Avoid using deprecated depset union

Change-Id: Ifea5bf62dd0a5196e85939eb50e2d43ac551d975
diff --git a/tools/classpath.bzl b/tools/classpath.bzl
index 54f2dd0..55479c5 100644
--- a/tools/classpath.bzl
+++ b/tools/classpath.bzl
@@ -1,13 +1,13 @@
 def _classpath_collector(ctx):
-    all = depset()
+    all = []
     for d in ctx.attr.deps:
         if hasattr(d, "java"):
-            all = all + d.java.transitive_runtime_deps
-            all = all + d.java.compilation_info.runtime_classpath
+            all.append(d.java.transitive_runtime_deps)
+            all.append(d.java.compilation_info.runtime_classpath)
         elif hasattr(d, "files"):
-            all = all + d.files
+            all.append(d.files)
 
-    as_strs = [c.path for c in all.to_list()]
+    as_strs = [c.path for c in depset(transitive = all).to_list()]
     ctx.actions.write(
         output = ctx.outputs.runtime,
         content = "\n".join(sorted(as_strs)),
diff --git a/tools/gwt.bzl b/tools/gwt.bzl
index 65a7d1b..8ae68a4 100644
--- a/tools/gwt.bzl
+++ b/tools/gwt.bzl
@@ -193,17 +193,17 @@
     )
 
 def _get_transitive_closure(ctx):
-    deps = depset()
+    deps = []
     for dep in ctx.attr.module_deps:
-        deps = deps + dep.java.transitive_runtime_deps
-        deps = deps + dep.java.transitive_source_jars
+        deps.append(dep.java.transitive_runtime_deps)
+        deps.append(dep.java.transitive_source_jars)
     for dep in ctx.attr.deps:
         if hasattr(dep, "java"):
-            deps = deps + dep.java.transitive_runtime_deps
+            deps.append(dep.java.transitive_runtime_deps)
         elif hasattr(dep, "files"):
-            deps = deps + dep.files
+            deps.append(dep.files)
 
-    return deps
+    return depset(transitive = deps)
 
 gwt_binary = rule(
     attrs = {
diff --git a/tools/javadoc.bzl b/tools/javadoc.bzl
index 1982b9c..204f569 100644
--- a/tools/javadoc.bzl
+++ b/tools/javadoc.bzl
@@ -17,13 +17,10 @@
 def _impl(ctx):
     zip_output = ctx.outputs.zip
 
-    transitive_jar_set = depset()
-    source_jars = depset()
-    for l in ctx.attr.libs:
-        source_jars = source_jars + l.java.source_jars
-        transitive_jar_set = transitive_jar_set + l.java.transitive_deps
+    transitive_jars = depset(transitive = [l.java.transitive_deps for l in ctx.attr.libs])
+    source_jars = depset(transitive = [l.java.source_jars for l in ctx.attr.libs])
 
-    transitive_jar_paths = [j.path for j in transitive_jar_set.to_list()]
+    transitive_jar_paths = [j.path for j in transitive_jars.to_list()]
     dir = ctx.outputs.zip.path + ".dir"
     source = ctx.outputs.zip.path + ".source"
     external_docs = ["http://docs.oracle.com/javase/8/docs/api"] + ctx.attr.external_docs
@@ -54,7 +51,7 @@
         "(cd %s && zip -qr ../%s *)" % (dir, ctx.outputs.zip.basename),
     ]
     ctx.actions.run_shell(
-        inputs = transitive_jar_set.to_list() + source_jars.to_list() + ctx.files._jdk,
+        inputs = transitive_jars.to_list() + source_jars.to_list() + ctx.files._jdk,
         outputs = [zip_output],
         command = " && ".join(cmd),
     )
diff --git a/tools/pkg_war.bzl b/tools/pkg_war.bzl
index 691b72a..cf65278 100644
--- a/tools/pkg_war.bzl
+++ b/tools/pkg_war.bzl
@@ -56,12 +56,12 @@
         "mkdir -p %s/WEB-INF/lib" % build_output,
     ]
 
-    transitive_lib_deps = depset()
+    transitive_libs = []
     for l in ctx.attr.libs:
         if hasattr(l, "java"):
-            transitive_lib_deps = transitive_lib_deps + l.java.transitive_runtime_deps
+            transitive_libs.append(l.java.transitive_runtime_deps)
         elif hasattr(l, "files"):
-            transitive_lib_deps = transitive_lib_deps + l.files
+            transitive_libs.append(l.files)
 
     for dep in transitive_lib_deps.to_list():
         cmd = cmd + _add_file(ctx.attr.name, dep, build_output + "/WEB-INF/lib/")
@@ -72,13 +72,14 @@
             inputs.append(web_xml)
             cmd = cmd + _add_file(ctx.attr.name, web_xml, build_output + "/WEB-INF/")
 
-    transitive_context_deps = depset()
+    transitive_context_libs = []
     if ctx.attr.context:
         for jar in ctx.attr.context:
             if hasattr(jar, "java"):
-                transitive_context_deps = transitive_context_deps + jar.java.transitive_runtime_deps
+                transitive_context_libs.append(jar.java.transitive_runtime_deps)
             elif hasattr(jar, "files"):
-                transitive_context_deps = transitive_context_deps + jar.files
+                transitive_context_libs.append(jar.files)
+    transitive_context_deps = depset(transitive = transitive_context_libs)
     for dep in transitive_context_deps.to_list():
         cmd = cmd + _add_context(dep, build_output)
         inputs.append(dep)