peek: add serialization of PythonArtifact object (pantsbuild#17537)

peek: add serialization of PythonArtifact object

Use a Protocol to declare how to implement object serialization, and make types compatible with Python 3.7

src/python/pants/backend/project_info/peek.py

@@ -6,7 +6,9 @@
 import collections
 import json
 from dataclasses import asdict, dataclass, is_dataclass
-from typing import Any, Iterable
+from typing import Any, Iterable, Mapping
+
+from typing_extensions import Protocol, runtime_checkable
 
 from pants.engine.collection import Collection
 from pants.engine.console import Console
@@ -26,6 +28,14 @@
 from pants.option.option_types import BoolOption
 
 
+@runtime_checkable
+class Dictable(Protocol):
+    """Make possible to avoid adding concrete types to serialize objects."""
+
+    def asdict(self) -> Mapping[str, Any]:
+        ...
+
+
 class PeekSubsystem(Outputting, GoalSubsystem):
     """Display detailed target information in JSON form."""
 
@@ -106,6 +116,8 @@ def default(self, o):
             return list(o)
         if isinstance(o, Field):
             return self.default(o.value)
+        if isinstance(o, Dictable):
+            return o.asdict()
         try:
             return super().default(o)
         except TypeError:

src/python/pants/backend/python/macros/python_artifact.py

@@ -60,7 +60,7 @@ class PythonArtifact:
     def __init__(self, **kwargs):
         """
         :param kwargs: Passed to `setuptools.setup
-          <https://pythonhosted.org/setuptools/setuptools.html>`_.
+          <https://setuptools.pypa.io/en/latest/setuptools.html>`_.
         """
         if "entry_points" in kwargs:
             # coerce entry points from Dict[str, List[str]] to Dict[str, Dict[str, str]]
@@ -79,6 +79,9 @@ def __init__(self, **kwargs):
     def kwargs(self) -> Dict[str, Any]:
         return self._kw
 
+    def asdict(self) -> Dict[str, Any]:
+        return self.kwargs
+
     def __eq__(self, other: Any) -> bool:
         if not isinstance(other, PythonArtifact):
             return False