Configure Python build system (#8)

Co-authored-by: Zanie Blue <contact@zanie.dev>

python/ty/__main__.py

@@ -0,0 +1,86 @@
+from __future__ import annotations
+
+import os
+import sys
+import sysconfig
+
+
+def find_ty_bin() -> str:
+    """Return the ty binary path."""
+
+    ty_exe = "ty" + sysconfig.get_config_var("EXE")
+
+    scripts_path = os.path.join(sysconfig.get_path("scripts"), ty_exe)
+    if os.path.isfile(scripts_path):
+        return scripts_path
+
+    if sys.version_info >= (3, 10):
+        user_scheme = sysconfig.get_preferred_scheme("user")
+    elif os.name == "nt":
+        user_scheme = "nt_user"
+    elif sys.platform == "darwin" and sys._framework:
+        user_scheme = "osx_framework_user"
+    else:
+        user_scheme = "posix_user"
+
+    user_path = os.path.join(sysconfig.get_path("scripts", scheme=user_scheme), ty_exe)
+    if os.path.isfile(user_path):
+        return user_path
+
+    # Search in `bin` adjacent to package root (as created by `pip install --target`).
+    pkg_root = os.path.dirname(os.path.dirname(__file__))
+    target_path = os.path.join(pkg_root, "bin", ty_exe)
+    if os.path.isfile(target_path):
+        return target_path
+
+    # Search for pip-specific build environments.
+    #
+    # Expect to find ty in <prefix>/pip-build-env-<rand>/overlay/bin/ty
+    # Expect to find a "normal" folder at <prefix>/pip-build-env-<rand>/normal
+    #
+    # See: https://github.com/pypa/pip/blob/102d8187a1f5a4cd5de7a549fd8a9af34e89a54f/src/pip/_internal/build_env.py#L87
+    paths = os.environ.get("PATH", "").split(os.pathsep)
+    if len(paths) >= 2:
+
+        def get_last_three_path_parts(path: str) -> list[str]:
+            """Return a list of up to the last three parts of a path."""
+            parts = []
+
+            while len(parts) < 3:
+                head, tail = os.path.split(path)
+                if tail or head != path:
+                    parts.append(tail)
+                    path = head
+                else:
+                    parts.append(path)
+                    break
+
+            return parts
+
+        maybe_overlay = get_last_three_path_parts(paths[0])
+        maybe_normal = get_last_three_path_parts(paths[1])
+        if (
+            len(maybe_normal) >= 3
+            and maybe_normal[-1].startswith("pip-build-env-")
+            and maybe_normal[-2] == "normal"
+            and len(maybe_overlay) >= 3
+            and maybe_overlay[-1].startswith("pip-build-env-")
+            and maybe_overlay[-2] == "overlay"
+        ):
+            # The overlay must contain the ty binary.
+            candidate = os.path.join(paths[0], ty_exe)
+            if os.path.isfile(candidate):
+                return candidate
+
+    raise FileNotFoundError(scripts_path)
+
+
+if __name__ == "__main__":
+    ty = os.fsdecode(find_ty_bin())
+    if sys.platform == "win32":
+        import subprocess
+
+        completed_process = subprocess.run([ty, *sys.argv[1:]])
+        sys.exit(completed_process.returncode)
+    else:
+        os.execvp(ty, [ty, *sys.argv[1:]])