Improve error message when .python-version contains invisible characters
#354
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…cters In Honeycomb metrics for the classic buildpack, there are a number of failures due to stray ASCII control codes or invisible Unicode characters being present before/after the version in `.python-version`. For example, I've seen the ASCII `ESC` control code (`U+001B`) and the Unicode zero width no-break space (`U+FEFF`). (I also checked the pyenv and uv `.python-version` parsing implementations, and they don't support these stray characters either.) Being invisible, these don't show up in the error message to users, which makes understanding and resolving the issue harder. Now, such characters are replaced by the `�` symbol. See also: - https://ui.honeycomb.io/heroku/datasets/builds/board-query/DwMoerdz3jj/result/ovg8DxtftcC?vs=hideCompare - https://www.ascii-code.com/ - https://invisible-characters.com/ - https://doc.rust-lang.org/std/primitive.str.html#method.replace - https://doc.rust-lang.org/std/primitive.char.html#method.is_ascii - https://doc.rust-lang.org/std/primitive.char.html#method.is_ascii_control - https://github.com/pyenv/pyenv/blob/master/libexec/pyenv-version-file-read - https://github.com/astral-sh/uv/blob/0.6.16/crates/uv-python/src/version_files.rs#L155-L180 GUS-W-18225365.
colincasey
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Apr 24, 2025
Malax
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Apr 24, 2025
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## heroku/python ### Removed - Removed support for the deprecated `runtime.txt` file. Python versions must now be specified using a `.python-version` file instead. ([#352](#352)) - Removed support for Ubuntu 20.04 (and thus Heroku-20 / `heroku/builder:20`). ([#358](#358)) ### Changed - Improved the error messages shown when `.python-version` contains an invalid Python version or stray invisible characters (such as ASCII control codes). ([#353](#353) and [#354](#354)) - Improved the error messages shown if I/O errors occur. ([#355](#355) and [#356](#356))
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## heroku/python ### Removed - Removed support for the deprecated `runtime.txt` file. Python versions must now be specified using a `.python-version` file instead. ([#352](heroku/buildpacks-python#352)) - Removed support for Ubuntu 20.04 (and thus Heroku-20 / `heroku/builder:20`). ([#358](heroku/buildpacks-python#358)) ### Changed - Improved the error messages shown when `.python-version` contains an invalid Python version or stray invisible characters (such as ASCII control codes). ([#353](heroku/buildpacks-python#353) and [#354](heroku/buildpacks-python#354)) - Improved the error messages shown if I/O errors occur. ([#355](heroku/buildpacks-python#355) and [#356](heroku/buildpacks-python#356))
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Backports the improvements made as part of: - heroku/buildpacks-python#352 - heroku/buildpacks-python#353 - heroku/buildpacks-python#354 - heroku/buildpacks-python#355 Plus: - applies similar changes to equivalent error messages that only exist in the classic buildpack (eg the Pipenv errors) - switches to use of contractions as per the CX team's style guidelines GUS-W-18225347. GUS-W-18421778.
edmorley
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Backports the error message/build output improvements made as part of: - heroku/buildpacks-python#352 - heroku/buildpacks-python#353 - heroku/buildpacks-python#354 - heroku/buildpacks-python#355 Plus: - applies similar changes to equivalent error messages that only exist in the classic buildpack (eg the Pipenv errors) - switches to use of contractions as per the CX team's style guidelines GUS-W-18225347. GUS-W-18421778.
edmorley
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May 2, 2025
Backports the error message/build output improvements made as part of: - heroku/buildpacks-python#352 - heroku/buildpacks-python#353 - heroku/buildpacks-python#354 - heroku/buildpacks-python#355 Plus: - applies similar changes to equivalent error messages that only exist in the classic buildpack (eg the Pipenv errors) - switches to use of contractions as per the CX team's style guidelines GUS-W-18225347. GUS-W-18421778.
edmorley
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May 2, 2025
Backports the error message/build output improvements made as part of: - heroku/buildpacks-python#352 - heroku/buildpacks-python#353 - heroku/buildpacks-python#354 - heroku/buildpacks-python#355 Plus: - applies similar changes to equivalent error messages that only exist in the classic buildpack (eg the Pipenv errors) - switches to use of contractions as per the CX team's style guidelines GUS-W-18225347. GUS-W-18421778.
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In Honeycomb metrics for the classic buildpack, there are a number of failures due to stray ASCII control codes or invisible Unicode characters being present before/after the version in
.python-version.For example, usage of the ASCII
ESCcontrol code (U+001B) and the Unicode zero width no-break space (U+FEFF) as leading/trailing characters alongside the Python version number.Being invisible, these don't show up in the error message to users, which makes understanding and resolving the issue harder.
Now, such characters are replaced by the
�symbol.(I also checked the pyenv and uv
.python-versionparsing implementations, and they don't support these stray characters either.)See also:
GUS-W-18225365.