ARROW-1728: [C++] Run clang-format checks in Travis CI

While this will result in more build failures, it will help keep master clean to avoid unrelated noise diffs in later patches (which has been frequently happening)

Author: Wes McKinney <[email protected]>

Closes #1251 from wesm/ARROW-1728 and squashes the following commits:

8a170fa [Wes McKinney] Revert flake
c57d585 [Wes McKinney] Make travis_install_clang_tools.sh executable
6b5651e [Wes McKinney] Implement check-format in run_clang_format.py, run in Travis CI

.travis.yml

@@ -56,6 +56,8 @@ matrix:
     - export ARROW_TRAVIS_USE_TOOLCHAIN=1
     - export ARROW_TRAVIS_VALGRIND=1
     - export ARROW_TRAVIS_PLASMA=1
+    - export ARROW_TRAVIS_CLANG_FORMAT=1
+    - $TRAVIS_BUILD_DIR/ci/travis_install_clang_tools.sh
     - $TRAVIS_BUILD_DIR/ci/travis_lint.sh
     - $TRAVIS_BUILD_DIR/ci/travis_before_script_cpp.sh
     script:

ci/travis_lint.sh

@@ -26,6 +26,10 @@ pushd $TRAVIS_BUILD_DIR/cpp/lint
 cmake ..
 make lint
 
+if [ "$ARROW_TRAVIS_CLANG_FORMAT" == "1" ]; then
+  make check-format
+fi
+
 popd
 
 # Fail fast on style checks

ci/travis_script_cpp.sh

@@ -27,14 +27,6 @@ git archive HEAD --prefix=apache-arrow/ --output=arrow-src.tar.gz
 
 pushd $CPP_BUILD_DIR
 
-# ARROW-209: checks depending on the LLVM toolchain are disabled temporarily
-# until we are able to install the full LLVM toolchain in Travis CI again
-
-# if [ $TRAVIS_OS_NAME == "linux" ]; then
-#   make check-format
-#   make check-clang-tidy
-# fi
-
 ctest -VV -L unittest
 
 popd

cpp/CMakeLists.txt

@@ -446,10 +446,10 @@ add_custom_target(format ${BUILD_SUPPORT_DIR}/run_clang_format.py
 # runs clang format and exits with a non-zero exit code if any files need to be reformatted
 
 # TODO(wesm): Make this work in run_clang_format.py
-# add_custom_target(check-format ${BUILD_SUPPORT_DIR}/run_clang_format.py
-#   ${CLANG_FORMAT_VERSION}
-#   ${BUILD_SUPPORT_DIR}/clang_format_exclusions.txt
-#   ${CMAKE_CURRENT_SOURCE_DIR}/src 1)
+add_custom_target(check-format ${BUILD_SUPPORT_DIR}/run_clang_format.py
+   ${CLANG_FORMAT_VERSION}
+   ${BUILD_SUPPORT_DIR}/clang_format_exclusions.txt
+   ${CMAKE_CURRENT_SOURCE_DIR}/src 1)
 
 ############################################################
 # "make clang-tidy" and "make check-clang-tidy" targets

cpp/build-support/run_clang_format.py

@@ -31,6 +31,12 @@
 EXCLUDE_GLOBS_FILENAME = sys.argv[2]
 SOURCE_DIR = sys.argv[3]
 
+if len(sys.argv) > 4:
+    CHECK_FORMAT = int(sys.argv[4]) == 1
+else:
+    CHECK_FORMAT = False
+
+
 exclude_globs = [line.strip() for line in open(EXCLUDE_GLOBS_FILENAME, "r")]
 
 files_to_format = []
@@ -49,18 +55,24 @@
         if not excluded:
             files_to_format.append(name)
 
-# TODO(wesm): Port this to work with Python, for check-format
-# NUM_CORRECTIONS=`$CLANG_FORMAT -output-replacements-xml  $@ |
-# grep offset | wc -l`
-# if [ "$NUM_CORRECTIONS" -gt "0" ]; then
-#   echo "clang-format suggested changes, please run 'make format'!!!!"
-#   exit 1
-# fi
+if CHECK_FORMAT:
+    output = subprocess.check_output([CLANG_FORMAT, '-output-replacements-xml']
+                                     + files_to_format,
+                                     stderr=subprocess.STDOUT).decode('utf8')
+
+    to_fix = []
+    for line in output.split('\n'):
+        if 'offset' in line:
+            to_fix.append(line)
 
-try:
-    cmd = [CLANG_FORMAT, '-i'] + files_to_format
-    subprocess.check_output(cmd, stderr=subprocess.STDOUT)
-except Exception as e:
-    print(e)
-    print(' '.join(cmd))
-    raise
+    if len(to_fix) > 0:
+        print("clang-format checks failed, run 'make format' to fix")
+        sys.exit(-1)
+else:
+    try:
+        cmd = [CLANG_FORMAT, '-i'] + files_to_format
+        subprocess.check_output(cmd, stderr=subprocess.STDOUT)
+    except Exception as e:
+        print(e)
+        print(' '.join(cmd))
+        raise