Use a set for TargetPython.get_tags

This speeds up a representative pip-compile by about 40%

```
λ hyperfine -w 1 -M 3 -p 'rm req.txt || true' 'python -m piptools compile req.in --output-file req.txt --strip-extras --resolver=backtracking'
Benchmark 1: python -m piptools compile req.in --output-file req.txt --strip-extras --resolver=backtracking
  Time (mean ± σ):     28.552 s ±  2.552 s    [User: 20.477 s, System: 1.547 s]
  Range (min … max):   26.446 s … 31.390 s    3 runs

λ hyperfine -w 1 -M 3 -p 'rm req.txt || true' 'python -m piptools compile req.in --output-file req.txt --strip-extras --resolver=backtracking'
Benchmark 1: python -m piptools compile req.in --output-file req.txt --strip-extras --resolver=backtracking
  Time (mean ± σ):     17.570 s ±  0.450 s    [User: 11.537 s, System: 1.345 s]
  Range (min … max):   17.095 s … 17.989 s    3 runs
```

This makes the set.isdisjoint operation done over here much cheaper:
https://github.com/pypa/pip/blob/593b85f4a/src/pip/_internal/models/wheel.py#L92

The reason for this is because a Python usually has a lot of supported
tags. The Python I used above has 2000 supported tags! Whereas a wheel
usually only has one or two file tags.

The CPython code will unfortunately iterate over all 2000 tags to check
if there's a match. Only if the other collection is a set will CPython
think to swap the operands to iterate over the shorter collection:
https://github.com/python/cpython/blob/35963da40f/Objects/setobject.c#L1352

src/pip/_internal/commands/debug.py

@@ -5,10 +5,11 @@
 import sys
 from optparse import Values
 from types import ModuleType
-from typing import Any, Dict, List, Optional
+from typing import Any, Collection, Dict, List, Optional
 
 import pip._vendor
 from pip._vendor.certifi import where
+from pip._vendor.packaging.tags import Tag
 from pip._vendor.packaging.version import parse as parse_version
 
 from pip._internal.cli import cmdoptions
@@ -105,7 +106,7 @@ def show_tags(options: Values) -> None:
     tag_limit = 10
 
     target_python = make_target_python(options)
-    tags = target_python.get_tags()
+    tags: Collection[Tag] = target_python.get_tags()
 
     # Display the target options that were explicitly provided.
     formatted_target = target_python.format_given()
@@ -118,7 +119,7 @@ def show_tags(options: Values) -> None:
 
     if options.verbose < 1 and len(tags) > tag_limit:
         tags_limited = True
-        tags = tags[:tag_limit]
+        tags = list(tags)[:tag_limit]
     else:
         tags_limited = False
 

src/pip/_internal/index/package_finder.py

@@ -428,7 +428,7 @@ def create(
     def __init__(
         self,
         project_name: str,
-        supported_tags: List[Tag],
+        supported_tags: Set[Tag],
         specifier: specifiers.BaseSpecifier,
         prefer_binary: bool = False,
         allow_all_prereleases: bool = False,

src/pip/_internal/models/target_python.py

@@ -1,5 +1,5 @@
 import sys
-from typing import List, Optional, Tuple
+from typing import List, Optional, Set, Tuple
 
 from pip._vendor.packaging.tags import Tag
 
@@ -62,7 +62,7 @@ def __init__(
         self.py_version_info = py_version_info
 
         # This is used to cache the return value of get_tags().
-        self._valid_tags: Optional[List[Tag]] = None
+        self._valid_tags: Optional[Set[Tag]] = None
 
     def format_given(self) -> str:
         """
@@ -84,7 +84,7 @@ def format_given(self) -> str:
             f"{key}={value!r}" for key, value in key_values if value is not None
         )
 
-    def get_tags(self) -> List[Tag]:
+    def get_tags(self) -> Set[Tag]:
         """
         Return the supported PEP 425 tags to check wheel candidates against.
 
