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PEP 627: Bring back the REQUESTED file #1549

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Aug 4, 2020
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PEP 627: Bring back the REQUESTED file #1549

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27 changes: 11 additions & 16 deletions pep-0627.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -20,7 +20,6 @@ for changing it.
Two files in installed ``.dist-info`` directories are made optional:
``RECORD`` (which PEP 376 lists as mandatory, but suggests it can be left out
for "system packages"), and ``INSTALLER``.
The ``REQUESTED`` file is removed from the specification.


Motivation
Expand Down Expand Up @@ -193,23 +192,17 @@ any ASCII string in ``INSTALLER``, rather than a lowercase identifier.
It also suggests using the command-line command, if available.


Removed ``REQUESTED`` File
--------------------------
The ``REQUESTED`` File
----------------------

The ``REQUESTED`` file, which was never implemented in ``pip``, is removed
from the specification.
The ``REQUESTED`` file is kept in the specification, with only tool-specific
notes removed.

The semantics of this file depend on all tools creating it when they should.
Since today's most popular tool, ``pip``, does not create it, the file is
not useful.
(It might be useful in environments managed by a single tool; in that case,
the tool is free to use ``REQUESTED`` as a private extension.)

(The author of this PEP considers ``REQUESTED`` an unnecessary attempt to emulate
system package managers. Recent tools tend to support creating easily
reproducible environments, rather than manage long-lived ones;
deleting the environment and starting a new one is a surprissingly good
solution to “dangling dependencies”.)
Note that tools that do not create this file effectively mark all installed
projects as “removable unless needed by another project”.
This was was the case with ``pip`` before version 20.2.
Before ``REQUESTED`` becomes commonplace, automatically uninstalling “orphaned”
projects should be done wit care.


Clarifications
Expand All @@ -227,6 +220,8 @@ future PEPs:

* Encoding of the ``RECORD`` file
* Limiting or namespacing files that can appear in ``.dist-info``
* Marking the difference between projects installed by a tool that does not
support the ``REQUESTED`` file and projects installed as dependencies


Copyright
Expand Down