Fix a bug where pip-compile would ignore some of versions if prefer binary distributions

[atugushev]

Fixes #1118.

Relevant lines of code:

pip-tools/piptools/repositories/pypi.py

Lines 125 to 127 in 9865035

	candidates_by_version = lookup_table(
	all_candidates, key=lambda c: c.version, unique=True
	)

The parameter unique=True was the root of the issue and the cause of losing installation candidates. See examples of lookup_table() results below.

Before

candidates_by_version = {
    ...
    <Version('0.2.2')>: <InstallationCandidate('entrypoints', <Version('0.2.2')>, <Link https://files.pythonhosted.org/packages/f8/ad/0e77a853c745a15981ab51fa9a0cb4eca7a7a007b4c1970106ee6ba01e0c/entrypoints-0.2.2-py2.py3-none-any.whl#sha256=0a0685962ee5ac303f470acbb659f0f97aef5b9deb6b85d059691c706ef6e45e (from https://pypi.org/simple/entrypoints/) (requires-python:>=2.7)>)>,
    <Version('0.2.3')>: <InstallationCandidate('entrypoints', <Version('0.2.3')>, <Link https://files.pythonhosted.org/packages/27/e8/607697e6ab8a961fc0b141a97ea4ce72cd9c9e264adeb0669f6d194aa626/entrypoints-0.2.3.tar.gz#sha256=d2d587dde06f99545fb13a383d2cd336a8ff1f359c5839ce3a64c917d10c029f (from https://pypi.org/simple/entrypoints/) (requires-python:>=2.7)>)>,
    <Version('0.3')>: <InstallationCandidate('entrypoints', <Version('0.3')>, <Link https://files.pythonhosted.org/packages/b4/ef/063484f1f9ba3081e920ec9972c96664e2edb9fdc3d8669b0e3b8fc0ad7c/entrypoints-0.3.tar.gz#sha256=c70dd71abe5a8c85e55e12c19bd91ccfeec11a6e99044204511f9ed547d48451 (from https://pypi.org/simple/entrypoints/) (requires-python:>=2.7)>)>
}

Note entrypoints-0.3.tar.gz in <Version('0.3')> .

After

candidates_by_version = {
    <Version('0.2.2')>: {
        <InstallationCandidate('entrypoints', <Version('0.2.2')>, <Link https://files.pythonhosted.org/packages/f8/ad/0e77a853c745a15981ab51fa9a0cb4eca7a7a007b4c1970106ee6ba01e0c/entrypoints-0.2.2-py2.py3-none-any.whl#sha256=0a0685962ee5ac303f470acbb659f0f97aef5b9deb6b85d059691c706ef6e45e (from https://pypi.org/simple/entrypoints/) (requires-python:>=2.7)>)>
    },

    <Version('0.2.3')>: {
        <InstallationCandidate('entrypoints', <Version('0.2.3')>, <Link https://files.pythonhosted.org/packages/cc/8b/4eefa9b47f1910b3d2081da67726b066e379b04ca897acfe9f92bac56147/entrypoints-0.2.3-py2.py3-none-any.whl#sha256=10ad569bb245e7e2ba425285b9fa3e8178a0dc92fc53b1e1c553805e15a8825b (from https://pypi.org/simple/entrypoints/) (requires-python:>=2.7)>)>,
        <InstallationCandidate('entrypoints', <Version('0.2.3')>, <Link https://files.pythonhosted.org/packages/27/e8/607697e6ab8a961fc0b141a97ea4ce72cd9c9e264adeb0669f6d194aa626/entrypoints-0.2.3.tar.gz#sha256=d2d587dde06f99545fb13a383d2cd336a8ff1f359c5839ce3a64c917d10c029f (from https://pypi.org/simple/entrypoints/) (requires-python:>=2.7)>)>
    },

    <Version('0.3')>: {
        <InstallationCandidate('entrypoints', <Version('0.3')>, <Link https://files.pythonhosted.org/packages/b4/ef/063484f1f9ba3081e920ec9972c96664e2edb9fdc3d8669b0e3b8fc0ad7c/entrypoints-0.3.tar.gz#sha256=c70dd71abe5a8c85e55e12c19bd91ccfeec11a6e99044204511f9ed547d48451 (from https://pypi.org/simple/entrypoints/) (requires-python:>=2.7)>)>,
        <InstallationCandidate('entrypoints', <Version('0.3')>, <Link https://files.pythonhosted.org/packages/ac/c6/44694103f8c221443ee6b0041f69e2740d89a25641e62fb4f2ee568f2f9c/entrypoints-0.3-py2.py3-none-any.whl#sha256=589f874b313739ad35be6e0cd7efde2a4e9b6fea91edcc34e58ecbb8dbe56d19 (from https://pypi.org/simple/entrypoints/) (requires-python:>=2.7)>)>
    }
}

Changelog-friendly one-liner: Fix a bug where pip-compile would ignore some of package versions when PIP_PREFER_BINARY is on.

Contributor checklist

• Provided the tests for the changes.
• Gave a clear one-line description in the PR (that the maintainers can add to CHANGELOG.md on release).
• Assign the PR to an existing or new milestone for the target version (following Semantic Versioning).

[atugushev]

NOTE: This comment is no longer relevant after the latest 5.0.0 refactoring.

[codecov]

Codecov Report

Merging #1119 into master will increase coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #1119      +/-   ##
==========================================
+ Coverage   99.47%   99.48%   +0.01%     
==========================================
  Files          37       36       -1     
  Lines        2680     2736      +56     
  Branches      322      324       +2     
==========================================
+ Hits         2666     2722      +56     
  Misses          8        8              
  Partials        6        6              

Impacted Files	Coverage Δ
piptools/repositories/pypi.py	95.41% <100.00%> (ø)
tests/conftest.py	100.00% <100.00%> (ø)
tests/test_cli_compile.py	100.00% <100.00%> (ø)
tests/test_data/packages/fake_with_deps/setup.py

---

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[AndydeCleyre]

Very nice!

Can you just change all the new docstring instances of "by" to "from"? And maybe the "is exist" to "existing"?

[atugushev]

Thanks, @AndydeCleyre!