@@ -105,6 +105,6 @@ def get_tags(self) -> List[Tag]:
                 abis=self.abis,
                 impl=self.implementation,
             )
-            self._valid_tags = tags
+            self._valid_tags = set(tags)
 
         return self._valid_tags

src/pip/_internal/models/wheel.py

@@ -2,7 +2,7 @@
 name that have meaning.
 """
 import re
-from typing import Dict, Iterable, List
+from typing import Dict, Iterable, List, Set
 
 from pip._vendor.packaging.tags import Tag
 
@@ -64,7 +64,7 @@ def support_index_min(self, tags: List[Tag]) -> int:
             raise ValueError()
 
     def find_most_preferred_tag(
-        self, tags: List[Tag], tag_to_priority: Dict[Tag, int]
+        self, tags: Set[Tag], tag_to_priority: Dict[Tag, int]
     ) -> int:
         """Return the priority of the most preferred tag that one of the wheel's file
         tag combinations achieves in the given list of supported tags using the given

tests/unit/test_finder.py

@@ -137,7 +137,7 @@ def test_not_find_wheel_not_supported(self, data: TestData) -> None:
         req = install_req_from_line("simple.dist")
         target_python = TargetPython()
         # Make sure no tags will match.
-        target_python._valid_tags = []
+        target_python._valid_tags = set()
         finder = make_test_finder(
             find_links=[data.find_links],
             target_python=target_python,
@@ -221,11 +221,11 @@ def test_link_sorting(self) -> None:
                 Link("simple-1.0.tar.gz"),
             ),
         ]
-        valid_tags = [
+        valid_tags = {
             Tag("pyT", "none", "TEST"),
             Tag("pyT", "TEST", "any"),
             Tag("pyT", "none", "any"),
-        ]
+        }
         specifier = SpecifierSet()
         evaluator = CandidateEvaluator(
             "my-project",
@@ -289,11 +289,11 @@ def test_build_tag_is_less_important_than_other_tags(self) -> None:
                 Link("simple-1.0.tar.gz"),
             ),
         ]
-        valid_tags = [
+        valid_tags = {
             Tag("py3", "abi3", "linux_x86_64"),
             Tag("py3", "abi3", "linux_i386"),
             Tag("py3", "any", "none"),
-        ]
+        }
         evaluator = CandidateEvaluator(
             "my-project",
             supported_tags=valid_tags,

tests/unit/test_index.py

@@ -220,7 +220,7 @@ def test_evaluate_link__incompatible_wheel(self) -> None:
         """
         target_python = TargetPython(py_version_info=(3, 6, 4))
         # Set the valid tags to an empty list to make sure nothing matches.
-        target_python._valid_tags = []
+        target_python._valid_tags = set()
         evaluator = LinkEvaluator(
             project_name="sample",
             canonical_name="sample",
@@ -373,7 +373,7 @@ class TestCandidateEvaluator:
     )
     def test_create(self, allow_all_prereleases: bool, prefer_binary: bool) -> None:
         target_python = TargetPython()
-        target_python._valid_tags = [Tag("py36", "none", "any")]
+        target_python._valid_tags = {Tag("py36", "none", "any")}
         specifier = SpecifierSet()
         evaluator = CandidateEvaluator.create(
             project_name="my-project",
@@ -786,7 +786,7 @@ def test_make_candidate_evaluator(
         prefer_binary: bool,
     ) -> None:
         target_python = TargetPython()
-        target_python._valid_tags = [Tag("py36", "none", "any")]
+        target_python._valid_tags = {Tag("py36", "none", "any")}
         candidate_prefs = CandidatePreferences(
             prefer_binary=prefer_binary,
             allow_all_prereleases=allow_all_prereleases,

tests/unit/test_target_python.py

@@ -116,9 +116,9 @@ def test_get_tags__uses_cached_value(self) -> None:
         Test that get_tags() uses the cached value.
         """
         target_python = TargetPython(py_version_info=None)
-        target_python._valid_tags = [
+        target_python._valid_tags = {
             Tag("py2", "none", "any"),
             Tag("py3", "none", "any"),
-        ]
+        }
         actual = target_python.get_tags()
         assert actual == [Tag("py2", "none", "any"), Tag("py3", "none", "any")]