Bug 1513395 - Ask gradle to download all dependencies. r=nalexander

This adds a task to each project called `downloadDependencies`. This task will
go through each configuration and resolve every dependency so that the gradle
cache contains a copy of every file needed for building and running tests. This
is intended to be used together with our nexus oss database but it can be used
locally too.

Note: `downloadDependencies` does not download dependencies added a runtime,
e.g. by plugins like apilint, checkstyle, findbugs... so we still need to run
those tasks to collect their dependencies.

Depends on D14516

Differential Revision: https://phabricator.services.mozilla.com/D14622

--HG--
extra : moz-landing-system : lando

build.gradle

@@ -40,6 +40,31 @@ allprojects {
             url "file://${gradle.mozconfig.topsrcdir}/mobile/android/gradle/m2repo"
         }
     }
+
+    task downloadDependencies() {
+        description 'Download all dependencies to the Gradle cache'
+        doLast {
+            configurations.each { configuration ->
+                if (configuration.canBeResolved) {
+                    configuration.allDependencies.each { dependency ->
+                        try {
+                            configuration.files(dependency)
+                        } catch(e) {
+                            println("Could not resolve ${configuration.name} -> ${dependency.name}")
+                            println(" > ${e.message}")
+                            if (e.cause) {
+                                println(" >> ${e.cause}")
+                                if (e.cause.cause) {
+                                    println(" >> ${e.cause.cause}")
+                                }
+                            }
+                            println("")
+                        }
+                    }
+                }
+            }
+        }
+    }
 }
 
 buildDir "${topobjdir}/gradle/build"

mobile/android/gradle.configure

@@ -306,18 +306,20 @@ def gradle_android_install_geckoview_example_tasks(build_config):
 set_config('GRADLE_ANDROID_INSTALL_GECKOVIEW_EXAMPLE_TASKS', gradle_android_install_geckoview_example_tasks)
 
 
+@dependable
+def gradle_android_dependencies():
+    '''Gradle tasks that download all dependencies.'''
+    # These tasks download most dependencies from each configuration, the
+    # notable exception is dependencies added at runtime by gradle plugins
+    return [
+        'downloadDependencies',
+    ]
+
 @depends(
-    gradle_android_app_tasks,
     gradle_android_api_lint_tasks,
-    gradle_android_test_tasks,
-    gradle_android_lint_tasks,
     gradle_android_checkstyle_tasks,
     gradle_android_findbugs_tasks,
-    gradle_android_archive_geckoview_tasks,
-    gradle_android_generate_sdk_bindings_tasks,
-    gradle_android_generate_generated_jni_wrappers_tasks,
-    gradle_android_generate_fennec_jni_wrappers_tasks,
-    gradle_android_archive_coverage_artifacts_tasks,
+    gradle_android_dependencies,
 )
 @imports(_from='itertools', _import='imap')
 @imports(_from='itertools', _import='chain')