Add fail-build-on-error property

Certain test runners (e.g. the SalesForce DX [Apex test runner](https://developer.salesforce.com/docs/atlas.en-us.sfdx_cli_reference.meta/sfdx_cli_reference/cli_reference_force_apex.htm)) will not necessarily return a non-zero value when they encounter failing tests. This means that a build can pass with failing tests. If we are already using this plugin to annotate failing tests when we see them, we might as well hook into it to allow ourselves to fail the build then as well.

Author: benmacleod

README.md

@@ -44,6 +44,13 @@ There are two options for this:
 * `file`
   * displays: `MyClass::UnderTest text of the failed expectation in path/to/my_class/under_test.file_ext`
 
+### `fail-build-on-error` (optional)  
+Default: `false`
+
+If this setting is true and any errors are found in the JUnit XML files during
+parsing, the annotation step will exit with a non-zero value, which should cause 
+the build to fail.
+
 ## Developing
 
 To test the junit parser (in Ruby) and plugin hooks (in Bash):

hooks/command

@@ -40,4 +40,10 @@ if grep -q "<details>" "$annotation_path"; then
   echo "--- :buildkite: Creating annotation"
   # shellcheck disable=SC2002
   cat "$annotation_path" | buildkite-agent annotate --context junit --style error
+
+  if [[ "${BUILDKITE_PLUGIN_JUNIT_ANNOTATE_FAIL_BUILD_ON_ERROR:-false}" =~ (true|on|1) ]]
+  then
+    echo "--- :boom: Failing build due to error"
+    exit 1
+  fi
 fi

plugin.yml

@@ -14,6 +14,8 @@ configuration:
       enum:
         - classname
         - file
+    fail-build-on-error:
+      type: boolean
   required:
     - artifacts
   additionalProperties: false

tests/command.bats

@@ -9,6 +9,7 @@ load "$BATS_PATH/load.bash"
 
 @test "runs the annotator and creates the annotation" {
   export BUILDKITE_PLUGIN_JUNIT_ANNOTATE_ARTIFACTS="junits/*.xml"
+  export BUILDKITE_PLUGIN_JUNIT_ANNOTATE_FAIL_BUILD_ON_ERROR=false
 
   artifacts_tmp="tests/tmp/$PWD/junit-artifacts"
   annotation_tmp="tests/tmp/$PWD/junit-annotation"
@@ -33,10 +34,36 @@ load "$BATS_PATH/load.bash"
   unstub docker
 }
 
+@test "returns an error if fail-build-on-error is true" {
+  export BUILDKITE_PLUGIN_JUNIT_ANNOTATE_ARTIFACTS="junits/*.xml"
+  export BUILDKITE_PLUGIN_JUNIT_ANNOTATE_FAIL_BUILD_ON_ERROR=true
+
+  artifacts_tmp="tests/tmp/$PWD/junit-artifacts"
+  annotation_tmp="tests/tmp/$PWD/junit-annotation"
+
+  stub mktemp \
+    "-d junit-annotate-plugin-artifacts-tmp.XXXXXXXXXX : mkdir -p $artifacts_tmp; echo $artifacts_tmp" \
+    "-d junit-annotate-plugin-annotation-tmp.XXXXXXXXXX : mkdir -p $annotation_tmp; echo $annotation_tmp"
+
+  stub buildkite-agent "artifact download junits/*.xml /plugin/tests/tmp//plugin/junit-artifacts : echo Downloaded artifacts" \
+                       "annotate --context junit --style error : echo Annotation added"
+
+  stub docker "--log-level error run --rm --volume /plugin/tests/tmp//plugin/junit-artifacts:/junits --volume /plugin/hooks/../ruby:/src --env BUILDKITE_PLUGIN_JUNIT_ANNOTATE_JOB_UUID_FILE_PATTERN= --env BUILDKITE_PLUGIN_JUNIT_ANNOTATE_FAILURE_FORMAT= ruby:2.5-alpine /src/bin/annotate /junits : echo '<details>Failure</details>'"
+
+  run "$PWD/hooks/command"
+
+  assert_failure
+
+  unstub mktemp
+  unstub buildkite-agent
+  unstub docker
+}
+
 @test "can pass through optional params" {
   export BUILDKITE_PLUGIN_JUNIT_ANNOTATE_ARTIFACTS="junits/*.xml"
   export BUILDKITE_PLUGIN_JUNIT_ANNOTATE_JOB_UUID_FILE_PATTERN="custom_(*)_pattern.xml"
   export BUILDKITE_PLUGIN_JUNIT_ANNOTATE_FAILURE_FORMAT="file"
+  export BUILDKITE_PLUGIN_JUNIT_ANNOTATE_FAIL_BUILD_ON_ERROR=false
 
   artifacts_tmp="tests/tmp/$PWD/junit-artifacts"
   annotation_tmp="tests/tmp/$PWD/junit-annotation"