fix: preserve empty inline readme and license text

pyproject_metadata/project_table.py

@@ -241,6 +241,9 @@ def _(prefix: str, data: object, error_collector: SimpleErrorCollector) -> None:
     if "content-type" not in data:
         msg = f'Field "{prefix}" is missing required key "content-type"'
         error_collector.error(ConfigurationError(msg, key=prefix))
+    elif data["content-type"] == "":
+        msg = f'Field "{prefix}.content-type" must not be empty'
+        error_collector.error(ConfigurationError(msg, key=f"{prefix}.content-type"))
 
 
 @validate_via_prefix.register(r"project\.version")

pyproject_metadata/pyproject.py

@@ -127,10 +127,11 @@ def get_license(
     filename = _license.get("file")
     text = _license.get("text")
 
-    if (filename and text) or (not filename and not text):
+    # Reported by the project.license validator
+    if (filename is None) == (text is None):
         return None
 
-    if filename:
+    if filename is not None:
         file = project_dir.joinpath(filename)
         if not file.is_file():
             msg = "License file not found ({filename!r})"
@@ -212,14 +213,15 @@ def get_readme(  # noqa: C901
             if text is None:
                 return None
 
-        if (filename and text) or (not filename and not text):
+        # Reported by the project.readme validator
+        if (filename is None) == (text is None):
             return None
         if not content_type:
             return None
     else:
         return None
 
-    if filename:
+    if filename is not None:
         file = project_dir.joinpath(filename)
         if not file.is_file():
             msg = "Readme file not found ({filename!r})"

tests/test_standard_metadata.py

@@ -308,6 +308,16 @@ def all_errors(request: pytest.FixtureRequest, monkeypatch: pytest.MonkeyPatch)
             'Field "project.readme" is missing required key "content-type"',
             id="Missing content-type for readme (text only)",
         ),
+        pytest.param(
+            """
+                [project]
+                name = "test"
+                version = "0.1.0"
+                readme = { text = "...", content-type = "" }
+            """,
+            'Field "project.readme.content-type" must not be empty',
+            id="Empty content-type for readme",
+        ),
         pytest.param(
             """
                 [project]
@@ -1430,18 +1440,44 @@ def test_as_json(monkeypatch: pytest.MonkeyPatch) -> None:
     }
 
 
-def test_readme_text() -> None:
+@pytest.mark.parametrize("text", ["onetwothree", ""])
+def test_readme_text(text: str) -> None:
     pyproject = pyproject_metadata.StandardMetadata.from_pyproject(
         {
             "project": {
                 "name": "foo",
                 "version": "1.2.3",
-                "readme": {"text": "onetwothree", "content-type": "text/plain"},
+                "readme": {"text": text, "content-type": "text/plain"},
             }
         }
     )
     assert pyproject.readme
-    assert pyproject.readme.text == "onetwothree"
+    assert pyproject.readme.text == text
+    assert pyproject.readme.content_type == "text/plain"
+    assert pyproject.as_rfc822()["Description-Content-Type"] == "text/plain"
+    assert pyproject.as_json()["description"] == text
+
+
+def test_empty_license_text() -> None:
+    pyproject = pyproject_metadata.StandardMetadata.from_pyproject(
+        {"project": {"name": "x", "version": "1.0", "license": {"text": ""}}}
+    )
+    assert pyproject.license == pyproject_metadata.License("", file=None)
+    assert pyproject.as_rfc822()["License"] == ""
+
+
+@pytest.mark.parametrize(
+    ("field", "value"),
+    [
+        ("readme", {"file": "", "content-type": "text/plain"}),
+        ("license", {"file": ""}),
+    ],
+)
+def test_empty_metadata_filename(field: str, value: dict[str, str]) -> None:
+    with pytest.raises(pyproject_metadata.ConfigurationError, match="file not found"):
+        pyproject_metadata.StandardMetadata.from_pyproject(
+            {"project": {"name": "x", "version": "1.0", field: value}}
+        )
 
 
 def test_as_rfc822(monkeypatch: pytest.MonkeyPatch) -> None: