Enabling missingJavadoc validation in gradle check (#721)

Excludes modules currently failing from missingJavadoc check.
These modules can be removed from exclusion list once javadocs are added.
Currently, only :client:rest module is enabled for missingJavadoc check.
Issue #221 tracks javadocs for legacy code.

These checks are enabled as part of gradle check. Enabling it as part of
precommit needs more work and will be done later.

Once this PR is merged all incoming PRs will undergo javadoc validations.

Signed-off-by: Himanshu Setia <setiah@amazon.com>

gradle/missing-javadoc.gradle

@@ -53,6 +53,10 @@ allprojects {
       docletpath = configurations.missingdoclet
     }
 
+    tasks.withType(Javadoc).configureEach {
+      dependsOn missingJavadoc
+    }
+
 
     tasks.register('missingJavadoc', MissingJavadocTask) {
       description "This task validates and generates Javadoc API documentation for the main source code."
@@ -68,6 +72,110 @@ allprojects {
   }
 }
 
+// Below modules are temporarily excluded for missingJavadoc checks.
+// Currently all these modules fail the check due to missing javadocs.
+// See https://github.com/opensearch-project/OpenSearch/issues/221
+// When you add javadocs for a module, please ensure the missingJavadoc check
+// succeeds after removing that module from below list.
+// You can then remove that module from this exclusion list,
+// which will enforce javadoc validation on it for every incoming PR. For example,
+// the client:rest module has javadoc checks enforced as it is not part of below list.
+// Also different modules might need javadoc validations at different levels,
+// for instance, for some test modules, we may only want to have javadoc at "package"
+// level while for others (like server module) we may want to have it at "parameter" level.
+// Currently everything is configured at parameter level (strictest).
+configure([
+  project(":benchmarks"),
+  project(":build-tools"),
+  project(":build-tools:reaper"),
+  project(":client:benchmark"),
+  project(":client:client-benchmark-noop-api-plugin"),
+  project(":client:rest-high-level"),
+  project(":client:sniffer"),
+  project(":client:test"),
+  project(":client:transport"),
+  project(":distribution:tools:java-version-checker"),
+  project(":distribution:tools:keystore-cli"),
+  project(":distribution:tools:launchers"),
+  project(":distribution:tools:plugin-cli"),
+  project(":doc-tools"),
+  project(":example-plugins:custom-settings"),
+  project(":example-plugins:custom-significance-heuristic"),
+  project(":example-plugins:custom-suggester"),
+  project(":example-plugins:painless-whitelist"),
+  project(":example-plugins:rescore"),
+  project(":example-plugins:rest-handler"),
+  project(":example-plugins:script-expert-scoring"),
+  project(":libs:opensearch-cli"),
+  project(":libs:opensearch-core"),
+  project(":libs:opensearch-dissect"),
+  project(":libs:opensearch-geo"),
+  project(":libs:opensearch-grok"),
+  project(":libs:opensearch-nio"),
+  project(":libs:opensearch-plugin-classloader"),
+  project(":libs:opensearch-secure-sm"),
+  project(":libs:opensearch-ssl-config"),
+  project(":libs:opensearch-x-content"),
+  project(":modules:aggs-matrix-stats"),
+  project(":modules:analysis-common"),
+  project(":modules:geo"),
+  project(":modules:ingest-common"),
+  project(":modules:ingest-geoip"),
+  project(":modules:ingest-user-agent"),
+  project(":modules:lang-expression"),
+  project(":modules:lang-mustache"),
+  project(":modules:lang-painless"),
+  project(":modules:lang-painless:spi"),
+  project(":modules:mapper-extras"),
+  project(":modules:opensearch-dashboards"),
+  project(":modules:parent-join"),
+  project(":modules:percolator"),
+  project(":modules:rank-eval"),
+  project(":modules:reindex"),
+  project(":modules:repository-url"),
+  project(":modules:systemd"),
+  project(":modules:transport-netty4"),
+  project(":plugins:analysis-icu"),
+  project(":plugins:analysis-kuromoji"),
+  project(":plugins:analysis-nori"),
+  project(":plugins:analysis-phonetic"),
+  project(":plugins:analysis-smartcn"),
+  project(":plugins:analysis-stempel"),
+  project(":plugins:analysis-ukrainian"),
+  project(":plugins:discovery-azure-classic"),
+  project(":plugins:discovery-ec2"),
+  project(":plugins:discovery-ec2:qa:amazon-ec2"),
+  project(":plugins:discovery-gce"),
+  project(":plugins:discovery-gce:qa:gce"),
+  project(":plugins:ingest-attachment"),
+  project(":plugins:mapper-annotated-text"),
+  project(":plugins:mapper-murmur3"),
+  project(":plugins:mapper-size"),
+  project(":plugins:repository-azure"),
+  project(":plugins:repository-gcs"),
+  project(":plugins:repository-hdfs"),
+  project(":plugins:repository-s3"),
+  project(":plugins:store-smb"),
+  project(":plugins:transport-nio"),
+  project(":qa:die-with-dignity"),
+  project(":qa:os"),
+  project(":qa:wildfly"),
+  project(":rest-api-spec"),
+  project(":server"),
+  project(":test:external-modules:test-delayed-aggs"),
+  project(":test:fixtures:azure-fixture"),
+  project(":test:fixtures:gcs-fixture"),
+  project(":test:fixtures:hdfs-fixture"),
+  project(":test:fixtures:old-elasticsearch"),
+  project(":test:fixtures:s3-fixture"),
+  project(":test:framework"),
+  project(":test:logger-usage")
+]) {
+  project.tasks.withType(MissingJavadocTask) {
+    isExcluded = true
+  }
+}
+
 class MissingJavadocTask extends DefaultTask {
   @InputFiles
   @SkipWhenEmpty
@@ -94,6 +202,9 @@ class MissingJavadocTask extends DefaultTask {
   @Input
   String javadocMissingLevel = "parameter"
 
+  @Input
+  boolean isExcluded = false
+
   // anything in these packages is checked with level=method. This allows iteratively fixing one package at a time.
   @Input
   List<String> javadocMissingMethod = []
@@ -124,6 +235,10 @@ class MissingJavadocTask extends DefaultTask {
 
   @TaskAction
   void render() {
+    if(isExcluded) {
+      return
+    }
+
     def srcDirs = srcDirSet.srcDirs.findAll { dir -> dir.exists() }
     def optionsFile = project.file("${getTemporaryDir()}/javadoc-options.txt")