Add 'mach check' and 'mach check-geckolib'

README.md

@@ -133,7 +133,6 @@ Mach tools to orchestrate the build and other tasks.
 
 ### Normal build
 
-
 To build Servo in development mode.  This is useful for development, but
 the resulting binary is very slow.
 
@@ -159,6 +158,20 @@ real-world use, add the `--release` flag to create an optimized build:
 ./mach run --release tests/html/about-mozilla.html
 ```
 
+### Checking for build errors, without building
+
+If you’re making changes to one crate that cause build errors in another crate,
+consider this instead of a full build:
+
+```sh
+./mach check
+```
+
+It will run `cargo check`, which runs the analysis phase of the compiler
+(and so shows build errors if any) but skips the code generation phase.
+This can be a lot faster than a full build,
+though of course it doesn’t produce a binary you can run.
+
 ### Building for Android target
 
 ``` sh

python/servo/devenv_commands.py

@@ -9,6 +9,7 @@
 
 from __future__ import print_function, unicode_literals
 from os import path, getcwd, listdir
+from time import time
 
 import sys
 import urllib2
@@ -21,10 +22,43 @@ from mach.decorators import (
 )
 
 from servo.command_base import CommandBase, cd, call
+from servo.build_commands import notify_build_done
 
 
 @CommandProvider
 class MachCommands(CommandBase):
+    def run_cargo(self, params, geckolib=False, check=False):
+        if geckolib:
+            self.set_use_stable_rust()
+            crate_dir = path.join('ports', 'geckolib')
+        else:
+            crate_dir = path.join('components', 'servo')
+
+        self.ensure_bootstrapped()
+        self.ensure_clobbered()
+        env = self.build_env(geckolib=geckolib)
+
+        if not params:
+            params = []
+
+        if check:
+            params = ['check'] + params
+
+        build_start = time()
+        if self.context.topdir == getcwd():
+            with cd(crate_dir):
+                status = call(['cargo'] + params, env=env)
+        else:
+            status = call(['cargo'] + params, env=env)
+        elapsed = time() - build_start
+
+        notify_build_done(self.config, elapsed, status == 0)
+
+        if check and status == 0:
+            print('Finished checking, binary NOT updated. Consider ./mach build before ./mach run')
+
+        return status
+
     @Command('cargo',
              description='Run Cargo',
              category='devenv')
@@ -32,15 +66,7 @@ class MachCommands(CommandBase):
         'params', default=None, nargs='...',
         help="Command-line arguments to be passed through to Cargo")
     def cargo(self, params):
-        if not params:
-            params = []
-
-        self.ensure_bootstrapped()
-
-        if self.context.topdir == getcwd():
-            with cd(path.join('components', 'servo')):
-                return call(["cargo"] + params, env=self.build_env())
-        return call(['cargo'] + params, env=self.build_env())
+        return self.run_cargo(params)
 
     @Command('cargo-geckolib',
              description='Run Cargo with the same compiler version and root crate as build-geckolib',
@@ -49,17 +75,25 @@ class MachCommands(CommandBase):
         'params', default=None, nargs='...',
         help="Command-line arguments to be passed through to Cargo")
     def cargo_geckolib(self, params):
-        if not params:
-            params = []
+        return self.run_cargo(params, geckolib=True)
 
-        self.set_use_stable_rust()
-        self.ensure_bootstrapped()
-        env = self.build_env(geckolib=True)
+    @Command('check',
+             description='Run "cargo check"',
+             category='devenv')
+    @CommandArgument(
+        'params', default=None, nargs='...',
+        help="Command-line arguments to be passed through to cargo check")
+    def check(self, params):
+        return self.run_cargo(params, check=True)
 
-        if self.context.topdir == getcwd():
-            with cd(path.join('ports', 'geckolib')):
-                return call(["cargo"] + params, env=env)
-        return call(['cargo'] + params, env=env)
+    @Command('check-geckolib',
+             description='Run "cargo check" with the same compiler version and root crate as build-geckolib',
+             category='devenv')
+    @CommandArgument(
+        'params', default=None, nargs='...',
+        help="Command-line arguments to be passed through to cargo check")
+    def check_geckolib(self, params):
+        return self.run_cargo(params, check=True, geckolib=True)
 
     @Command('cargo-update',
              description='Same as update-cargo',