Add lint for [ instead of [[ in shells scripts

ports/geckolib/gecko_bindings/tools/regen.sh

@@ -8,25 +8,25 @@ set -o errexit
 set -o nounset
 set -o pipefail
 
-if [ ${#} -eq 0 ]; then
+if [[ ${#} -eq 0 ]]; then
   echo "Usage: ${0} /path/to/gecko/objdir [other-regen.py-flags]"
   exit 1
 fi
 
 # Check for rust-bindgen
-if [ ! -d rust-bindgen ]; then
+if [[ ! -d rust-bindgen ]]; then
   echo "rust-bindgen not found. Run setup_bindgen.sh first."
   exit 1
 fi
 
 # Check for /usr/include
-if [ ! -d /usr/include ]; then
+if [[ ! -d /usr/include ]]; then
   echo "/usr/include doesn't exist." \
        "Mac users may need to run xcode-select --install."
   exit 1
 fi
 
-if [ "$(uname)" == "Linux" ]; then
+if [[ "$(uname)" == "Linux" ]]; then
   LIBCLANG_PATH=/usr/lib/llvm-3.8/lib
 else
   LIBCLANG_PATH="$(brew --prefix llvm38)/lib/llvm-3.8/lib"

ports/geckolib/gecko_bindings/tools/setup_bindgen.sh

@@ -12,14 +12,14 @@ set -o pipefail
 cd "$(dirname ${0})"
 
 # Setup and build bindgen.
-if [ "$(uname)" == "Linux" ]; then
+if [[ "$(uname)" == "Linux" ]]; then
   export LIBCLANG_PATH=/usr/lib/llvm-3.8/lib
 else
   export LIBCLANG_PATH="$(brew --prefix llvm38)/lib/llvm-3.8/lib"
 fi
 
 # Make sure we have llvm38.
-if [ ! -x "$(command -v clang-3.8)" ]; then
+if [[ ! -x "$(command -v clang-3.8)" ]]; then
     echo "llmv38 must be installed." \
          "Mac users should |brew install llvm38|, Linux varies by distro."
     exit 1
@@ -29,13 +29,13 @@ export LD_LIBRARY_PATH="${LIBCLANG_PATH}"
 export DYLD_LIBRARY_PATH="${LIBCLANG_PATH}"
 
 # Check for multirust
-if [ ! -x "$(command -v multirust)" ]; then
+if [[ ! -x "$(command -v multirust)" ]]; then
     echo "multirust must be installed."
     exit 1
 fi
 
 # Don't try to clone twice.
-if [ ! -d rust-bindgen ]; then
+if [[ ! -d rust-bindgen ]]; then
   git clone https://github.com/servo/rust-bindgen.git
 fi
 

python/tidy/servo_tidy/tidy.py

@@ -347,6 +347,9 @@ def check_shell(file_name, lines):
         if "`" in stripped:
             yield (idx + 1, "script should not use backticks for command substitution")
 
+        if " [ " in stripped or stripped.startswith("[ "):
+            yield (idx + 1, "script should use `[[` instead of `[` for conditional testing")
+
         for dollar in re.finditer('\$', stripped):
             next_idx = dollar.end()
             if next_idx < len(stripped):

python/tidy/servo_tidy_tests/shell_tidy.sh

@@ -8,3 +8,7 @@ set -o nounset
 echo "hello world"
 some_var=`echo "command substitution"`
 another_var="$some_var"
+if [ -z "${some_var}" ]; then
+  echo "should have used [["
+fi
+[ -z "${another_var}" ]

python/tidy/servo_tidy_tests/test_tidy.py

@@ -54,6 +54,8 @@ class CheckTidiness(unittest.TestCase):
         self.assertEqual('script is missing options "set -o errexit", "set -o pipefail"', errors.next()[2])
         self.assertEqual('script should not use backticks for command substitution', errors.next()[2])
         self.assertEqual('variable substitutions should use the full \"${VAR}\" form', errors.next()[2])
+        self.assertEqual('script should use `[[` instead of `[` for conditional testing', errors.next()[2])
+        self.assertEqual('script should use `[[` instead of `[` for conditional testing', errors.next()[2])
         self.assertNoMoreErrors(errors)
 
     def test_rust(self):