Python 3

To see a summary of our current position on Python 3 support, see SupportedPythonVersions#Python_3.x_support.

This is a status page for keeping track of what needs to be done to make progress on Mercurial on Python 3.

GregorySzorc, AugieFackler, YuyaNishihara and PulkitGoyal are some of those who are responsible for the work done until now. PulkitGoyal was selected as GSoC student to do the porting work with MartijnPieters as his mentor.

1. What Works

run-tests.py can pass its own tests (test-run-tests.py and test-run-tests.t) under 2.6, 2.7 and 3.5.

2. Next Steps

• Eliminate all Python 3 compatibility warnings from test-check-py3-compat.t

• Get the entire codebase working with 'from future import absolute_import' (Exceptions Left)

  • This requires fixing some cyclic imports. See test-check-module-imports.t for currently whitelisted cyclic imports.

• Make existing modules at least parse with Python 3 (still some Python 2.x syntax)

• Remove 2to3 and have the source be 2.6/2.7/3.5 compatible

• Conditionalize imports for renamed modules

• Get the C extensions compiling correctly in Python 3
• The codebase uses a source transformer which converts every string to bytes and few other hacks which are required to port. There are places where unicode is required in both Python 2 and 3, there are places where unicode is required in Python 3, and bytes in Python 2. So these things are to be fixed.