Validate version in build tools directory discovery for android sdk repository

Inspired from #146

PiperOrigin-RevId: 582341456
Change-Id: I40930d75746d9217ae2eb197f343f35d0276260b

Author: rjobredeaux3

rules/android_revision.bzl

@@ -26,6 +26,9 @@ AndroidRevisionInfo = provider(
     },
 )
 
+def is_android_revision(input):
+    return all([c.isdigit() for c in input.strip().split(".")])
+
 def parse_android_revision(input):
     """Parse and Android revision string and return an AndroidRevisionInfo.
 
@@ -35,10 +38,10 @@ def parse_android_revision(input):
     Returns:
       An AndroidRevisionInfo provider representing the input.
     """
-    input = input.strip()
-    parts = input.split(".")
-    if len(parts) < 1:
+    if not is_android_revision(input):
         fail("Invalid Android revision %s" % input)
+    parts = input.strip().split(".")
+
     major = int(parts[0]) if len(parts) >= 1 else 0
     minor = int(parts[1]) if len(parts) >= 2 else 0
     micro = int(parts[2]) if len(parts) >= 3 else 0

rules/android_sdk_repository/rule.bzl

@@ -14,7 +14,12 @@
 
 """Bazel rule for Android sdk repository."""
 
-load("//rules:android_revision.bzl", "compare_android_revisions", "parse_android_revision")
+load(
+    "//rules:android_revision.bzl",
+    "compare_android_revisions",
+    "is_android_revision",
+    "parse_android_revision",
+)
 
 _SDK_REPO_TEMPLATE = Label(":template.bzl")
 _EMPTY_SDK_REPO_TEMPLATE = Label(":empty.template.bzl")
@@ -59,8 +64,9 @@ def _newest_build_tools(repo_ctx, android_sdk_path):
         return None
     for entry in build_tools_path.readdir():
         name = entry.basename
-        revision = parse_android_revision(name)
-        highest = compare_android_revisions(highest, revision)
+        if is_android_revision(name):
+            revision = parse_android_revision(name)
+            highest = compare_android_revisions(highest, revision)
     return highest
 
 def _find_system_images(repo_ctx, android_sdk_path):

test/rules/android_sdk_repository/test_lib.sh

@@ -110,10 +110,12 @@ EOF
 }
 
 function test_build_tools_largest() {
-  # create several build tools
+  # create several build tools, including ones with malformed names
+  # (e.g. .DStore) to confirm they are properly excluded and do not cause
+  # crashes.
   local sdk_path="$(create_android_sdk)"
   add_platforms "${sdk_path}" 31
-  add_build_tools "${sdk_path}" 10.1.2 20.2.3 30.3.4
+  add_build_tools "${sdk_path}" 10.1.2 20.2.3 30.3.4 .DStore
 
   # Add to repository.
   cat >> WORKSPACE <<EOF