Verify JAVA_HOME is set correctly

Our system requirements point that JAVA_HOME must be set, but `tns doctor` is not strict about this.
With version 1.7.0 of the runtime, `jarsigner` from $JAVA_HOME/bin/jarsigner will be called explicitly, so we must be sure JAVA_HOME is correct.
`jarsigner` does not exist in JRE, so add logic to call it in order to verify that the currently set JAVA_HOME is correct.
Validate the information in the following order:
1) Check if JAVA_HOME is set. In case it is not, you cannot build for Android (`tns build android` will fail before starting).
2) Check if JAVA_HOME is correct by executing JAVA_HOME/bin/jarsigner - in case it does not exist - fail
3) Check if the version of the JAVA is correct by calling JAVA_HOME/bin/javac -version and compare it with min required one. In case it's lower - fail.

`tns doctor` will print warning in case any of the above check fails. `tns build android` and any other Android related build operations will fail.

Author: rosen-vladimirov

lib/android-tools-info.ts

@@ -156,30 +156,65 @@ export class AndroidToolsInfo implements IAndroidToolsInfo {
 		}).future<boolean>()();
 	}
 
-	public validateJavacVersion(installedJavaVersion: string, options?: {showWarningsAsErrors: boolean}): IFuture<boolean> {
+	public validateJava(javacVersion: string, options?: {showWarningsAsErrors: boolean}): IFuture<boolean> {
 		return ((): boolean => {
-			let hasProblemWithJavaVersion = false;
 			if(options) {
 				this.showWarningsAsErrors = options.showWarningsAsErrors;
 			}
-			let additionalMessage = "You will not be able to build your projects for Android." + EOL
+
+			let helpfulMessage = "You will not be able to build your projects for Android." + EOL
 				+ "To be able to build for Android, verify that you have installed The Java Development Kit (JDK) and configured it according to system requirements as" + EOL +
 				" described in https://github.com/NativeScript/nativescript-cli#system-requirements.";
-			let matchingVersion = (installedJavaVersion || "").match(AndroidToolsInfo.VERSION_REGEX);
-			if(matchingVersion && matchingVersion[1]) {
-				if(semver.lt(matchingVersion[1], AndroidToolsInfo.MIN_JAVA_VERSION)) {
-					hasProblemWithJavaVersion = true;
-					this.printMessage(`Javac version ${installedJavaVersion} is not supported. You have to install at least ${AndroidToolsInfo.MIN_JAVA_VERSION}.`, additionalMessage);
+
+			let hasProblemWithJavaHome = this.validateJavaHome(helpfulMessage).wait();
+			let hasProblemWithJavaVersion: boolean;
+			if(!hasProblemWithJavaHome) {
+				hasProblemWithJavaVersion = this.validateJavacVersion(javacVersion, helpfulMessage);
+			}
+
+			return hasProblemWithJavaHome || hasProblemWithJavaVersion;
+		}).future<boolean>()();
+	}
+
+	private validateJavaHome(helpfulMessage: string): IFuture<boolean> {
+		return ((): boolean => {
+			let hasProblemWithJavaHome = false;
+			let javaHome = process.env.JAVA_HOME;
+
+			if(javaHome) {
+				// validate jarsigner as it does not exist in JRE, but is mandatory for JDK and Android Runtime
+				let jarSigner = path.join(javaHome, "bin", "jarsigner");
+				let childProcessResult = this.$childProcess.spawnFromEvent(jarSigner, [], "close", {}, { throwError: false }).wait();
+				this.$logger.trace(`Result of calling jarsigner from path: ${jarSigner}:`, childProcessResult);
+				if(childProcessResult.stderr || childProcessResult.exitCode !== 0) {
+					hasProblemWithJavaHome = true;
+					this.printMessage("JAVA_HOME environment variable points to incorrect path. Make sure it points to the installation directory of JDK.", helpfulMessage);
 				}
 			} else {
-				hasProblemWithJavaVersion = true;
-				this.printMessage("Error executing command 'javac'. Make sure you have installed The Java Development Kit (JDK) and set JAVA_HOME environment variable.", additionalMessage);
+				hasProblemWithJavaHome = true;
+				this.printMessage("JAVA_HOME environment variable is not set.", helpfulMessage);
 			}
 
