Lazily resolve the hermesc path rather than eagerly

Summary:
This commit moves the resolution of the hermesc inside the TaskAction block of the
HermesBinaryTask. Therefore the hermesc path will be investigated only during the
execution of the task, and not when the task is created.

Changelog:
[Internal] [Changed] - Lazily resolve the hermesc path rather than eagerly

Reviewed By: motiz88

Differential Revision: D35930548

fbshipit-source-id: a517dda0fa9b10f53c25cd256ceb68d37d533d3b

packages/react-native-gradle-plugin/src/main/kotlin/com/facebook/react/TaskConfiguration.kt

@@ -15,7 +15,6 @@ import com.facebook.react.tasks.BundleJsAndAssetsTask
 import com.facebook.react.tasks.HermesBinaryTask
 import com.facebook.react.utils.detectedCliPath
 import com.facebook.react.utils.detectedEntryFile
-import com.facebook.react.utils.detectedHermesCommand
 import java.io.File
 import org.gradle.api.Project
 import org.gradle.api.Task
@@ -95,8 +94,8 @@ internal fun Project.configureReactTasks(variant: BaseVariant, config: ReactExte
         it.group = REACT_GROUP
         it.description = "bundle hermes resources for $targetName"
 
-        it.reactRoot = config.root.get().asFile
-        it.hermesCommand = detectedHermesCommand(config)
+        it.root = config.root.get().asFile
+        it.hermesCommand = config.hermesCommand.get()
         it.hermesFlags = config.hermesFlagsForVariant(variant)
         it.jsBundleFile = jsBundleFile
         it.composeSourceMapsCommand = nodeExecutableAndArgs + config.composeSourceMapsPath.get()

packages/react-native-gradle-plugin/src/main/kotlin/com/facebook/react/tasks/HermesBinaryTask.kt

@@ -7,6 +7,7 @@
 
 package com.facebook.react.tasks
 
+import com.facebook.react.utils.detectOSAwareHermesCommand
 import com.facebook.react.utils.moveTo
 import com.facebook.react.utils.windowsAwareCommandLine
 import java.io.File
@@ -19,7 +20,7 @@ import org.gradle.api.tasks.TaskAction
 
 open class HermesBinaryTask : DefaultTask() {
 
-  @get:Internal internal lateinit var reactRoot: File
+  @get:Internal internal lateinit var root: File
 
   @get:Input internal lateinit var hermesCommand: String
   @get:Input internal var hermesFlags: List<String> = emptyList()
@@ -33,8 +34,9 @@ open class HermesBinaryTask : DefaultTask() {
 
   @TaskAction
   fun run() {
+    val detectedHermesCommand = detectOSAwareHermesCommand(root, hermesCommand)
     val bytecodeTempFile = File("$jsBundleFile.hbc")
-    emitHermesBinary(outputFile = bytecodeTempFile)
+    emitHermesBinary(hermesCommand = detectedHermesCommand, outputFile = bytecodeTempFile)
     bytecodeTempFile.moveTo(jsBundleFile)
 
     if (hermesFlags.contains("-output-source-map")) {
@@ -44,7 +46,7 @@ open class HermesBinaryTask : DefaultTask() {
     }
   }
 
-  private fun emitHermesBinary(outputFile: File) {
+  private fun emitHermesBinary(hermesCommand: String, outputFile: File) {
     project.exec {
       @Suppress("SpreadOperator")
       it.commandLine(
@@ -60,7 +62,7 @@ open class HermesBinaryTask : DefaultTask() {
 
   private fun composeSourceMaps() {
     project.exec {
-      it.workingDir(reactRoot)
+      it.workingDir(root)
 
       @Suppress("SpreadOperator")
       it.commandLine(

packages/react-native-gradle-plugin/src/main/kotlin/com/facebook/react/utils/PathUtils.kt

@@ -112,8 +112,16 @@ private fun detectCliPath(
           "This file typically resides in `node_modules/react-native/cli.js`")
 }
 
-// Make sure not to inspect the Hermes config unless we need it,
-// to avoid breaking any JSC-only setups.
+/**
+ * Computes the `hermesc` command location. The Algo follows this order:
+ * 1. The path provided by the `hermesCommand` config in the `react` Gradle extension
+ * 2. The file located in `node_modules/react-native/sdks/hermes/build/bin/hermesc`. This will be
+ * used if the user is building Hermes from source.
+ * 3. The file located in `node_modules/react-native/sdks/hermesc/%OS-BIN%/hermesc` where `%OS-BIN%`
+ * is substituted with the correct OS arch. This will be used if the user is using a precompiled
+ * hermes-engine package.
+ * 4. Fails otherwise
+ */
 internal fun detectOSAwareHermesCommand(projectRoot: File, hermesCommand: String): String {
   // 1. If the project specifies a Hermes command, don't second guess it.
   if (hermesCommand.isNotBlank()) {

packages/react-native-gradle-plugin/src/test/kotlin/com/facebook/react/utils/PathUtilsTest.kt

@@ -142,24 +142,6 @@ class PathUtilsTest {
     detectedCliPath(project.projectDir, extension)
   }
 
-  @Test
-  fun detectedHermesCommand_withPathFromExtension() {
-    val extension = TestReactExtension(ProjectBuilder.builder().build())
-    val expected = tempFolder.newFile("hermesc")
-    extension.hermesCommand.set(expected.toString())
-
-    val actual = detectedHermesCommand(extension)
-
-    assertEquals(expected.toString(), actual)
-  }
-
-  @Test(expected = IllegalStateException::class)
-  fun detectedHermesCommand_failsIfNotFound() {
-    val extension = TestReactExtension(ProjectBuilder.builder().build())
-
-    val actual = detectedHermesCommand(extension)
-  }
-
   @Test
   fun projectPathToLibraryName_withSimplePath() {
     assertEquals("SampleSpec", projectPathToLibraryName(":sample"))