Change dart:io to use Future for one-shot operations.

runtime/bin/process.dart

Index: runtime/bin/process.dart
diff --git a/runtime/bin/process.dart b/runtime/bin/process.dart
index 351465847f6efada58150c04bd14f73ae7b73d22..ac96ef98a4a405ba8a4292fbba0e8b74010ab6fc 100644
--- a/runtime/bin/process.dart
+++ b/runtime/bin/process.dart
@@ -3,47 +3,52 @@
 // BSD-style license that can be found in the LICENSE file.
 
 /**
- * [Process] objects are used to start new processes and interact with
- * them.
+ * [Process] is used to start new processes.
  */
-interface Process default _Process {
+class Process {
   /**
-   * Creates a new process object and starts a process running the
-   * [executable] with the specified [arguments]. When the process has
-   * been successfully started [onStart] is called. If the process
-   * fails to start [onError] is called.
+   * Starts a process running the [executable] with the specified
+   * [arguments]. Returns an [InteractiveProcess] object that can be
+   * used to interact with the process.
    *
    * An optional [ProcessOptions] object can be passed to specify
    * options other than the executable and the arguments.
-   *
-   * No data can be written to the process stdin and the process
-   * cannot be closed nor killed before [onStart] has been invoked.
    */
-  Process.start(String executable,
-                List<String> arguments,
-                [ProcessOptions options]);
+  static InteractiveProcess start(String executable,
+                                  List<String> arguments,
+                                  [ProcessOptions options]) {
+    return _Process.start(executable, arguments, options);
+  }
 
   /**
-   * Creates a new process object, starts a process and runs it
-   * non-interactively to completion. The process run is [executable]
-   * with the specified [arguments]. When the process has been
-   * successfully started [onStart] is called. If the process fails to
-   * start [onError] is called.
+   * Starts a process and runs it non-interactively to completion. The
+   * process run is [executable] with the specified [arguments].
    *
-   * Options other than the executable and the arguments are specified
-   * using a [ProcessOptions] object. If no options are required,
-   * [null] can be passed as the options.
+   * An optional [ProcessOptions] object can be passed to specify
+   * options other than the executable and the arguments.
    *
-   * No communication via [stdin], [stdout] or [stderr] can take place
-   * with a non-interactive process. Instead, the process is run to
-   * completion at which point the exit code and stdout and stderr are
-   * supplied to the [callback] parameter.
-   */
-  Process.run(String executable,
-              List<String> arguments,
-              ProcessOptions options,
-              void callback(int exitCode, String stdout, String stderr));
+   * Returns a [:Future<ProcessResult>:] that completes with the
+   * result of running the process, i.e., exit code, standard out and
+   * standard in.
+   */
+  static Future<ProcessResult> run(String executable,
+                                   List<String> arguments,
+                                   [ProcessOptions options]) {
+    return _Process.run(executable, arguments, options);
+  }
+}
 
+/**
+ * [InteractiveProcess] represents a process which users can
+ * communicate with using streams.
+ *
+ * When the process has been successfully started [onStart] is
+ * called. If the process fails to start [onError] is called.
+ *
+ * No data can be written to the process stdin and the process
+ * cannot be closed nor killed before [onStart] has been invoked.
+ */
+interface InteractiveProcess {
   /**
    * Returns an input stream of the process stdout.
    *
@@ -108,6 +113,28 @@ interface Process default _Process {
 
 
 /**
+ * [ProcessResult] represents the result of running a non-interactive
+ * process started with [:Process.run:].
+ */
+interface ProcessResult {
+  /**
+   * Exit code for the process.
+   */
+  int get exitCode();
+
+  /**
+   * Standard output from the process as a string.
+   */
+  String get stdout();
+
+  /**
+   * Standard error from the process as a string.
+   */
+  String get stderr();
+}
+
+
+/**
  * [ProcessOptions] represents the options that can be supplied when
  * starting a process.
  */
@@ -156,7 +183,7 @@ class ProcessOptions {
 
 class ProcessException implements Exception {
   const ProcessException([String this.message, int this.errorCode = 0]);
-  String toString() => "ProcessException: $message";
+  String toString() => "ProcessException: $message ($errorCode)";
 
   /**
    * Contains the system message for the process exception if any.