Add CLI option to render package README.

readme_renderer/__main__.py

@@ -1,19 +1,65 @@
 import argparse
-from readme_renderer.rst import render
+import email
+from readme_renderer.markdown import render as render_md
+from readme_renderer.rst import render as render_rst
+from readme_renderer.txt import render as render_txt
+import pathlib
+from pkg_resources import get_distribution
 import sys
 
 
-if __name__ == '__main__':
+def __main__(args=None):  # noqa: N807
     parser = argparse.ArgumentParser(
-        description="Renders a .rst README to HTML",
+        description="Renders a .md, .rst, or .txt README to HTML",
     )
-    parser.add_argument('input', help="Input README file",
-                        type=argparse.FileType('r'))
+    parser.add_argument("-p", "--package", help="Get README from package metadata",
+                        action="store_true")
+    parser.add_argument("-f", "--format", choices=["md", "rst", "txt"],
+                        help="README format (inferred from input file name or package)")
+    parser.add_argument('input', help="Input README file or package name")
     parser.add_argument('-o', '--output', help="Output file (default: stdout)",
                         type=argparse.FileType('w'), default='-')
-    args = parser.parse_args()
+    args = parser.parse_args(args)
+
+    content_format = args.format
+    if args.package:
+        distribution = get_distribution(args.input)
+        pkg_info = distribution.get_metadata(distribution.PKG_INFO)
+        message = email.message_from_string(pkg_info)
+        source = message.get_payload()
+
+        # Infer the format of the description from package metadata.
+        if not content_format:
+            content_type = message.get("Description-Content-Type", "text/x-rst")
+            if content_type == "text/x-rst":
+                content_format = "rst"
+            elif content_type == "text/markdown":
+                content_format = "md"
+            elif content_type == "text/plain":
+                content_format = "txt"
+            else:
+                raise ValueError(f"invalid content type {content_type} for package "
+                                 "`long_description`")
+    else:
+        filename = pathlib.Path(args.input)
+        content_format = content_format or filename.suffix.lstrip(".")
+        with filename.open() as fp:
+            source = fp.read()
 
-    rendered = render(args.input.read(), stream=sys.stderr)
+    if content_format == "md":
+        render = render_md
+    elif content_format == "rst":
+        render = render_rst
+    elif content_format == "txt":
+        render = render_txt
+    else:
+        raise ValueError(f"invalid README format: {content_format} (expected `md`, "
+                         "`rst`, or `txt`)")
+    rendered = render(source, stream=sys.stderr)
     if rendered is None:
         sys.exit(1)
     print(rendered, file=args.output)
+
+
+if __name__ == '__main__':
+    __main__()

tests/test_cli.py

@@ -0,0 +1,61 @@
+import pathlib
+import pytest
+from readme_renderer.__main__ import __main__
+import tempfile
+from unittest import mock
+
+
+@pytest.fixture(params=["test_CommonMark_001.md", "test_rst_003.rst",
+                        "test_GFM_001.md", "test_txt_001.txt"])
+def input_file(request):
+    return pathlib.Path("tests/fixtures", request.param)
+
+
+@pytest.mark.parametrize("output_file", [False, True])
+def test_cli_input_file(input_file, output_file):
+    if output_file:
+        with tempfile.TemporaryDirectory() as tmpdir:
+            output = pathlib.Path(tmpdir) / "output.html"
+            __main__(["-o", str(output), str(input_file)])
+            with output.open() as fp:
+                result = fp.read()
+    else:
+        with mock.patch("builtins.print") as print_:
+            __main__([str(input_file)])
+            print_.assert_called_once()
+            (result,), _ = print_.call_args
+
+    with input_file.with_suffix(".html").open() as fp:
+        expected = fp.read()
+    assert result.strip() == expected.strip()
+
+
+def test_cli_invalid_format():
+    with mock.patch("pathlib.Path.open"), \
+            pytest.raises(ValueError, match="invalid README format: invalid"):
+        __main__(["no-file.invalid"])
+
+
+def test_cli_explicit_format(input_file):
+    fmt = input_file.suffix.lstrip(".")
+    with input_file.open() as fp, \
+            mock.patch("pathlib.Path.open", return_value=fp), \
+            mock.patch("builtins.print") as print_:
+        __main__(["-f", fmt, "no-file.invalid"])
+        print_.assert_called_once()
+        (result,), _ = print_.call_args
+
+    with input_file.with_suffix(".html").open() as fp:
+        assert result.strip() == fp.read().strip()
+
+
+@pytest.mark.parametrize("package, contains", [
+    ("readme_renderer", "Readme Renderer is a library that will safely render"),
+    ("docutils", "Docutils is a modular system for processing documentation"),
+])
+def test_cli_package(package, contains):
+    with mock.patch("builtins.print") as print_:
+        __main__(["-p", package])
+        print_.assert_called_once()
+        (result,), _ = print_.call_args
+    assert contains in result