chore: Add CI check for method/constructor Javadoc quality

.github/workflows/tests.yml

@@ -109,6 +109,8 @@ jobs:
     name: Extra checks
     steps:
       - uses: actions/checkout@5a4ac9002d0be2fb38bd78e4b4dbde5606d7042f # v2.3.4
+        with:
+          fetch-depth: 0
       - uses: actions/setup-java@8764a52df183aa0ccea74521dfd9d506ffc7a19a # v2.0.0
         with:
           java-version: 15
@@ -132,6 +134,8 @@ jobs:
         run: mv chore/logback.xml src/test/resources/
       - name: Run extra checks
         run: ./chore/ci-extra.sh
+      - name: Run Javadoc quality check
+        run: ./chore/ci-checkstyle-javadoc.sh
 
   sorald-buildbreaker:
     runs-on: ubuntu-latest

chore/ci-checkstyle-javadoc.sh

@@ -0,0 +1,77 @@
+#!/bin/bash
+#
+# This script computes the amount of method Javadoc errors found by
+# checkstyle and compares with the master branch. If the amount of
+# errors have increased relative to master, it exits non-zero.
+#
+# WARNING: Running this script resets the state of the repository to the
+# latest commit, do NOT run this locally if you have any uncommitted changes.
+
+set -o errexit
+set -o nounset
+set -o pipefail
+
+COMPARE_BRANCH="master"
+JAVADOC_CHECKSTYLE_CONFIG="__SPOON_CI_checkstyle-javadoc.xml"
+
+if [[ $(git branch --show-current) == "$COMPARE_BRANCH" ]]; then
+    # nothing to compare, we're on the main branch
+    exit 0
+fi
+
+function cleanup() {
+    rm "$JAVADOC_CHECKSTYLE_CONFIG"
+}
+
+trap cleanup EXIT
+
+function create_checkstyle_config() {
+    echo '<?xml version="1.0"?>
+<!DOCTYPE module PUBLIC "-//Puppy Crawl//DTD Check Configuration 1.2//EN" "http://www.puppycrawl.com/dtds/configuration_1_2.dtd">
+<module name="Checker">
+  <module name="TreeWalker">
+    <module name="JavadocMethod">
+      <property name="scope" value="public"/>
+    </module>
+  </module>
+</module>' > "$JAVADOC_CHECKSTYLE_CONFIG"
+}
+
+function compute_num_errors() {
+    echo $(mvn -B checkstyle:check --fail-never -Dcheckstyle.config.location="$JAVADOC_CHECKSTYLE_CONFIG" \
+        | grep -Po '(?<=There are )\d+(?= errors reported by Checkstyle)')
+}
+
+function main() {
+    cd "$(git rev-parse --show-toplevel)"
+
+    # compute compare score
+    git checkout --force "$COMPARE_BRANCH" &> /dev/null
+    create_checkstyle_config
+    compare_num_errors=`compute_num_errors`
+
+    # compute current score
+    git checkout --force - &> /dev/null
+    create_checkstyle_config
+    current_num_errors=`compute_num_errors`
+
+    echo "JAVADOC QUALITY SCORE (lower is better)
+    Compare: $compare_num_errors
+    Current: $current_num_errors
+    "
+
+    if [[ -z $compare_num_errors ]]; then
+        echo "Failed to compute compare score";
+        exit 1;
+    elif [[ -z $current_num_errors ]]; then
+        echo "Failed to compute current score";
+        exit 1;
+    elif [[ $compare_num_errors < $current_num_errors ]]; then
+        echo "Javadoc quality has deteriorated!"
+        exit 1
+    else
+        echo "Javadoc quality has not deteriorated"
+    fi
+}
+
+main