CommandException to cleanly exit product-config on error.

Test: none
Change-Id: I06bb80fe1cc21d77ca3e32ac3110a08fc8b5af54

tools/product_config/src/com/android/build/config/CommandException.java

@@ -0,0 +1,39 @@
+/*
+ * Copyright (C) 2020 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.build.config;
+
+/**
+ * Exception to indicate that a fatal error has occurred.  Throwing this
+ * will cause errors to be printed, cleanup to occur, and the command to
+ * exit with a failure code.
+ *
+ * These are user errors. Throwing other exceptions will result in
+ * the stack trace being shown.
+ */
+public class CommandException extends RuntimeException {
+    public CommandException() {
+        super();
+    }
+
+    public CommandException(String message) {
+        super(message);
+    }
+
+    public CommandException(String message, Throwable chain) {
+        super(message, chain);
+    }
+}

tools/product_config/src/com/android/build/config/Main.java

@@ -38,27 +38,45 @@ public class Main {
 
         // TODO: Get the variables that were defined in starlark and use that to write
         // out the make, soong and bazel input files.
+        mErrors.add(mErrors.ERROR_COMMAND_LINE, "asdf");
+        throw new RuntimeException("poop");
     }
 
     public static void main(String[] args) {
         Errors errors = new Errors();
+        int exitCode = 0;
 
-        Options options = Options.parse(errors, args);
-        if (errors.hadError()) {
-            Options.printHelp(System.err);
+        try {
+            Options options = Options.parse(errors, args);
+            if (errors.hadError()) {
+                Options.printHelp(System.err);
+                System.err.println();
+                throw new CommandException();
+            }
+
+            switch (options.getAction()) {
+                case DEFAULT:
+                    (new Main(errors, options)).run();
+                    return;
+                case HELP:
+                    Options.printHelp(System.out);
+                    return;
+            }
+        } catch (CommandException ex) {
+            // These are user errors, so don't show a stack trace
+            exitCode = 1;
+        } catch (Throwable ex) {
+            // These are programming errors in the code of this tool, so print the exception.
+            // We'll try to print this.  If it's something unrecoverable, then we'll hope
+            // for the best. We will still print the errors below, because they can be useful
+            // for debugging.
+            ex.printStackTrace(System.err);
             System.err.println();
+            exitCode = 1;
+        } finally {
+            // Print errors and warnings
             errors.printErrors(System.err);
-            System.exit(1);
-        }
-
-        switch (options.getAction()) {
-            case DEFAULT:
-                (new Main(errors, options)).run();
-                errors.printErrors(System.err);
-                return;
-            case HELP:
-                Options.printHelp(System.out);
-                return;
         }
+        System.exit(exitCode);
     }
 }