From c8e0adbd2af78f43dbc8158970c38eeb41bb5c6c Mon Sep 17 00:00:00 2001
From: Jaikiran Pai <jaikiran@apache.org>
Date: Tue, 19 Mar 2019 13:12:26 +0530
Subject: [PATCH] Use -html4 for javadoc generation

javadoc in our classes don't yet comply to html5 semantics. When
generating javadocs for our project, using JDK 11, we run into
build failures since JDK 11 javadoc tool defaults to html5 output
and is strict if the classes don't comply to the semantics.

The commit here explicitly sets the output to html4 to avoid such
failures, till we fix our javadoc to comply with html5
---
 build.xml | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/build.xml b/build.xml
index 6f7fc08c3..6ea84ef73 100644
--- a/build.xml
+++ b/build.xml
@@ -1503,6 +1503,14 @@
         <patternset refid="useful.tests"/>
       </srcfiles>
     </uptodate>
+    <!-- Javadoc on classes in Ant project, don't (yet) comply to HTML5
+    semantics. javadoc tool in JDK 9+ allows specifying the HTML version
+    to use for the output generation. We intentionally set it to -html4
+    to prevent javadoc tool failures (in JDK 11, which is strict) when
+    running against our code -->
+    <condition property="javadoc.output.htmlversion" value="-html4" else="">
+      <isset property="jdk9+"/>
+    </condition>
   </target>
 
   <target name="javadocs" depends="check-javadoc"
@@ -1535,6 +1543,7 @@
       <group title="Optional Types" packages="org.apache.tools.ant.types.optional*"/>
       <group title="Ant Utilities" packages="org.apache.tools.ant.util*"/>
       <classpath refid="tests-classpath"/>
+      <arg line="${javadoc.output.htmlversion}"/>
     </javadoc>
   </target>