pip wheel of editable requirements creates a .zip file in the wheel directory

[sbidoul]

Environment

• pip version: master branch, today
• Python version: 3.8 (probably irrelevant)
• OS: linux (probably irrelevant)

Description

Consider the following requirements.txt:

-e git+https://github.com/PyPA/packaging@master#egg=packaging

When we run pip wheel -r requirements.txt --wheel-dir=wheelhouse, we now obtain packaging-20.5.dev0.zip in the wheelhouse directory, in addition to the expected whl files.

Expected behavior

Only wheels should be generated to the wheel-dir directory.

Analysis

This issue probably originates in #8843 around here although I'm not entirely sure yet.

[sbidoul]

Tentatively adding to 20.3 milestone as it looks like a regression.

[uranusjr]

Probably off-topic, but it feels weird to me that wheel accepts an editable requirement; I would expect it to error, or convert the requirement to non-editable with a warning.

[sbidoul]

@uranusjr see #3291 for why it exists (in a nutshell, creating installation bundles from requirement files).

[sbidoul]

I propose a fix in #9123. @McSinyx @pradyunsg since you worked on #8843 (and @pradyunsg actually had suspicions about that particular change), you input will be valuable here.