Index: /trunk/build.xml
===================================================================
--- /trunk/build.xml	(revision 14221)
+++ /trunk/build.xml	(revision 14222)
@@ -40,5 +40,7 @@
         <property name="checkstyle-build.dir" location="${base.dir}/build2"/>
         <property name="epsg.output" location="${base.dir}/data/projection/custom-epsg"/>
-        <property name="error_prone_ant.jar" location="${tools.dir}/error_prone_ant.jar"/>
+        <property name="error_prone_core.jar" location="${tools.dir}/error_prone_core.jar"/>
+        <property name="error_prone_javac.jar" location="${tools.dir}/error_prone_javac.jar"/>
+        <property name="jformatstring.jar" location="${spotbugs.dir}/jFormatString-3.0.0.jar"/>
         <property name="dist.jar" location="${dist.dir}/josm-custom.jar"/>
         <property name="dist-optimized.jar" location="${dist.dir}/josm-custom-optimized.jar"/>
@@ -60,8 +62,4 @@
         <condition property="isJava12"><matches string="${ant.java.version}" pattern="1[2-9]" /></condition>
         <condition property="isJava13"><matches string="${ant.java.version}" pattern="1[3-9]" /></condition>
-        <!-- error_prone works differently on Java 10+, see https://github.com/google/error-prone/issues/860 -->
-        <condition property="javac.compiler" value="modern" else="com.google.errorprone.ErrorProneAntCompilerAdapter">
-            <isset property="isJava10"/>
-        </condition>
         <!-- Disable jacoco on Java 13+, see https://github.com/jacoco/jacoco/pull/738 -->
         <condition property="coverageByDefault">
@@ -87,4 +85,8 @@
                 <include name="*.jar"/>
             </fileset>
+        </path>
+        <path id="processor.path">
+            <pathelement location="${error_prone_core.jar}"/>
+            <pathelement location="${jformatstring.jar}"/>
         </path>
     </target>
@@ -322,12 +324,11 @@
     <target name="compile-jmapviewer" depends="init">
         <!-- JMapViewer -->
-        <javac compiler="${javac.compiler}" sourcepath="" srcdir="${src.dir}" 
+        <javac sourcepath="" srcdir="${src.dir}" fork="yes"
             excludes="com/**,javax/**,oauth/**,org/apache/commons/**,org/glassfish/**,org/openstreetmap/gui/jmapviewer/Demo.java,org/openstreetmap/gui/jmapviewer/JMapViewerTree.java,org/openstreetmap/gui/jmapviewer/checkBoxTree/**,org/openstreetmap/josm/**,org/tukaani/**,gnu/**"
             destdir="${build.dir}" target="${java.lang.version}" source="${java.lang.version}" debug="on" includeantruntime="false" createMissingPackageInfoClass="false" encoding="UTF-8">
-            <compilerclasspath>
-                <pathelement location="${error_prone_ant.jar}"/>
-            </compilerclasspath>
-            <compilerarg line="-XDcompilePolicy=simple" compiler="modern"/>
-            <compilerarg line="-processorpath ${error_prone_ant.jar}" compiler="modern"/>
+            <compilerarg value="-J-Xbootclasspath/p:${error_prone_javac.jar}" unless:set="isJava9"/>
+            <compilerarg line="-XDcompilePolicy=simple"/>
+            <compilerarg value="-processorpath"/>
+            <compilerarg pathref="processor.path"/>
             <compilerarg value="-Xlint:cast"/>
             <compilerarg value="-Xlint:deprecation"/>
@@ -343,8 +344,5 @@
             <!-- Undocumented argument to ignore "Sun internal proprietary API" warning, see http://stackoverflow.com/a/13862308/2257172 -->
             <compilerarg value="-XDignore.symbol.file"/>
-            <compilerarg value="-Xep:CatchAndPrintStackTrace:OFF" compiler="com.google.errorprone.ErrorProneAntCompilerAdapter"/>
-            <compilerarg value="-Xep:ReferenceEquality:OFF" compiler="com.google.errorprone.ErrorProneAntCompilerAdapter"/>
-            <compilerarg value="-Xep:StringSplitter:OFF" compiler="com.google.errorprone.ErrorProneAntCompilerAdapter"/>
-            <compilerarg value="-Xplugin:ErrorProne -Xep:CatchAndPrintStackTrace:OFF -Xep:ReferenceEquality:OFF -Xep:StringSplitter:OFF" compiler="modern"/>
+            <compilerarg value="-Xplugin:ErrorProne -Xep:CatchAndPrintStackTrace:OFF -Xep:ReferenceEquality:OFF -Xep:StringSplitter:OFF"/>
             <compilerarg line="-Xmaxwarns 1000"/>
         </javac>
@@ -352,12 +350,11 @@
     <target name="compile" depends="init,javacc,compile-cots,compile-jmapviewer">
