Adopt PEP 621 Conventions

changes/1203.feature.rst

@@ -0,0 +1 @@
+Briefcase will now honor PEP-621 project fields where they map to Briefcase configuration items.

docs/reference/configuration.rst

@@ -497,3 +497,30 @@ look for ``resource/round-icon-42.png``, ``resource/square-icon-42.png``,
 -------
 
 A URL for help related to the document format.
+
+PEP621 compatibility
+====================
+
+Many of the keys that exist in Briefcase's configuration have analogous settings
+in `PEP621 project metadata
+<https://packaging.python.org/en/latest/specifications/declaring-project-metadata>`__.
+If your ``pyproject.toml`` defines a ``[project]`` section, Briefcase will honor
+those settings as a top level definition. Any ``[tool.briefcase]`` definitions
+will override those in the ``[project]`` section.
+
+The following PEP621 project metadata keys will be used by Briefcase if they are
+available:
+
+* ``version`` maps to the same key in Briefcase.
+* ``authors`` The ``email`` and ``name`` keys of the first value in the
+  ``authors`` setting map to ``author`` and ``author_email``.
+* ``dependencies`` maps to the Briefcase ``requires`` setting. This is a
+  cumulative setting; any packages defined in the ``requires`` setting at the
+  ``[tool.briefcase]`` level will be appended to the packages defined with
+  ``dependencies`` at the ``[project]`` level.
+* ``description`` maps to the same key in Briefcase.
+* ``test`` in an ``[project.optional-dependencies]`` section maps to
+  ``test_requires``., As with ``dependencies``/``requires``, this is a
+  cumulative setting.
+* ``text`` in a ``[project.license]`` section will be mapped to ``license``.
+* ``homepage`` in a ``[project.urls]`` section will be mapped to ``url``.

src/briefcase/config.py

@@ -491,6 +491,60 @@ def merge_config(config, data):
     config.update(data)
 
 
+def merge_pep621_config(global_config, pep621_config):
+    """Merge a PEP621 configuration into a Briefcase configuration."""
+
+    def maybe_update(field, *project_fields):
+        # If there's an existing key in the Briefcase config, it takes priority.
+        if field in global_config:
+            return
+
+        # Traverse the fields in the pep621 config; if the config exists, set it
+        # in the Briefcase config.
+        datum = pep621_config
+        try:
+            for key in project_fields:
+                datum = datum[key]
+        except KeyError:
+            pass
+        else:
+            global_config[field] = datum
+
+    # Keys that map direclty
+    maybe_update("description", "description")
+    maybe_update("license", "license", "text")
+    maybe_update("url", "urls", "Homepage")
+    maybe_update("version", "version")
+
+    # Use the details of the first author as the Briefcase author.
+    if "author" not in global_config:
+        try:
+            global_config["author"] = pep621_config["authors"][0]["name"]
+        except (KeyError, IndexError):
+            pass
+    if "author_email" not in global_config:
+        try:
+            global_config["author_email"] = pep621_config["authors"][0]["email"]
+        except (KeyError, IndexError):
+            pass
+
+    # Briefcase requires is cumulative over PEP621 dependencies
+    try:
+        pep621_dependencies = pep621_config["dependencies"]
+        requires = global_config.get("requires", [])
+        global_config["requires"] = pep621_dependencies + requires
+    except KeyError:
+        pass
+
+    # Briefcase test_requires is cumulative over PEP621 optional test dependencies
+    try:
+        pep621_test_dependencies = pep621_config["optional-dependencies"]["test"]
+        test_requires = global_config.get("test_requires", [])
+        global_config["test_requires"] = pep621_test_dependencies + test_requires
+    except KeyError:
+        pass
+
+
 def parse_config(config_file, platform, output_format):
     """Parse the briefcase section of the pyproject.toml configuration file.
 
@@ -521,13 +575,20 @@ def parse_config(config_file, platform, output_format):
     """
     try:
         pyproject = tomllib.load(config_file)
-
-        global_config = pyproject["tool"]["briefcase"]
     except tomllib.TOMLDecodeError as e:
         raise BriefcaseConfigError(f"Invalid pyproject.toml: {e}") from e
+
+    try:
+        global_config = pyproject["tool"]["briefcase"]
     except KeyError as e:
         raise BriefcaseConfigError("No tool.briefcase section in pyproject.toml") from e
 
+    # Merge the PEP621 configuration (if it exists)
+    try:
+        merge_pep621_config(global_config, pyproject["project"])
+    except KeyError:
+        pass
+
     # For consistent results, sort the platforms and formats
     all_platforms = sorted(get_platforms().keys())
     all_formats = sorted(get_output_formats(platform).keys())