refactor(pypi): improve missing package error messages

Improve the error messages thrown when a PyPI package is not available to include action-oriented tips. Update the integration test expected assertions accordingly.

Author: rickeylev

python/private/pypi/missing_package.bzl

@@ -6,12 +6,19 @@ load("//python/private:reexports.bzl", "BuiltinPyInfo")
 def _missing_package_error_impl(ctx):
     out = ctx.actions.declare_file(ctx.label.name + ".error")
 
+    if ctx.attr.hub_name:
+        hub_clause = ' when building under PyPI hub "{hub}". Try adding it to the requirements of this hub (e.g. requirements_lock or requirements_by_platform in pip.parse)'.format(
+            hub = ctx.attr.hub_name,
+        )
+    else:
+        hub_clause = ' because no default PyPI hub was configured. Try designating a default hub via pip.default(default_hub = "...") or select a hub using --@rules_python//python/config_settings:venv'
+
     # Register an action that fails when Bazel attempts to stage/build this file
     ctx.actions.run_shell(
         outputs = [out],
         command = "echo 'ERROR: PyPI package \"{pkg}\" is not available{hub_clause}.' >&2 && exit 1".format(
             pkg = ctx.attr.package_name,
-            hub_clause = (' when building under PyPI hub "%s"' % ctx.attr.hub_name) if ctx.attr.hub_name else " because no PyPI hub or default hub is requested",
+            hub_clause = hub_clause,
         ),
     )
 

tests/integration/unified_pypi_test.py

@@ -30,7 +30,7 @@ def test_disjoint_package_cquery_succeeds_but_build_fails(self):
         )
         self.assert_result_matches(
             result,
-            'ERROR: PyPI package "six" is not available when building under PyPI hub "pypi_a".',
+            'ERROR: PyPI package "six" is not available when building under PyPI hub "pypi_a"\\. Try adding it to the requirements of this hub',
         )
 
     def test_sibling_extra_alias_cquery_succeeds_but_build_fails(self):
@@ -43,7 +43,7 @@ def test_sibling_extra_alias_cquery_succeeds_but_build_fails(self):
         )
         self.assert_result_matches(
             result,
-            'ERROR: PyPI package "colorama:my_colorama" is not available when building under PyPI hub "pypi_b".',
+            'ERROR: PyPI package "colorama:my_colorama" is not available when building under PyPI hub "pypi_b"\\. Try adding it to the requirements of this hub',
         )
 
     @contextlib.contextmanager
@@ -83,7 +83,7 @@ def test_unimplemented_declared_dep_fails_build(self):
         self.assertNotEqual(result.exit_code, 0)
         self.assert_result_matches(
             result,
-            'ERROR: PyPI package "declared_only_pkg" is not available when building under PyPI hub "pypi_b".',
+            'ERROR: PyPI package "declared_only_pkg" is not available when building under PyPI hub "pypi_b"\\. Try adding it to the requirements of this hub',
         )
 
     def test_unimplemented_declared_dep_alias_fails_build(self):
@@ -92,7 +92,7 @@ def test_unimplemented_declared_dep_alias_fails_build(self):
         self.assertNotEqual(result.exit_code, 0)
         self.assert_result_matches(
             result,
-            'ERROR: PyPI package "declared_only_pkg:declared-only-alias" is not available when building under PyPI hub "pypi_b".',
+            'ERROR: PyPI package "declared_only_pkg:declared-only-alias" is not available when building under PyPI hub "pypi_b"\\. Try adding it to the requirements of this hub',
         )