         <!-- JOSM -->
-        <javac compiler="${javac.compiler}" sourcepath="" srcdir="${src.dir}"
+        <javac sourcepath="" srcdir="${src.dir}" fork="yes"
             excludes="com/**,javax/**,gnu/**,oauth/**,org/apache/commons/**,org/glassfish/**,org/openstreetmap/gui/jmapviewer/**,org/tukaani/**"
             destdir="${build.dir}" target="${java.lang.version}" source="${java.lang.version}" debug="on" includeantruntime="false" createMissingPackageInfoClass="false" encoding="UTF-8">
-            <compilerclasspath>
-                <pathelement location="${error_prone_ant.jar}"/>
-            </compilerclasspath>
-            <compilerarg line="-XDcompilePolicy=simple" compiler="modern"/>
-            <compilerarg line="-processorpath ${error_prone_ant.jar}" compiler="modern"/>
+            <compilerarg value="-J-Xbootclasspath/p:${error_prone_javac.jar}" unless:set="isJava9"/>
+            <compilerarg line="-XDcompilePolicy=simple"/>
+            <compilerarg value="-processorpath"/>
+            <compilerarg pathref="processor.path"/>
             <compilerarg value="-Xlint:cast"/>
             <compilerarg value="-Xlint:deprecation"/>
@@ -373,16 +370,5 @@
             <!-- Undocumented argument to ignore "Sun internal proprietary API" warning, see http://stackoverflow.com/a/13862308/2257172 -->
             <compilerarg value="-XDignore.symbol.file"/>
-            <compilerarg value="-Xep:ReferenceEquality:OFF" compiler="com.google.errorprone.ErrorProneAntCompilerAdapter"/>
-            <compilerarg value="-Xep:ImmutableEnumChecker:OFF" compiler="com.google.errorprone.ErrorProneAntCompilerAdapter"/>
-            <compilerarg value="-Xep:FutureReturnValueIgnored:OFF" compiler="com.google.errorprone.ErrorProneAntCompilerAdapter"/>
-            <compilerarg value="-Xep:FloatingPointLiteralPrecision:OFF" compiler="com.google.errorprone.ErrorProneAntCompilerAdapter"/>
-            <compilerarg value="-Xep:ShortCircuitBoolean:OFF" compiler="com.google.errorprone.ErrorProneAntCompilerAdapter"/>
-            <compilerarg value="-Xep:StringSplitter:OFF" compiler="com.google.errorprone.ErrorProneAntCompilerAdapter"/>
-            <compilerarg value="-Xep:JdkObsolete:OFF" compiler="com.google.errorprone.ErrorProneAntCompilerAdapter"/>
-            <compilerarg value="-Xep:UnnecessaryParentheses:OFF" compiler="com.google.errorprone.ErrorProneAntCompilerAdapter"/>
-            <compilerarg value="-Xep:EqualsGetClass:OFF" compiler="com.google.errorprone.ErrorProneAntCompilerAdapter"/>
-            <compilerarg value="-Xep:ThreadPriorityCheck:OFF" compiler="com.google.errorprone.ErrorProneAntCompilerAdapter"/>
-            <compilerarg value="-Xep:UndefinedEquals:OFF" compiler="com.google.errorprone.ErrorProneAntCompilerAdapter"/>
-            <compilerarg value="-Xplugin:ErrorProne -Xep:ReferenceEquality:OFF -Xep:ImmutableEnumChecker:OFF -Xep:FutureReturnValueIgnored:OFF -Xep:FloatingPointLiteralPrecision:OFF -Xep:ShortCircuitBoolean:OFF -Xep:StringSplitter:OFF -Xep:JdkObsolete:OFF -Xep:UnnecessaryParentheses:OFF -Xep:EqualsGetClass:OFF -Xep:ThreadPriorityCheck:OFF -Xep:UndefinedEquals:OFF" compiler="modern"/>
+            <compilerarg value="-Xplugin:ErrorProne -Xep:ReferenceEquality:OFF -Xep:ImmutableEnumChecker:OFF -Xep:FutureReturnValueIgnored:OFF -Xep:FloatingPointLiteralPrecision:OFF -Xep:ShortCircuitBoolean:OFF -Xep:StringSplitter:OFF -Xep:JdkObsolete:OFF -Xep:UnnecessaryParentheses:OFF -Xep:EqualsGetClass:OFF -Xep:ThreadPriorityCheck:OFF -Xep:UndefinedEquals:OFF"/>
             <compilerarg line="-Xmaxwarns 1000"/>
             <exclude name="org/openstreetmap/josm/io/audio/fx/*.java" if:set="noJavaFX"/>
Index: /trunk/src/org/openstreetmap/josm/data/osm/DataSet.java
===================================================================
--- /trunk/src/org/openstreetmap/josm/data/osm/DataSet.java	(revision 14221)
+++ /trunk/src/org/openstreetmap/josm/data/osm/DataSet.java	(revision 14222)
@@ -957,6 +957,6 @@
             if (!eventsToFire.isEmpty()) {
                 lock.readLock().lock();
-                lock.writeLock().unlock();
                 try {
+                    lock.writeLock().unlock();
                     if (eventsToFire.size() < MAX_SINGLE_EVENTS) {
                         for (AbstractDatasetChangedEvent event : eventsToFire) {