Added get_dependency_min_version_spec function (#62)

src/lightning_utilities/core/imports.py

@@ -4,10 +4,12 @@
 import importlib
 import operator
 from functools import lru_cache
+from importlib import metadata
 from importlib.util import find_spec
 from typing import Callable
 
 import pkg_resources
+from packaging.requirements import Requirement
 from packaging.version import Version
 
 
@@ -107,3 +109,21 @@ def __str__(self) -> str:
 
     def __repr__(self) -> str:
         return self.__str__()
+
+
+def get_dependency_min_version_spec(package_name: str, dependency_name: str) -> str:
+    """Returns the minimum version specifier of a dependency of a package.
+
+    >>> get_dependency_min_version_spec("pytorch-lightning", "jsonargparse")
+    '>=4.12.0'
+    """
+    dependencies = metadata.requires(package_name) or []
+    for dep in dependencies:
+        dependency = Requirement(dep)
+        if dependency.name == dependency_name:
+            spec = [str(s) for s in dependency.specifier if str(s)[0] == ">"]
+            return spec[0] if spec else ""
+    raise ValueError(
+        "This is an internal error. Please file a GitHub issue with the error message. Dependency "
+        f"{dependency_name!r} not found in package {package_name!r}."
+    )

tests/unittests/core/test_imports.py

@@ -1,6 +1,15 @@
 import operator
+import re
+from importlib.metadata import PackageNotFoundError
 
-from lightning_utilities.core.imports import compare_version, module_available, RequirementCache
+import pytest
+
+from lightning_utilities.core.imports import (
+    compare_version,
+    get_dependency_min_version_spec,
+    module_available,
+    RequirementCache,
+)
 
 
 def test_module_exists():
@@ -38,3 +47,14 @@ def test_requirement_cache():
     assert RequirementCache(f"pytest>={pytest.__version__}")
     assert not RequirementCache(f"pytest<{pytest.__version__}")
     assert "pip install -U '-'" in str(RequirementCache("-"))
+
+
+def test_get_dependency_min_version_spec():
+    attrs_min_version_spec = get_dependency_min_version_spec("pytest", "attrs")
+    assert re.match(r"^>=[\d.]+$", attrs_min_version_spec)
+
+    with pytest.raises(ValueError, match="'invalid' not found in package 'pytest'"):
+        get_dependency_min_version_spec("pytest", "invalid")
+
+    with pytest.raises(PackageNotFoundError, match="invalid"):
+        get_dependency_min_version_spec("invalid", "invalid")