[WIP] Fix func pack --build-native-deps failure on Windows for Python 3.13

[Copilot]

Fix for func pack --build-native-deps failing on Windows with Python 3.13+

Problem

The Docker image name azure-functions/python:4-python3.13-buildenv contains a colon (:) which is invalid in Windows file paths. When the code tries to create a temporary directory using this image name, it fails on Windows.

Plan

• Understand the codebase and identify the issue location
• Fix PythonHelpers.cs to sanitize the image name when using it as a directory path
• Add unit tests to verify the fix works on Windows
• Build and test the changes
• Run code review
• Run security checks

Technical Details

The issue is in PythonHelpers.ChoosePythonBuildEnvImage() method where:

• Line 567: image = $"azure-functions/python:4-python{workerInfo.Major}.{workerInfo.Minor}-buildenv"
• Line 570: string tempDockerfileDirecotry = Path.Combine(Path.GetTempPath(), $"{image}-docker")

The fix will replace colons with a safe character (like hyphen) when creating the directory path, while keeping the actual Docker image name unchanged.

Original prompt

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This section details on the original issue you should resolve

<issue_title>func pack --build-native-deps fails for Python 3.13+ when running on Windows</issue_title>
<issue_description>### Version

4.4.0+

Description

Running func pack --build-native-deps for Python 3.13+ on a Windows machine throws an error saying that:

The directory name is invalid. : 'C:\Users\victoriahall\AppData\Local\Temp\azure-functions\python:4-python3.13-buildenv-docker'

I also tested with CT version 4.5.0 and got the same error. This only seems to happen with Windows - Mac seems to work as expected.

Full output:

(.venv313) PS C:\Users\victoriahall\Documents\repos\sdk-servicebus> func pack --build-native-deps
'local.settings.json' found in root directory (C:\Users\victoriahall\Documents\repos\sdk-servicebus).
Resolving worker runtime to 'python'.
'local.settings.json' found in root directory (C:\Users\victoriahall\Documents\repos\sdk-servicebus).
Resolving worker runtime to 'python'.

Validating project...

  Validate host.json: PASSED
  Validate Flag Compatibility: PASSED
  Validate Folder Structure: PASSED
  Validation .python_packages directory exists: WARNING
    Directory '.python_packages' not found or is empty.
  Validate Python Programming Model: PASSED

The directory name is invalid. : 'C:\Users\victoriahall\AppData\Local\Temp\azure-functions\python:4-python3.13-buildenv-docker'
(.venv313) PS C:\Users\victoriahall\Documents\repos\sdk-servicebus> func --version
4.4.0

Steps to reproduce

1. On a Windows machine, download Python 3.13 & create a 3.13 environment
2. Start Docker
3. Run func pack --build-native-deps in the terminal</issue_description>

<agent_instructions>In PythonHelpers, we set the image name to have a : in it, which is also used as the filename for the temp dockerfile. : is not an acceptable file name on windows machines so we should fix this by either removing the : or haveing a different filename to the image name</agent_instructions>

Comments on the Issue (you are @copilot in this section)

@liliankasem Thanks for catching this! The colon is acceptable in osx filepath but not in windows - should be an easy fix to update the filepath for the temp dockerfile. Will make sure to test on a windows machine :)

• Fixes func pack --build-native-deps fails for Python 3.13+ when running on Windows #4740

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