Refactor constraints module

src/fromager/constraints.py

@@ -3,7 +3,7 @@
 import typing
 
 from packaging.requirements import Requirement
-from packaging.utils import canonicalize_name
+from packaging.utils import NormalizedName, canonicalize_name
 from packaging.version import Version
 
 from . import requirements_file
@@ -12,8 +12,33 @@
 
 
 class Constraints:
-    def __init__(self, data: dict[str, Requirement]):
-        self._data = {canonicalize_name(n): v for n, v in data.items()}
+    def __init__(self) -> None:
+        # mapping of canonical names to requirements
+        # NOTE: Requirement.name is not normalized
+        self._data: dict[NormalizedName, Requirement] = {}
+
+    def __iter__(self) -> typing.Iterable[NormalizedName]:
+        yield from self._data
+
+    def add_constraint(self, unparsed: str) -> None:
+        """Add new constraint, must not conflict with any existing constraints"""
+        req = Requirement(unparsed)
+        canon_name = canonicalize_name(req.name)
+        previous = self._data.get(canon_name)
+        if previous is not None:
+            raise KeyError(
+                f"{canon_name}: new constraint '{req}' conflicts with '{previous}'"
+            )
+        if requirements_file.evaluate_marker(req, req):
+            logger.debug(f"adding constraint {req}")
+            self._data[canon_name] = req
+
+    def load_constraints_file(self, constraints_file: str | pathlib.Path) -> None:
+        """Load constraints from a constraints file"""
+        logger.info("loading constraints from %s", constraints_file)
+        content = requirements_file.parse_requirements_file(constraints_file)
+        for line in content:
+            self.add_constraint(line)
 
     def get_constraint(self, name: str) -> Requirement | None:
         return self._data.get(canonicalize_name(name))
@@ -29,20 +54,3 @@ def is_satisfied_by(self, pkg_name: str, version: Version) -> bool:
         if constraint:
             return constraint.specifier.contains(version, prereleases=True)
         return True
-
-
-def _parse(content: typing.Iterable[str]) -> Constraints:
-    constraints = {}
-    for line in content:
-        req = Requirement(line)
-        if requirements_file.evaluate_marker(req, req):
-            constraints[req.name] = req
-    return Constraints(constraints)
-
-
-def load(constraints_file: str | pathlib.Path | None) -> Constraints:
-    if not constraints_file:
-        return Constraints({})
-    logger.info("loading constraints from %s", constraints_file)
-    parsed_req_file = requirements_file.parse_requirements_file(constraints_file)
-    return _parse(parsed_req_file)

src/fromager/context.py

@@ -42,12 +42,12 @@ def __init__(
             )
         self.settings = active_settings
         self.input_constraints_uri: str | None
+        self.constraints = constraints.Constraints()
         if constraints_file is not None:
             self.input_constraints_uri = constraints_file
-            self.constraints = constraints.load(constraints_file)
+            self.constraints.load_constraints_file(constraints_file)
         else:
             self.input_constraints_uri = None
-            self.constraints = constraints.Constraints({})
         self.sdists_repo = pathlib.Path(sdists_repo).absolute()
         self.sdists_downloads = self.sdists_repo / "downloads"
         self.sdists_builds = self.sdists_repo / "builds"

src/fromager/resolver.py

@@ -215,7 +215,7 @@ def __init__(
         self.include_sdists = include_sdists
         self.include_wheels = include_wheels
         self.sdist_server_url = sdist_server_url
-        self.constraints = constraints or Constraints({})
+        self.constraints = constraints or Constraints()
         self.req_type = req_type
 
     def identify(self, requirement_or_candidate: Requirement | Candidate) -> str:

tests/test_constraints.py

@@ -1,5 +1,4 @@
 import pathlib
-from unittest.mock import Mock, patch
 
 import pytest
 from packaging.requirements import Requirement
@@ -9,40 +8,66 @@
 
 
 def test_constraint_is_satisfied_by():
-    c = constraints.Constraints({"foo": Requirement("foo<=1.1")})
+    c = constraints.Constraints()
+    c.add_constraint("foo<=1.1")
     assert c.is_satisfied_by("foo", "1.1")
     assert c.is_satisfied_by("foo", Version("1.0"))
     assert c.is_satisfied_by("bar", Version("2.0"))
 
 
 def test_constraint_canonical_name():
-    c = constraints.Constraints({"flash_attn": Requirement("flash_attn<=1.1")})
+    c = constraints.Constraints()
+    c.add_constraint("flash_attn<=1.1")
     assert c.is_satisfied_by("flash_attn", "1.1")
     assert c.is_satisfied_by("flash-attn", "1.1")
     assert c.is_satisfied_by("Flash-ATTN", "1.1")
+    assert list(c) == ["flash-attn"]
 
 
 def test_constraint_not_is_satisfied_by():
-    c = constraints.Constraints({"foo": Requirement("foo<=1.1")})
+    c = constraints.Constraints()
+    c.add_constraint("foo<=1.1")
+    c.add_constraint("bar>=2.0")
     assert not c.is_satisfied_by("foo", "1.2")
     assert not c.is_satisfied_by("foo", Version("2.0"))
+    assert not c.is_satisfied_by("bar", Version("1.0"))
 
