Move long_description metadata to pyproject.toml (#18172)

Fixes #18168

pyproject.toml

@@ -17,6 +17,17 @@ build-backend = "setuptools.build_meta"
 [project]
 name = "mypy"
 description = "Optional static typing for Python"
+readme = {text = """
+Mypy -- Optional Static Typing for Python
+=========================================
+
+Add type annotations to your Python programs, and use mypy to type
+check them.  Mypy is essentially a Python linter on steroids, and it
+can catch many programming errors by analyzing your program, without
+actually having to run it.  Mypy has a powerful type system with
+features such as type inference, gradual typing, generics and union
+types.
+""", content-type = "text/x-rst"}
 authors = [{name = "Jukka Lehtosalo", email = "[email protected]"}]
 license = {text = "MIT"}
 classifiers = [
@@ -41,7 +52,7 @@ dependencies = [
   "mypy_extensions>=1.0.0",
   "tomli>=1.1.0; python_version<'3.11'",
 ]
-dynamic = ["version", "readme"]
+dynamic = ["version"]
 
 [project.optional-dependencies]
 dmypy = ["psutil>=4.0"]

setup.py

@@ -26,18 +26,6 @@
 if TYPE_CHECKING:
     from typing_extensions import TypeGuard
 
-long_description = """
-Mypy -- Optional Static Typing for Python
-=========================================
-
-Add type annotations to your Python programs, and use mypy to type
-check them.  Mypy is essentially a Python linter on steroids, and it
-can catch many programming errors by analyzing your program, without
-actually having to run it.  Mypy has a powerful type system with
-features such as type inference, gradual typing, generics and union
-types.
-""".lstrip()
-
 
 def is_list_of_setuptools_extension(items: list[Any]) -> TypeGuard[list[Extension]]:
     return all(isinstance(item, Extension) for item in items)
@@ -171,6 +159,4 @@ def run(self):
     ext_modules = []
 
 
-setup(
-    version=version, long_description=long_description, ext_modules=ext_modules, cmdclass=cmdclass
-)
+setup(version=version, ext_modules=ext_modules, cmdclass=cmdclass)