taskgraph: Speed up gradle calls

app/build.gradle

@@ -549,21 +549,20 @@ if (project.hasProperty("coverage")) {
 
 // -------------------------------------------------------------------------------------------------
 // Task for printing APK information for the requested variant
-// Usage: "./gradlew printVariant -PvariantBuildType=nightly -PvariantEngine=geckoNightly"
+// Usage: "./gradlew printVariants
 // -------------------------------------------------------------------------------------------------
-task printVariant {
+task printVariants {
     doLast {
-        def rawVariant = android.applicationVariants.find {
-            it.buildType.name == variantBuildType &&
-                    it.productFlavors.find { it.dimension == 'engine' }.name == variantEngine
-        }
-        println 'variant: ' + groovy.json.JsonOutput.toJson([
-            name: rawVariant.name,
-            apks: rawVariant.variantData.outputScope.apkDatas.collect { [
-                    abi: it.filters.find { it.filterType == 'ABI' }.identifier,
-                    fileName: it.outputFileName,
-            ]}
-        ])
+        def variants = android.applicationVariants.collect {[
+            apks: it.variantData.outputScope.apkDatas.collect {[
+                abi: it.filters.find { it.filterType == 'ABI' }.identifier,
+                fileName: it.outputFileName,
+            ]},
+            build_type: it.buildType.name,
+            engine: it.productFlavors.find { it.dimension == 'engine' }.name,
+            name: it.name,
+        ]}
+        println 'variants: ' + groovy.json.JsonOutput.toJson(variants)
     }
 }
 

taskcluster/fenix_taskgraph/gradle.py

@@ -10,10 +10,30 @@ import subprocess
 from taskgraph.util.memoize import memoize
 
 
-@memoize
+
 def get_variant(build_type, engine):
-    output = _run_gradle_process('printVariant', variantBuildType=build_type, variantEngine=engine)
-    content = _extract_content_from_command_output(output, prefix='variant: ')
+    all_variants = _fetch_all_variants()
+    matching_variants = [
+        variant for variant in all_variants
+        if variant["build_type"] == build_type and variant["engine"] == engine
+    ]
+    number_of_matching_variants = len(matching_variants)
+    if number_of_matching_variants == 0:
+        raise ValueError('No variant found for build type "{}" and engine "{}"'.format(
+            build_type, engine
+        ))
+    elif number_of_matching_variants > 1:
+        raise ValueError('Too many variants found for build type "{}" and engine "{}": {}'.format(
+            build_type, engine, matching_variants
+        ))
+
+    return matching_variants.pop()
+
+
+@memoize
+def _fetch_all_variants():
+    output = _run_gradle_process('printVariants')
+    content = _extract_content_from_command_output(output, prefix='variants: ')
     return json.loads(content)