Don't raise an error if there are spaces in file paths supplied to PIP_CONSTRAINT

pyodide_build/build_env.py

@@ -334,13 +334,16 @@ def _create_constraints_file() -> str:
     if not constraints:
         return ""
 
-    if len(constraints.split(maxsplit=1)) > 1:
-        raise ValueError(
-            "PIP_CONSTRAINT contains spaces so pip will misinterpret it. Make sure the path to pyodide has no spaces.\n"
-            "See https://github.com/pypa/pip/issues/13283"
-        )
-
+    # If a path to a file specified PIP_CONSTRAINT contains spaces, pip will misinterpret
+    # it as multiple files; see https://github.com/pypa/pip/issues/13283
+    # We work around this by converting the path to a URI.
     constraints_file = Path(constraints)
+    constraints = (
+        constraints_file.as_uri()
+        if " " in str(constraints_file)
+        else str(constraints_file)
+    )
+
     if not constraints_file.is_file():
         constraints_file.parent.mkdir(parents=True, exist_ok=True)
         constraints_file.write_text("")

pyodide_build/recipe/builder.py

@@ -136,11 +136,9 @@ def __init__(
         self.build_dir = (
             Path(build_dir).resolve() if build_dir else self.pkg_root / "build"
         )
-        if len(str(self.build_dir).split(maxsplit=1)) > 1:
-            raise ValueError(
-                "PIP_CONSTRAINT contains spaces so pip will misinterpret it. Make sure the path to the package build directory has no spaces.\n"
-                "See https://github.com/pypa/pip/issues/13283"
-            )
+        # If a path to a file specified PIP_CONSTRAINT contains spaces, pip will misinterpret
+        # it as multiple files; see https://github.com/pypa/pip/issues/13283
+        # We work around this by converting the path to a URI when needed.
         self.library_install_prefix = self.build_dir.parent.parent / ".libs"
         self.src_extract_dir = (
             self.build_dir / self.fullname
@@ -367,7 +365,7 @@ def _download_and_extract(self) -> None:
         shutil.move(self.build_dir / extract_dir_name, self.src_extract_dir)
         self.src_dist_dir.mkdir(parents=True, exist_ok=True)
 
-    def _create_constraints_file(self) -> str:
+    def _create_constraints_file(self, filename: str = "constraints.txt") -> str:
         """
         Creates a pip constraints file by concatenating global constraints (PIP_CONSTRAINT)
         with constraints specific to this package.
@@ -381,12 +379,24 @@ def _create_constraints_file(self) -> str:
             # nothing to override
             return host_constraints
 
-        new_constraints_file = self.build_dir / "constraints.txt"
+        new_constraints_file = self.build_dir / filename
         with new_constraints_file.open("w") as f:
             for constraint in constraints:
                 f.write(constraint + "\n")
 
-        return host_constraints + " " + str(new_constraints_file)
+        # If a path to a file specified PIP_CONSTRAINT contains spaces, pip will misinterpret
+        # it as multiple files; see https://github.com/pypa/pip/issues/13283
+        # We work around this by converting the path to a URI.
+        new_constraints_str = (
+            new_constraints_file.as_uri()
+            if " " in str(new_constraints_file)
+            else str(new_constraints_file)
+        )
+
+        if host_constraints:
+            return host_constraints + " " + new_constraints_str
+        else:
+            return new_constraints_str
 
     def _compile(
         self,

pyodide_build/tests/recipe/test_builder.py

@@ -203,6 +203,29 @@ def test_create_constraints_file_override(tmp_path, dummy_xbuildenv):
     assert data[-3:] == ["numpy < 2.0", "pytest == 7.0", "setuptools < 75"], data
 
 
+def test_create_constraints_file_space_in_path_uri_conversion(
+    tmp_path, dummy_xbuildenv
+):
+    build_dir_with_spaces = tmp_path / "build dir with spaces"
+    build_dir_with_spaces.mkdir()
+
+    builder = RecipeBuilder.get_builder(
+        recipe=RECIPE_DIR / "pkg_test_constraint",
+        build_args=BuildArgs(),
+        build_dir=build_dir_with_spaces,
+    )
+
+    paths = builder._create_constraints_file(filename="constraints with space.txt")
+
+    parts = paths.split()
+    if len(parts) > 1:
+        last_part = parts[-1]
+        if "with%20space" in last_part or last_part.startswith("file://"):
+            assert True
+        else:
+            assert "constraints with space.txt" in last_part
+
+
 class MockSourceSpec(_SourceSpec):
     @pydantic.model_validator(mode="after")
     def _check_patches_extra(self) -> Self:

pyodide_build/tests/test_build_env.py

@@ -237,3 +237,23 @@ def test_wheel_paths(dummy_xbuildenv):
             f"{current_version}-none-any",
         ]
     )
+
+
+def test_create_constraints_file_with_spaces(tmp_path, monkeypatch, reset_cache):
+    from pyodide_build.build_env import _create_constraints_file
+
+    constraints_dir = tmp_path / "path with spaces"
+    constraints_dir.mkdir()
+    constraints_file = constraints_dir / "constraints.txt"
+    constraints_file.write_text("numpy==1.0\n")
+
+    def mock_get_build_flag(name):
+        if name == "PIP_CONSTRAINT":
+            return str(constraints_file)
+
+    monkeypatch.setattr("pyodide_build.build_env.get_build_flag", mock_get_build_flag)
+
+    result = _create_constraints_file()
+
+    assert result.startswith("file://")
+    assert "path%20with%20spaces" in result or "path with spaces" in result