Made it easier to generically reference the source repo for a particu…

…lar distribution

Each distro package under the @pip repo now contains a `repos.bzl` file with variables
for conveniently accessing the label of each source repo. This can be used for more
easily accessing data files.

Resolves #29

src/bin/generate_pip_repositories.py

@@ -141,6 +141,7 @@ def _build_requirement_tree(self):
         for environment_name, environment_details in self.environments.items():
             python_version = environment_details["python_version"]
             sys_platform = environment_details["sys_platform"]
+            bazel_platform = _convert_sys_platform_to_bazel(sys_platform)
             requirements = environment_details["requirements"]
 
             for requirement_name, requirement_details in requirements.items():
@@ -150,7 +151,7 @@ def _build_requirement_tree(self):
                     normalized_name, {}
                 ).setdefault(
                     python_version, {}
-                )[sys_platform] = requirement_details
+                )[bazel_platform] = requirement_details
 
         return tree
 
@@ -172,6 +173,14 @@ def _generate_package_for_requirement(
 
         write_file(build_file_path, build_file_content)
 
+        repos_file_path = os.path.join(package_dir, "repos.bzl")
+        repos_file_content = self._generate_repos_file_content(
+            requirement_name,
+            python_subtree,
+        )
+
+        write_file(repos_file_path, repos_file_content)
+
     def _generate_build_file_content(self, build_rules):
         return textwrap.dedent("""
             package(default_visibility = ["//visibility:public"])
@@ -185,12 +194,12 @@ def _generate_rules_for_requirement(self, requirement_name, python_subtree):
         top_alias = SelectAlias(requirement_name)
 
         for python_version, platform_subtree in python_subtree.items():
-            for sys_platform, requirement_details in platform_subtree.items():
+            for platform, requirement_details in platform_subtree.items():
                 yield self._generate_py_library(
                     requirement_name,
                     requirement_details,
                     python_version,
-                    sys_platform,
+                    platform,
                 )
 
             version_alias = self._generate_python_version_alias(
@@ -211,11 +220,11 @@ def _generate_py_library(
         requirement_name,
         requirement_details,
         python_version,
-        sys_platform,
+        platform,
     ):
         name = _make_environment_specific_alias(
             python_version,
-            sys_platform,
+            platform,
         )
         deps = list(self._generate_dependency_labels(requirement_details))
 
@@ -230,7 +239,7 @@ def _generate_py_library(
         )
 
     def _generate_dependency_labels(self, requirement_details):
-        yield _make_source_label(requirement_details["source"])
+        yield _make_source_lib_label(requirement_details["source"])
         for dep in requirement_details["dependencies"]:
             dep_name = _normalize_distribution_name(dep)
             yield _make_package_label(dep_name)
@@ -245,18 +254,44 @@ def _generate_python_version_alias(
             _make_python_specific_alias(python_version)
         )
 
-        for sys_platform in platform_subtree:
-            bazel_platform = _convert_sys_platform_to_bazel(sys_platform)
+        for platform in platform_subtree:
+            bazel_platform = _convert_sys_platform_to_bazel(platform)
 
             platform_label = _make_platform_label(self.rules_pip_repo, bazel_platform)
 
             alias.actual[platform_label] = _make_environment_specific_alias(
                 python_version,
-                sys_platform,
+                platform,
             )
 
         return alias
 
+    def _generate_repos_file_content(self, requirement_name, python_subtree):
+        return "\n\n".join(self._generate_repo_variables(python_subtree))
+
+    def _generate_repo_variables(self, python_subtree):
+        all_seen = set()
+
+        for python_version, platform_subtree in python_subtree.items():
+            seen_for_python_version = set()
+
+            for platform, requirement_details in platform_subtree.items():
+                name = _make_environment_specific_alias(python_version, platform)
+                repo_label = _make_source_repo_label(requirement_details["source"])
+
+                yield _make_variable_definition(name, repo_label)
+
+                seen_for_python_version.add(repo_label)
+
+            if len(seen_for_python_version) == 1:
+                name = _make_python_specific_alias(python_version)
+                yield _make_variable_definition(name, list(seen_for_python_version)[0])
+
+            all_seen.update(seen_for_python_version)
+
+        if len(all_seen) == 1:
+            yield _make_variable_definition("all", list(all_seen)[0])
+
 
 def _normalize_distribution_name(name):
     return name.lower().replace("-", "_")
@@ -266,8 +301,8 @@ def _make_python_specific_alias(python_version):
     return "py{}".format(python_version)
 
 
-def _make_environment_specific_alias(python_version, sys_platform):
-    return "py{}_{}".format(python_version, sys_platform)
+def _make_environment_specific_alias(python_version, platform):
+    return "py{}_{}".format(python_version, platform)
 
 
 def _make_python_version_label(version):
@@ -281,14 +316,22 @@ def _make_platform_label(rules_pip_repo, platform):
     )
 
 
-def _make_source_label(source_name):
-    return "@{}//:lib".format(get_source_repo_name(source_name))
+def _make_source_lib_label(source_name):
+    return "{}//:lib".format(_make_source_repo_label(source_name))
+
+
+def _make_source_repo_label(source_name):
+    return "@{}".format(get_source_repo_name(source_name))
 
 
 def _make_package_label(name):
     return "//{}".format(name)
 
 
+def _make_variable_definition(name, value):
+    return '{} = "{}"'.format(name, value)
+
+
 def _convert_sys_platform_to_bazel(sys_platform):
     if sys_platform == "darwin":
         return "osx"

test/BUILD

@@ -1,3 +1,5 @@
+load("@pip//pyang:repos.bzl", pyang_repo = "all")
+
 py_test(
     name = "conditional_dependencies_test_py2",
     srcs = ["conditional_dependencies_test.py"],
@@ -59,7 +61,7 @@ py_test(
 
 genrule(
     name = "pyang-main",
-    srcs = ["@pip__pyang_1_7_8_py2_py3_none_any//scripts:pyang"],
+    srcs = [pyang_repo + "//scripts:pyang"],
     outs = ["pyang-main.py"],
     cmd = "cp $< $@",
 )
@@ -74,7 +76,7 @@ py_binary(
 
 genrule(
     name = "test-yin",
-    srcs = ["@pip__pyang_1_7_8_py2_py3_none_any//data/share/yang/modules/ietf:ietf-yang-metadata.yang"],
+    srcs = [pyang_repo + "//data/share/yang/modules/ietf:ietf-yang-metadata.yang"],
     outs = ["ietf-yang-metadata-generated.yin"],
     tools = [":pyang-exe"],
     cmd = "$(location :pyang-exe) -f yin -o $@ $<",