Document the process of generating code coverage
Update the script to check coverage generation is enabled, and provide a sensible error message if it is not.
Change-Id: I42f2b97d18bb3be2d081200cb682ea310476943f
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/70520
Kokoro: Kokoro <noreply+kokoro@google.com>
Commit-Queue: Ben Clayton <bclayton@chromium.org>
Reviewed-by: David Neto <dneto@google.com>
diff --git a/docs/coverage-info.md b/docs/coverage-info.md
new file mode 100644
index 0000000..fdb79df
--- /dev/null
+++ b/docs/coverage-info.md
@@ -0,0 +1,24 @@
+# Generating and viewing Tint code-coverage
+
+Requirements:
+
+* Host running Linux or macOS
+* Clang toolchain on the `PATH` environment variable
+
+## Building Tint with coverage generation enabled
+
+Follow the steps [to build Tint with CMake](../README.md), but include the additional `-DTINT_EMIT_COVERAGE=1` CMake flag.
+
+## Generate coverage information
+
+Use the `<tint>/tools/tint-generate-coverage` script to run the tint executable or unit tests and generate the coverage information.
+
+The script takes the executable to invoke as the first command line argument, followed by additional arguments to pass to the executable.
+
+For example, to see the code coverage for all unit tests, run:
+`<tint>/tools/tint-generate-coverage <build>/tint_unittests --gtest_brief`
+
+The script will emit two files at the root of the tint directory:
+
+* `coverage.summary` - A text file giving a coverage summary for all Tint source files.
+* `lcov.info` - A binary coverage file that can be consumed with the [VSCode Coverage Gutters](https://marketplace.visualstudio.com/items?itemName=ryanluker.vscode-coverage-gutters) extension.
diff --git a/tools/tint-generate-coverage b/tools/tint-generate-coverage
index b7ff48b..5136a1e 100755
--- a/tools/tint-generate-coverage
+++ b/tools/tint-generate-coverage
@@ -44,9 +44,22 @@
LCOV_FILE="${ROOT_DIR}/lcov.info"
SUMMARY_FILE="${ROOT_DIR}/coverage.summary"
+# Remove any existing coverage data and intermediate files
+if [ -f "$PROFRAW_FILE" ]; then rm ${PROFRAW_FILE}; fi
+if [ -f "$PROFDATA_FILE" ]; then rm ${PROFDATA_FILE}; fi
+if [ -f "$LCOV_FILE" ]; then rm ${LCOV_FILE}; fi
+if [ -f "$SUMMARY_FILE" ]; then rm ${SUMMARY_FILE}; fi
+
# Run the executable to generate the raw coverage data
# https://clang.llvm.org/docs/SourceBasedCodeCoverage.html#running-the-instrumented-program
-LLVM_PROFILE_FILE="${PROFRAW_FILE}" $@
+LLVM_PROFILE_FILE="${PROFRAW_FILE}" "$@"
+
+# Check that coverage information was generated
+if [ ! -f "$PROFRAW_FILE" ]; then
+ echo "lcov.info was not generated. Is coverage generation enabled?"
+ echo "To enable, run cmake with -DTINT_EMIT_COVERAGE=1".
+ exit 1
+fi
# Fail on any error after running the target executable
set -e
@@ -62,5 +75,5 @@
# Generate summary report
llvm-cov report --ignore-filename-regex="(.*_test\.cc|third_party/.*)" --instr-profile="${PROFDATA_FILE}" --object=${TARGET_EXE} > "${SUMMARY_FILE}"
-# Clean up
+# Clean up intermediate files
rm ${PROFRAW_FILE} ${PROFDATA_FILE}
