supplying a file name just for editorconfig eval but without touching that file
path.

There is also a difference when it comes to the working directory.

$ editorconfig $(realpath data/meson.build)
charset=utf-8
end_of_line=lf
indent_size=2
indent_style=space
insert_final_newline=true
max_line_length=100
tab_width=8
trim_trailing_whitespace=true

$ diff -u <(meson fmt -e data/meson.build) <(cd data; meson fmt -e meson.build)

Here it seems that an editorconfig file in a parent dir is not evaluated.

Expected behavior is that meson fmt has consistent output with the
--editor-config option regardless of using stdin and regardless of current
working directory.

system parameters

• what operating system: NixOS unstable (25.05.20250326.f55926c)
• what Python version are you using: 3.12.9
• what meson --version: 1.7.0

[bruchar1]

I think there are three things here:

• Using stdin, we have no path where to look for .editorconfig
• Using stdin, we have no clue about the analysed file name (we should probably default to meson.build)
• Using relative paths, we do not search for .editorconfig in parents directory (this is a bug!)

First problem could be solved by adding a --editor-config-path argument

Second problem could be solved assuming the filename is meson.build (but this would not allow filtering by directory), or by adding a --source-path argument

[tmuehlbacher]

thanks for looking at this.

a different solution to the first two might be add an argument to specify an assumed file path. there appears to be some precedence for similar arguments when search for buffer-file-name in this file: https://github.com/lassik/emacs-format-all-the-code/blob/fd9c013f5f8094fef99ddabde07d9041737b8454/format-all.el

[bruchar1]

yes! That's exactly what I am figuring. I will submit a PR soon.

[tmuehlbacher]

ah sorry, I missed the last part about --source-path 😅