-			return hasProblemWithJavaVersion;
+			return hasProblemWithJavaHome;
 		}).future<boolean>()();
 	}
 
+	private validateJavacVersion(installedJavaVersion: string, helpfulMessage: string): boolean {
+		let hasProblemWithJavaVersion = false;
+		let matchingVersion = (installedJavaVersion || "").match(AndroidToolsInfo.VERSION_REGEX);
+		if(matchingVersion && matchingVersion[1]) {
+			if(semver.lt(matchingVersion[1], AndroidToolsInfo.MIN_JAVA_VERSION)) {
+				hasProblemWithJavaVersion = true;
+				this.printMessage(`Javac version ${installedJavaVersion} is not supported. You have to install at least ${AndroidToolsInfo.MIN_JAVA_VERSION}.`, helpfulMessage);
+			}
+		} else {
+			hasProblemWithJavaVersion = true;
+			this.printMessage("Error executing command 'javac'. Make sure you have installed The Java Development Kit (JDK) and set JAVA_HOME environment variable.", helpfulMessage);
+		}
+
+		return hasProblemWithJavaVersion;
+	}
+
 	public getPathToAdbFromAndroidHome(): IFuture<string> {
 		return (() => {
 			if(this.androidHome) {

lib/declarations.ts

@@ -160,12 +160,12 @@ interface IAndroidToolsInfo {
 	validateInfo(options?: {showWarningsAsErrors: boolean, validateTargetSdk: boolean}): IFuture<boolean>;
 
 	/**
-	 * Validates the information about required JAVA version.
-	 * @param {string} installedJavaVersion The JAVA version that will be checked.
+	 * Validates the information about required JAVA version and JAVA_HOME.
+	 * @param {string} javacVersion The JAVA version that will be checked.
 	 * @param {any} options Defines if the warning messages should treated as error.
 	 * @return {boolean} True if there are detected issues, false otherwise.
 	 */
-	validateJavacVersion(installedJavaVersion: string, options?: {showWarningsAsErrors: boolean}): IFuture<boolean>;
+	validateJava(javacVersion: string, options?: {showWarningsAsErrors: boolean}): IFuture<boolean>;
 
 	/**
 	 * Returns the path to `android` executable. It should be `$ANDROID_HOME/tools/android`.

lib/services/android-project-service.ts

@@ -88,7 +88,7 @@ export class AndroidProjectService extends projectServiceBaseLib.PlatformProject
 
 			// this call will fail in case `android` is not set correctly.
 			this.$androidToolsInfo.getPathToAndroidExecutable({showWarningsAsErrors: true}).wait();
-			this.$androidToolsInfo.validateJavacVersion(this.$sysInfo.getSysInfo(path.join(__dirname, "..", "..", "package.json")).wait().javacVersion, {showWarningsAsErrors: true}).wait();
+			this.$androidToolsInfo.validateJava(this.$sysInfo.getSysInfo(path.join(__dirname, "..", "..", "package.json")).wait().javacVersion, {showWarningsAsErrors: true}).wait();
 		}).future<void>()();
 	}
 

lib/services/doctor-service.ts

@@ -87,7 +87,7 @@ class DoctorService implements IDoctorService {
 		}
 
 		let androidToolsIssues = this.$androidToolsInfo.validateInfo().wait();
-		let javaVersionIssue = this.$androidToolsInfo.validateJavacVersion(sysInfo.javacVersion).wait();
+		let javaVersionIssue = this.$androidToolsInfo.validateJava(sysInfo.javacVersion).wait();
 		return result || androidToolsIssues || javaVersionIssue;
 	}