Wrong path to constraints in requirements-out file

[davisagli]

I'm using mxdev with this configuration:

[settings]
requirements-in = requirements/plone.in
requirements-out = requirements/plone.txt
constraints-out = requirements/constraints.txt
default-target = src
version-overrides =

requirements/plone.in contains:

-c https://dist.plone.org/release/6.0.0b3/constraints.txt
Plone

After I run mxdev, it generates requirements/constraints.txt and requirements/plone.txt, but requirements/plone.txt has the wrong relative path to the constraints file:

###############################################################################
# mxdev combined constraints
-c requirements/constraints.txt

###############################################################################
# begin requirements from: plone.in

Plone

# end requirements from: plone.in
###############################################################################

(It should be -c constraints.txt)

Then that breaks when I try to pip install -r requirements/plone.txt:
ERROR: Could not open requirements file: [Errno 2] No such file or directory: 'requirements/requirements/constraints.txt'

[jensens]

nice catch

[rnixx]

Relates to #25

[gforcada]

I stumbled upon the very same problem 😅

[jensens]

Root Cause Analysis

The issue occurs because mxdev writes the constraints path to the requirements file without calculating the correct relative path.

Location: src/mxdev/processing.py:276

fio.write(f"-c {cfg.out_constraints}\n\n")

Problem: This writes the constraints path exactly as specified in the config file, but pip interprets paths in requirements files relative to the requirements file's directory, not relative to the config file or current working directory.

Example from Issue #22

Config:

[settings]
requirements-out = requirements/plone.txt
constraints-out = requirements/constraints.txt

Current behavior:
The generated requirements/plone.txt contains:

-c requirements/constraints.txt

What pip sees:
When pip processes requirements/plone.txt, it interprets the -c path relative to the requirements file's directory (requirements/), so it looks for:

requirements/requirements/constraints.txt  ❌ Wrong!

Expected behavior:
The generated requirements/plone.txt should contain:

-c constraints.txt

Because both files are in the requirements/ directory, the relative path should just be constraints.txt.

Solution

Calculate the relative path from the requirements-out file's directory to the constraints-out file:

import os
from pathlib import Path

# Calculate relative path from requirements-out directory to constraints-out
req_dir = Path(cfg.out_requirements).parent
const_path = Path(cfg.out_constraints)
relative_const_path = os.path.relpath(const_path, req_dir)

fio.write(f"-c {relative_const_path}\n\n")

This works for all scenarios:

• Same directory: constraints.txt
• Parent directory: ../constraints.txt
• Subdirectory: subdir/constraints.txt
• Different directories: ../other/constraints.txt

Related Issue #25

This fix also addresses issue #25 (support foreign folders for requirements/constraints), as the relative path calculation handles all directory configurations.

---

I will now implement this fix with tests.