 
-def test_load_empty_constraints_file():
-    assert constraints.load(None)._data == {}
+def test_add_constraint_conflict():
+    c = constraints.Constraints()
+    c.add_constraint("foo<=1.1")
+    c.add_constraint("flit_core==2.0rc3")
+    with pytest.raises(KeyError):
+        c.add_constraint("foo<=1.1")
+    with pytest.raises(KeyError):
+        c.add_constraint("foo>1.1")
+    with pytest.raises(KeyError):
+        c.add_constraint("flit_core>2.0.0")
+    with pytest.raises(KeyError):
+        c.add_constraint("flit-core>2.0.0")
+
+
+def test_allow_prerelease():
+    c = constraints.Constraints()
+    c.add_constraint("foo>=1.1")
+    assert not c.allow_prerelease("foo")
+    c.add_constraint("bar>=1.1a0")
+    assert c.allow_prerelease("bar")
+    c.add_constraint("flit_core==2.0rc3")
+    assert c.allow_prerelease("flit_core")
 
 
 def test_load_non_existant_constraints_file(tmp_path: pathlib.Path):
     non_existant_file = tmp_path / "non_existant.txt"
+    c = constraints.Constraints()
     with pytest.raises(FileNotFoundError):
-        constraints.load(non_existant_file)
+        c.load_constraints_file(non_existant_file)
 
 
-@patch("fromager.requirements_file.parse_requirements_file")
-def test_load_constraints_file(parse_requirements_file: Mock, tmp_path: pathlib.Path):
+def test_load_constraints_file(tmp_path: pathlib.Path):
     constraint_file = tmp_path / "constraint.txt"
-    constraint_file.write_text("a\n")
-    parse_requirements_file.return_value = ["torch==3.1.0"]
-    assert constraints.load(constraint_file)._data == {
-        "torch": Requirement("torch==3.1.0")
-    }
+    constraint_file.write_text("egg\ntorch==3.1.0 # comment\n")
+    c = constraints.Constraints()
+    c.load_constraints_file(constraint_file)
+    assert list(c) == ["egg", "torch"]  # type: ignore
+    assert c.get_constraint("torch") == Requirement("torch==3.1.0")

tests/test_resolver.py

@@ -176,9 +176,8 @@ def test_provider_choose_sdist():
 
 
 def test_provider_choose_either_with_constraint():
-    constraint = constraints.Constraints(
-        {"hydra-core": Requirement("hydra-core==1.3.2")}
-    )
+    constraint = constraints.Constraints()
+    constraint.add_constraint("hydra-core==1.3.2")
     with requests_mock.Mocker() as r:
         r.get(
             "https://pypi.org/simple/hydra-core/",
@@ -204,7 +203,8 @@ def test_provider_choose_either_with_constraint():
 
 
 def test_provider_constraint_mismatch():
-    constraint = constraints.Constraints({"hydra-core": Requirement("hydra-core<=1.1")})
+    constraint = constraints.Constraints()
+    constraint.add_constraint("hydra-core<=1.1")
     with requests_mock.Mocker() as r:
         r.get(
             "https://pypi.org/simple/hydra-core/",
@@ -220,7 +220,8 @@ def test_provider_constraint_mismatch():
 
 
 def test_provider_constraint_match():
-    constraint = constraints.Constraints({"hydra-core": Requirement("hydra-core<=1.3")})
+    constraint = constraints.Constraints()
+    constraint.add_constraint("hydra-core<=1.3")
     with requests_mock.Mocker() as r:
         r.get(
             "https://pypi.org/simple/hydra-core/",
@@ -525,7 +526,8 @@ def test_resolve_github():
 
 
 def test_github_constraint_mismatch():
-    constraint = constraints.Constraints({"fromager": Requirement("fromager>=1.0")})
+    constraint = constraints.Constraints()
+    constraint.add_constraint("fromager>=1.0")
     with requests_mock.Mocker() as r:
         r.get(
             "https://api.github.com:443/repos/python-wheel-build/fromager",
@@ -547,7 +549,8 @@ def test_github_constraint_mismatch():
 
 
 def test_github_constraint_match():
-    constraint = constraints.Constraints({"fromager": Requirement("fromager<0.9")})
+    constraint = constraints.Constraints()
+    constraint.add_constraint("fromager<0.9")
     with requests_mock.Mocker() as r:
         r.get(
             "https://api.github.com:443/repos/python-wheel-build/fromager",