Add tags pypi_name and pypi_version to generated py_library targets (#530)

This allows tooling to use a bazel query to reverse-engineer a requirements.txt from a transitive closure of a py_binary

examples/pip_install/BUILD

diff --git a/examples/pip_install/BUILD b/examples/pip_install/BUILD
index c57ffbd..ceb3dd3 100644
--- a/examples/pip_install/BUILD
+++ b/examples/pip_install/BUILD
@@ -1,3 +1,5 @@
+load("@bazel_skylib//rules:diff_test.bzl", "diff_test")
+load("@bazel_skylib//rules:write_file.bzl", "write_file")
 load(
     "@pip//:requirements.bzl",
     "entry_point",
@@ -64,3 +66,31 @@
     name = "requirements",
     extra_args = ["--allow-unsafe"],
 )
+
+# Assert that tags are present on resulting py_library,
+# which is useful for tooling that needs to reflect on the dep graph
+# to determine the packages it was built from.
+genquery(
+    name = "yamllint_lib_by_version",
+    expression = """
+    attr("tags", "\\bpypi_version=1.26.3\\b", "@pip//pypi__yamllint")
+    intersect
+    attr("tags", "\\bpypi_name=yamllint\\b", "@pip//pypi__yamllint")
+    """,
+    scope = [requirement("yamllint")],
+)
+
+write_file(
+    name = "write_expected",
+    out = "expected",
+    content = [
+        "@pip//pypi__yamllint:pypi__yamllint",
+        "",
+    ],
+)
+
+diff_test(
+    name = "test_query_result",
+    file1 = "expected",
+    file2 = "yamllint_lib_by_version",
+)

examples/pip_install/WORKSPACE

diff --git a/examples/pip_install/WORKSPACE b/examples/pip_install/WORKSPACE
index 245b5f9..ce5333b 100644
--- a/examples/pip_install/WORKSPACE
+++ b/examples/pip_install/WORKSPACE
@@ -3,6 +3,15 @@
 load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
 
 http_archive(
+    name = "bazel_skylib",
+    sha256 = "1c531376ac7e5a180e0237938a2536de0c54d93f5c278634818e0efc952dd56c",
+    urls = [
+        "https://github.com/bazelbuild/bazel-skylib/releases/download/1.0.3/bazel-skylib-1.0.3.tar.gz",
+        "https://mirror.bazel.build/github.com/bazelbuild/bazel-skylib/releases/download/1.0.3/bazel-skylib-1.0.3.tar.gz",
+    ],
+)
+
+http_archive(
     name = "rules_python",
     sha256 = "954aa89b491be4a083304a2cb838019c8b8c3720a7abb9c4cb81ac7a24230cea",
     url = "https://github.com/bazelbuild/rules_python/releases/download/0.4.0/rules_python-0.4.0.tar.gz",

python/pip_install/extract_wheels/lib/bazel.py

diff --git a/python/pip_install/extract_wheels/lib/bazel.py b/python/pip_install/extract_wheels/lib/bazel.py
index 7a91191..a0a1ccd 100644
--- a/python/pip_install/extract_wheels/lib/bazel.py
+++ b/python/pip_install/extract_wheels/lib/bazel.py
@@ -79,6 +79,7 @@
     dependencies: List[str],
     whl_file_deps: List[str],
     pip_data_exclude: List[str],
+    tags: List[str],
     additional_targets: List[str] = [],
 ) -> str:
     """Generate a BUILD file for an unzipped Wheel
@@ -87,6 +88,8 @@
         name: the target name of the py_library
         dependencies: a list of Bazel labels pointing to dependencies of the library
         whl_file_deps: a list of Bazel labels pointing to wheel file dependencies of this wheel.
+        pip_data_exclude: more patterns to exclude from the data attribute of generated py_library rules.
+        tags: list of tags to apply to generated py_library rules.
         additional_targets: A list of additional targets to append to the BUILD file contents.
 
     Returns:
@@ -143,6 +146,7 @@
             # search path for anything that depends on this.
             imports = ["."],
             deps = [{dependencies}],
+            tags = [{tags}],
         )
         """.format(
             name=name,
@@ -150,6 +154,7 @@
             data_exclude=json.dumps(data_exclude),
             whl_file_label=WHEEL_FILE_LABEL,
             whl_file_deps=",".join(whl_file_deps),
+            tags = ",".join(["\"%s\"" % t for t in tags]),
             data_label=DATA_LABEL,
             dist_info_label=DIST_INFO_LABEL,
             entry_point_prefix=WHEEL_ENTRY_POINT_PREFIX,
@@ -367,6 +372,7 @@
             sanitised_dependencies,
             sanitised_wheel_file_dependencies,
             pip_data_exclude,
+            ["pypi_name=" + whl.name, "pypi_version=" + whl.metadata.version],
             entry_points,
         )
         build_file.write(contents)