Prepare Javadoc for Java 11, and make other improvements:

- Move nearly all Javadoc configuration to the parent POM.
- Update Guava and ICU4J link locations. The current links resolve to the Javadoc -- but only after a redirect, which Javadoc doesn't like: https://bugs.openjdk.java.net/browse/JDK-8190312
- Update maven-javadoc-plugin to 3.1.1. (This version knows how to work around the aforementioned redirect problem, should it happen again.)
- Add links to Checker Framework. For some reason, this isn't working under Java 11. I haven't investigated.
- Disable detectJavaApiLink, and fill in https://docs.oracle.com/javase/9/docs/api/ for Java 8 and https://docs.oracle.com/en/java/javase/11/docs/api/ for newer versions. (I've tested only with Java 8 and 11, so hopefully the "newer versions" behavior is OK for 9 and 10.)
  It does look like it may be necessary to duplicate all the links in 3 places :\
  This is all in service of preventing:
    [ERROR] Exit code: 1 - javadoc: error - The code being documented uses modules but the packages defined in https://docs.oracle.com/javase/9/docs/api/ are in the unnamed module.
  Traditionally we solve this problem by setting <source>8</source> on Javadoc (CL 235241314, CL 236159968). That would probably work here, but I've been experimenting with <source>9</source> (for proper modules support in jimfs), so that might not be an option soon. Or maybe it still would be, but I'd have to exclude module-info.java, but then I wonder if that will trigger modules problems? In any case, it seems more future-proof to solve this the right(?) way.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=272937179

2 files changed, 44 insertions, 11 deletions

diff --git a/jimfs/pom.xml b/jimfs/pom.xml
index 6c8f9c8..d4b5ba1 100644
--- a/jimfs/pom.xml
+++ b/jimfs/pom.xml
@@ -99,15 +99,7 @@
       <plugin>
         <artifactId>maven-javadoc-plugin</artifactId>
         <configuration>
-          <encoding>UTF-8</encoding>
-          <docencoding>UTF-8</docencoding>
-          <charset>UTF-8</charset>
           <excludePackageNames>com.google.jimfs.internal</excludePackageNames>
-          <links>
-            <link>http://google.github.io/guava/releases/${guava.version}/api/docs/</link>
-            <link>http://icu-project.org/apiref/icu4j/</link>
-            <link>https://docs.oracle.com/javase/9/docs/api/</link>
-          </links>
         </configuration>
         <executions>
           <execution>
diff --git a/pom.xml b/pom.xml
index ee296a6..4900945 100644
--- a/pom.xml
+++ b/pom.xml
@@ -167,7 +167,21 @@
         </plugin>
         <plugin>
           <artifactId>maven-javadoc-plugin</artifactId>
-          <version>3.0.0</version>
+          <version>3.1.1</version>
+          <configuration>
+            <debug>true</debug>
+            <encoding>UTF-8</encoding>
+            <docencoding>UTF-8</docencoding>
+            <charset>UTF-8</charset>
+            <detectJavaApiLink>false</detectJavaApiLink>
+            <links>
+              <link>https://checkerframework.org/api/</link>
+              <link>https://guava.dev/releases/${guava.version}/api/docs/</link>
+              <link>https://unicode-org.github.io/icu-docs/apidoc/released/icu4j</link>
+              <!-- When building against Java 8, the Java 11 link below is overridden to point to an older version (Java 9, the newest one that works). -->
+              <link>https://docs.oracle.com/en/java/javase/11/docs/api/</link>
+            </links>
+          </configuration>
         </plugin>
         <plugin>
           <artifactId>maven-gpg-plugin</artifactId>
@@ -242,7 +256,6 @@
       <reporting>
         <plugins>
           <plugin>
-            <groupId>org.apache.maven.plugins</groupId>
             <artifactId>maven-javadoc-plugin</artifactId>
             <configuration>
               <additionalOptions>
@@ -255,7 +268,6 @@
       <build>
         <plugins>
           <plugin>
-            <groupId>org.apache.maven.plugins</groupId>
             <artifactId>maven-javadoc-plugin</artifactId>
             <configuration>
               <additionalOptions>
@@ -274,8 +286,25 @@
       <activation>
         <jdk>1.8</jdk>
       </activation>
+      <reporting>
+        <plugins>
+          <plugin>
+            <artifactId>maven-javadoc-plugin</artifactId>
+            <configuration>
+              <links>
+                <link>https://checkerframework.org/api/</link>
+                <link>https://guava.dev/releases/${guava.version}/api/docs/</link>
+                <link>https://unicode-org.github.io/icu-docs/apidoc/released/icu4j</link>
+                <link>https://docs.oracle.com/javase/9/docs/api/</link>
+              </links>
+            </configuration>
+          </plugin>
+        </plugins>
+      </reporting>
       <build>
         <plugins>
+          <!-- https://errorprone.info/docs/installation#maven -->
+          <!-- using github.com/google/error-prone-javac is required when running on JDK 8 -->
           <plugin>
             <groupId>org.apache.maven.plugins</groupId>
             <artifactId>maven-compiler-plugin</artifactId>
@@ -286,6 +315,18 @@
               </compilerArgs>
             </configuration>
           </plugin>
+
+          <plugin>
+            <artifactId>maven-javadoc-plugin</artifactId>
+            <configuration>
+              <links>
+                <link>https://checkerframework.org/api/</link>
+                <link>https://guava.dev/releases/${guava.version}/api/docs/</link>
+                <link>https://unicode-org.github.io/icu-docs/apidoc/released/icu4j</link>
+                <link>https://docs.oracle.com/javase/9/docs/api/</link>
+              </links>
+            </configuration>
+          </plugin>
         </plugins>
       </build>
     </profile>