fix: declare typing-extensions and packaging as runtime dependencies

AGENTS.md

@@ -1,6 +1,6 @@
 # AGENTS.md
 
-`that-depends` is a zero-dependency, typed dependency-injection framework for Python
+`that-depends` is a typed dependency-injection framework for Python
 3.10+. It is the org's most-used package and the only repo here with real external
 contributor traffic: most merged PRs come from someone other than the maintainer.
 Assume a human reviews your diff.

README.md

@@ -29,7 +29,6 @@ It is production-ready and gives you the following:
 - Dependency context management with scopes.
 - Overriding dependencies for tests.
 - Injecting dependencies in functions and coroutines without wiring.
-- Package with zero dependencies.
 
 
 ### Installation

docs/dev/main-decisions.md

@@ -8,3 +8,6 @@
 3. Focus on maximum compatibility with mypy:
    - no need for `# type: ignore`
    - no need for `typing.cast`
+4. The only runtime dependency is `typing-extensions`:
+   - it backports `override`, `Self`, `TypeIs` and `TypeVar` defaults to Python 3.10;
+   - integrations declare their own imports in extras, and `tests/test_packaging.py` checks both.

pyproject.toml

@@ -20,13 +20,17 @@ classifiers = [
     "Topic :: Software Development :: Libraries",
 ]
 version = "0"
+dependencies = [
+    "typing-extensions>=4.14.1",
+]
 
 [project.optional-dependencies]
 fastapi = [
     "fastapi>=0.115.3",
 ]
 faststream = [
-    "faststream>=0.3.14"
+    "faststream>=0.5.19",
+    "packaging",
 ]
 
 [project.urls]
@@ -45,11 +49,11 @@ dev = [
     "pytest-repeat",
     "ruff",
     "mypy",
-    "typing-extensions",
     "pre-commit",
     "litestar",
     "faststream[nats]",
     "pytest-randomly",
+    "tomli",
     "pyrefly>=0.61.1",
 ]
 

tests/test_packaging.py

@@ -0,0 +1,52 @@
+import ast
+import pathlib
+import re
+import sys
+
+import that_depends
+
+
+if sys.version_info >= (3, 11):  # pragma: no cover
+    import tomllib
+else:  # pragma: no cover
+    import tomli as tomllib
+
+_PACKAGE_DIR = pathlib.Path(that_depends.__file__).parent
+_INTEGRATIONS_DIR = _PACKAGE_DIR / "integrations"
+_PROJECT = tomllib.loads((_PACKAGE_DIR.parent / "pyproject.toml").read_text())["project"]
+
+
+def _top_level_imports(path: pathlib.Path) -> set[str]:
+    roots: set[str] = set()
+    for node in ast.parse(path.read_text()).body:
+        if isinstance(node, ast.Import):
+            roots.update(alias.name.split(".")[0] for alias in node.names)
+        elif isinstance(node, ast.ImportFrom) and node.level == 0 and node.module:
+            roots.add(node.module.split(".")[0])
+    return roots
+
+
+def _normalize(name: str) -> str:
+    return re.sub(r"[-_.]+", "-", name).lower()
+
+
+def _third_party_imports(paths: list[pathlib.Path]) -> set[str]:
+    imported = set().union(*(_top_level_imports(path) for path in paths))
+    return {_normalize(name) for name in imported if name not in sys.stdlib_module_names and name != "that_depends"}
+
+
+def _declared(*, include_extras: bool) -> set[str]:
+    requirements = list(_PROJECT.get("dependencies", []))
+    if include_extras:
+        requirements += [req for extra in _PROJECT.get("optional-dependencies", {}).values() for req in extra]
+    return {_normalize(re.split(r"[\s;<>=!~\[]", requirement, maxsplit=1)[0]) for requirement in requirements}
+
+
+def test_core_runtime_imports_are_unconditional_dependencies() -> None:
+    core = [path for path in _PACKAGE_DIR.rglob("*.py") if _INTEGRATIONS_DIR not in path.parents]
+    assert _third_party_imports(core) <= _declared(include_extras=False)
+
+
+def test_integration_runtime_imports_are_declared_dependencies() -> None:
+    integrations = list(_INTEGRATIONS_DIR.rglob("*.py"))
+    assert _third_party_imports(integrations) <= _declared(include_extras=True)