[gnome-builder] cargo: implement build target provider

[Christian Hergert <chergert src gnome org>]

commit dd0acd95f585e16a0191971ea7351adfddc29d34
Author: Christian Hergert <chergert redhat com>
Date:   Wed Nov 22 16:49:18 2017 -0800

    cargo: implement build target provider
    
    Implement the basics for the build target provider in cargo. We
    still need to propagate the directory for which it must be
    run as, so that cargo can find the proper information.

 src/plugins/cargo/cargo_plugin.py |   48 +++++++++++++++++++++++++++++++++++++
 1 files changed, 48 insertions(+), 0 deletions(-)
---
diff --git a/src/plugins/cargo/cargo_plugin.py b/src/plugins/cargo/cargo_plugin.py
index abf501a..c49b563 100644
--- a/src/plugins/cargo/cargo_plugin.py
+++ b/src/plugins/cargo/cargo_plugin.py
@@ -149,3 +149,51 @@ class CargoPipelineAddin(Ide.Object, Ide.BuildPipelineAddin):
         build_stage.set_clean_launcher(clean_launcher)
         self.track(pipeline.connect(Ide.BuildPhase.BUILD, 0, build_stage))
 
+class CargoBuildTarget(Ide.Object, Ide.BuildTarget):
+
+    def do_get_install_directory(self):
+        return None
+
+    def do_get_name(self):
+        return 'cargo-run'
+
+    def do_get_argv(self):
+        context = self.get_context()
+        config_manager = context.get_configuration_manager()
+        config = config_manager.get_current()
+        cargo = locate_cargo_from_config(config)
+
+        # Pass the Cargo.toml path so that we don't
+        # need to run from the project directory.
+        project_file = context.get_project_file()
+        if project_file.get_basename() == 'Cargo.toml':
+            cargo_toml = project_file.get_path()
+        else:
+            cargo_toml = project_file.get_child('Cargo.toml')
+
+        return [cargo, 'run', '--manifest-path', cargo_toml]
+
+    def do_get_priority(self):
+        return 0
+
+class CargoBuildTargetProvider(Ide.Object, Ide.BuildTargetProvider):
+
+    def do_get_targets_async(self, cancellable, callback, data):
+        task = Gio.Task.new(self, cancellable, callback)
+        task.set_priority(GLib.PRIORITY_LOW)
+
+        context = self.get_context()
+        build_system = context.get_build_system()
+
+        if type(build_system) != CargoBuildSystem:
+            task.return_error(GLib.Error('Not cargo build system',
+                                         domain=GLib.quark_to_string(Gio.io_error_quark()),
+                                         code=Gio.IOErrorEnum.NOT_SUPPORTED))
+            return
+
+        task.targets = [CargoBuildTarget(context=self.get_context())]
+        task.return_boolean(True)
+
+    def do_get_targets_finish(self, result):
+        if result.propagate_boolean():
+            return result.targets