Port DocsTest gradle plugin to java (#107124)

* Refactor DocsTest plugin to java
* Rework asciidoc parsing to make adding more parser simple

build-tools-internal/src/integTest/groovy/org/elasticsearch/gradle/internal/doc/DocsTestPluginFuncTest.groovy

@@ -0,0 +1,132 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License
+ * 2.0 and the Server Side Public License, v 1; you may not use this file except
+ * in compliance with, at your election, the Elastic License 2.0 or the Server
+ * Side Public License, v 1.
+ */
+
+package org.elasticsearch.gradle.internal.doc
+
+import org.elasticsearch.gradle.fixtures.AbstractGradleInternalPluginFuncTest
+import org.elasticsearch.gradle.internal.conventions.precommit.PrecommitPlugin
+import org.gradle.testkit.runner.TaskOutcome
+
+class DocsTestPluginFuncTest extends AbstractGradleInternalPluginFuncTest {
+    Class<? extends PrecommitPlugin> pluginClassUnderTest = DocsTestPlugin.class
+
+    def setup() {
+        File docDir = new File(projectDir, 'doc');
+        docDir.mkdirs()
+        addSampleDoc(docDir)
+        buildApiRestrictionsDisabled = true
+    configurationCacheCompatible = false;
+        buildFile << """
+tasks.named('listSnippets') {
+   docs = fileTree('doc')
+}
+
+tasks.named('listConsoleCandidates') {
+   docs = fileTree('doc')
+}
+"""
+    }
+
+    def "can list snippets"() {
+        when:
+        def result = gradleRunner("listSnippets").build()
+        then:
+        result.task(":listSnippets").outcome == TaskOutcome.SUCCESS
+        assertOutputContains(result.output, """
+> Task :listSnippets
+mapper-annotated-text.asciidoc[37:39](Painless)
+mapper-annotated-text.asciidoc[42:44](js)
+mapper-annotated-text.asciidoc[51:69](console)// TEST[setup:seats]
+""")
+    }
+
+    def "can console candidates"() {
+        when:
+        def result = gradleRunner("listConsoleCandidates").build()
+        then:
+        result.task(":listConsoleCandidates").outcome == TaskOutcome.SUCCESS
+        assertOutputContains(result.output, """
+> Task :listConsoleCandidates
+mapper-annotated-text.asciidoc[42:44](js)
+""")
+    }
+
+    void addSampleDoc(File docFolder) {
+        new File(docFolder, "mapper-annotated-text.asciidoc").text = """
+[[painless-filter-context]]
+=== Filter context
+
+Use a Painless script as a {ref}/query-dsl-script-query.html[filter] in a
+query to include and exclude documents.
+
+
+*Variables*
+
+`params` (`Map`, read-only)::
+        User-defined parameters passed in as part of the query.
+
+`doc` (`Map`, read-only)::
+        Contains the fields of the current document where each field is a
+        `List` of values.
+
+*Return*
+
+`boolean`::
+        Return `true` if the current document should be returned as a result of
+        the query, and `false` otherwise.
+
+
+*API*
+
+The standard <<painless-api-reference-shared, Painless API>> is available.
+
+*Example*
+
+To run this example, first follow the steps in
+<<painless-context-examples, context examples>>.
+
+This script finds all unsold documents that cost less than \$25.
+
+[source,Painless]
+----
+doc['sold'].value == false && doc['cost'].value < 25
+----
+
+[source,js]
+----
+curl 'hello world'
+----
+
+Defining `cost` as a script parameter enables the cost to be configured
+in the script query request. For example, the following request finds
+all available theatre seats for evening performances that are under \$25.
+
+[source,console]
+----
+GET seats/_search
+{
+  "query": {
+    "bool": {
+      "filter": {
+        "script": {
+          "script": {
+            "source": "doc['sold'].value == false && doc['cost'].value < params.cost",
+            "params": {
+              "cost": 25
+            }
+          }
+        }
+      }
+    }
+  }
+}
+----
+// TEST[setup:seats]
+"""
+    }
+}