Remove var type annotations in extract_metadata_from_bazel_xml (#29463)

* Remove var type annotations in extract_metadata_from_bazel_xml

* Use plain-old Python class to store data

* No more f-string

* Remove version check in generate_projects.py

tools/buildgen/extract_metadata_from_bazel_xml.py

@@ -30,16 +30,13 @@
 # format entirely or simplify it to a point where it becomes self-explanatory
 # and doesn't need any detailed documentation.
 
-from dataclasses import asdict
-from dataclasses import dataclass
-from dataclasses import field
+import collections
 import os
 import subprocess
 from typing import Any, Dict, Iterable, List, Optional
 import xml.etree.ElementTree as ET
 
 import build_cleaner
-import yaml
 
 BuildMetadata = Dict[str, Any]
 BuildDict = Dict[str, BuildMetadata]
@@ -50,19 +47,36 @@ BuildDict = Dict[str, BuildMetadata]
 BuildYaml = Dict[str, Any]
 
 
-# This is basically a Python dict with predefined fields and types
-@dataclass()
 class ExternalProtoLibrary:
-    # The relative path of this proto library should be. Preferably, it should
-    # match the submodule path.
-    destination: str
-    # The prefix to remove in order to insure the proto import is correct. For
-    # more info, see description of https://github.com/grpc/grpc/pull/25272.
-    proto_prefix: str
-    # Following 3 fields should be filled by build metadata from Bazel.
-    urls: List[str] = field(default_factory=list)
-    hash: str = ''
-    strip_prefix: str = ''
+    """ExternalProtoLibrary is the struct about an external proto library.
+
+    Fields:
+    - destination(int): The relative path of this proto library should be.
+        Preferably, it should match the submodule path.
+    - proto_prefix(str): The prefix to remove in order to insure the proto import
+        is correct. For more info, see description of
+        https://github.com/grpc/grpc/pull/25272.
+    - urls(List[str]): Following 3 fields should be filled by build metadata from
+        Bazel.
+    - hash(str): The hash of the downloaded archive
+    - strip_prefix(str): The path to be stripped from the extracted directory, see
+        http_archive in Bazel.
+    """
+
+    def __init__(self,
+                 destination,
+                 proto_prefix,
+                 urls=None,
+                 hash="",
+                 strip_prefix=""):
+        self.destination = destination
+        self.proto_prefix = proto_prefix
+        if urls is None:
+            self.urls = []
+        else:
+            self.urls = urls
+        self.hash = hash
+        self.strip_prefix = strip_prefix
 
 
 EXTERNAL_PROTO_LIBRARIES = {
@@ -208,7 +222,7 @@ def _extract_sources(bazel_rule: BuildMetadata) -> List[str]:
                 if external_proto_library_name is not None:
                     result.append(
                         src.replace(
-                            f'@{external_proto_library_name}//',
+                            '@%s//' % external_proto_library_name,
                             EXTERNAL_PROTO_LIBRARIES[
                                 external_proto_library_name].proto_prefix).
                         replace(':', '/'))
@@ -790,7 +804,7 @@ def _generate_build_extra_metadata_for_tests(
     return test_metadata
 
 
-def _parse_http_archives(xml_tree: ET.Element) -> List[ExternalProtoLibrary]:
+def _parse_http_archives(xml_tree: ET.Element) -> 'List[ExternalProtoLibrary]':
     """Parse Bazel http_archive rule into ExternalProtoLibrary objects."""
     result = []
     for xml_http_archive in xml_tree:
@@ -829,7 +843,7 @@ def _generate_external_proto_libraries() -> List[Dict[str, Any]]:
     xml_tree = _bazel_query_xml_tree('kind(http_archive, //external:*)')
     libraries = _parse_http_archives(xml_tree)
     libraries.sort(key=lambda x: x.destination)
-    return list(map(asdict, libraries))
+    return list(map(lambda x: x.__dict__, libraries))
 
 
 def _detect_and_print_issues(build_yaml_like: BuildYaml) -> None:

tools/buildgen/generate_projects.py

@@ -25,10 +25,6 @@ from typing import Dict, List, Union
 import _utils
 import yaml
 
-if sys.version_info < (3, 6):
-    raise RuntimeError('Expected Python version > 3.6, but got %s at %s' %
-                       (sys.version_info, sys.executable))
-
 PROJECT_ROOT = os.path.join(os.path.dirname(os.path.abspath(__file__)), "..",
                             "..")
 os.chdir(PROJECT_ROOT)