Selective build clobbering feature (landmines.py and android build scripts).

build/android/buildbot/buildbot_functions.sh

Index: build/android/buildbot/buildbot_functions.sh
diff --git a/build/android/buildbot/buildbot_functions.sh b/build/android/buildbot/buildbot_functions.sh
index 25e89c40a82f98eaf69a4cf47b791dd935c712bd..b1e74b143cd7bfc04c00f7c08b7c4986351e76be 100755
--- a/build/android/buildbot/buildbot_functions.sh
+++ b/build/android/buildbot/buildbot_functions.sh
@@ -18,6 +18,7 @@ function bb_parse_args {
       --factory-properties=*)
         FACTORY_PROPERTIES="$(echo "$1" | sed 's/^[^=]*=//')"
         BUILDTYPE=$(bb_get_json_prop "$FACTORY_PROPERTIES" target)
+        BUILDTOOL=$(bb_get_json_prop "$FACTORY_PROPERTIES" buildtool)
         ;;
       --build-properties=*)
         BUILD_PROPERTIES="$(echo "$1" | sed 's/^[^=]*=//')"
@@ -37,6 +38,71 @@ function bb_force_bot_green_and_exit {
   exit 0
 }
 
+# Check for landmines which might clobber the build. Will create a new annotator
+# step for the clobber if one is required.
+#
+# As a side effect, creates "$2/.landmines"
+#
+# Args:
+#   $1: source root
+#   $2: output root
+# Retval:
+#   0 if landmines are tripped for this build and we need clobber OR
+#        clobber was requested via $BUILDBOT_CLOBBER
+#   1 if landmines are dormant
+function bb_check_clobber {
+  local src_root="$1"
+  local out_dir="$2"
+
+  local ret=1
+
+  if [[ $BUILDBOT_CLOBBER ]]
+  then
+    echo "@@@BUILD_STEP Clobber@@@"
+    echo "Clobber explicitly requested"
+    ret=0
+  else
+    local landmines_path="$out_dir/.landmines"
+    local landmines_script="$src_root/build/landmines.py"
+    [[ ! -x "$landmines_script" ]] || return 1
+
+    local new_landmines=$(mktemp)
+
+    python "$landmines_script" >> "$new_landmines" <<EOF
+    {
+      "target": "$BUILDTYPE",
+      "distributor": "goma",
+      "platform": "android",
+      "builder": "$BUILDTOOL"
+    }
+EOF
+
+    if [[ ! -f "$landmines_path" ]]
+    then
+      mkdir -p "$(dirname "$landmines_path")"
+      mv "$new_landmines" "$landmines_path"
+    else
+      local diff_output=$(mktemp)
+      diff -U 0 --label "old_landmines $(stat -c "%z" "$landmines_path")" \
+                "$landmines_path"                                         \
+                --label "new_landmines $(stat -c "%z" "$new_landmines")"  \
+                "$new_landmines" > "$diff_output"
+      if [[ $? != 0 ]]
+      then
+        echo "@@@BUILD_STEP Clobber@@@"
+        echo "Landmines tripped! Clobbering the build! Reasons for clobber:"
+        cat "$diff_output"
+        ret=0
+      fi
+      rm -f "$diff_output"
+    fi
+
+    rm -f "$new_landmines"
+  fi
+
+  return $ret
+}
+
 # Basic setup for all bots to run after a source tree checkout.
 # Args:
 #   $1: source root.
@@ -47,8 +113,11 @@ function bb_baseline_setup {
   shift
   cd $SRC_ROOT
 
-  if [[ $BUILDBOT_CLOBBER ]]; then
-    echo "@@@BUILD_STEP Clobber@@@"
+  echo "@@@BUILD_STEP Parse args@@@"
+  bb_parse_args "$@"
+
+  if bb_check_clobber "$SRC_ROOT" "$SRC_ROOT/out/$BUILDTYPE"
+  then
     # Sdk key expires, delete android folder.
     # crbug.com/145860
     rm -rf ~/.android
@@ -60,9 +129,6 @@ function bb_baseline_setup {
   fi
 
   echo "@@@BUILD_STEP Environment setup@@@"
-  bb_parse_args "$@"
-
-  local BUILDTOOL=$(bb_get_json_prop "$FACTORY_PROPERTIES" buildtool)
   if [[ $BUILDTOOL = ninja ]]; then
     export GYP_GENERATORS=ninja
   fi
@@ -155,7 +221,6 @@ function bb_compile {
   # Talk to maruel for details.
   echo "@@@BUILD_STEP compile@@@"
 
-  BUILDTOOL=$(bb_get_json_prop "$FACTORY_PROPERTIES" buildtool)
   if [[ $BUILDTOOL = ninja ]]; then
     bb_goma_ninja All
   else