refactor(package-managers): select the package manager and resolve packages synchronously

Nothing about locating an installed package is asynchronous; the only
async link was the dispatcher reading the "packageManager" user setting
through the settings lock. JsonFileSettingsService gains a lock-free
getSettingValueSync for settings that only change through explicit user
commands, and the dispatcher now picks its implementation lazily and
synchronously, dropping the @cache/@invokeInit init dance.

getInstalledPackagePath is therefore synchronous on the contract, which
unwinds the async that had been threaded through doctor, plugins-service,
the bundler, the test runners, preview and android-plugin-build-service,
and lets the last two direct users of the resolution helper move onto the
contract: getRuntimePackage in project-data-service (resolved lazily via
the injector, as the service is constructed everywhere) and the transitive
walk in node-modules-dependencies-builder.

Author: rigor789

PublicAPI.md

@@ -579,16 +579,15 @@ Locates a package the way the selected package manager laid it out on disk, so c
 /**
  * @param  {string} packageName The name of the package.
  * @param  {string} fromDir     The directory whose dependencies are searched, usually the project directory.
- * @return {Promise<string>} The absolute path of the package directory, or null when it is not installed.
+ * @return {string} The absolute path of the package directory, or null when it is not installed.
  */
-getInstalledPackagePath(packageName: string, fromDir: string): Promise<string>;
+getInstalledPackagePath(packageName: string, fromDir: string): string;
 ```
 
 * Usage:
 ```JavaScript
-tns.packageManager.getInstalledPackagePath("@nativescript/core", "/tmp/myProject").then(pathToPackage => {
-	console.log(pathToPackage ? `Installed at ${pathToPackage}` : "Not installed");
-});
+const pathToPackage = tns.packageManager.getInstalledPackagePath("@nativescript/core", "/tmp/myProject");
+console.log(pathToPackage ? `Installed at ${pathToPackage}` : "Not installed");
 ```
 
 ### view

lib/commands/preview.ts

@@ -37,7 +37,7 @@ export class PreviewCommand extends Command({
 			await this.installLatestPreviewCLI();
 		}
 
-		const previewCLIPath = await this.getPreviewCLIPath();
+		const previewCLIPath = this.getPreviewCLIPath();
 
 		if (!previewCLIPath) {
 			await this.failMissingPreviewCLI();
@@ -58,7 +58,7 @@ export class PreviewCommand extends Command({
 		);
 	}
 
-	private getPreviewCLIPath(): Promise<string> {
+	private getPreviewCLIPath(): string {
 		return this.$packageManager.getInstalledPackagePath(
 			PREVIEW_CLI_PACKAGE,
 			this.$projectData.projectDir,

lib/commands/test-init.ts

@@ -137,7 +137,7 @@ export class TestInitCommand extends Command({
 				path: this.$options.path,
 			});
 
-			const modulePath = await this.$packageManager.getInstalledPackagePath(
+			const modulePath = this.$packageManager.getInstalledPackagePath(
 				mod.name,
 				projectDir,
 			);

lib/commands/test.ts

@@ -106,7 +106,7 @@ async function canExecuteTestCommand(
 
 	if ($vitestExecutionService.isVitestProject($projectData)) {
 		const canStartTestRun =
-			await $vitestExecutionService.canStartTestRun($projectData);
+			$vitestExecutionService.canStartTestRun($projectData);
 		if (!canStartTestRun) {
 			$errors.fail({
 				formatStr:

lib/common/definitions/json-file-settings-service.d.ts

@@ -13,6 +13,11 @@ interface IJsonFileSettingsService {
 		settingName: string,
 		cacheOpts?: ICacheTimeoutOpts
 	): Promise<T>;
+	/**
+	 * Reads a setting without taking the settings lock. Suitable for values that
+	 * only change through explicit user commands, where a torn read is harmless.
+	 */
+	getSettingValueSync<T>(settingName: string): T;
 	saveSetting<T>(
 		key: string,
 		value: T,

lib/common/services/json-file-settings-service.ts

@@ -56,6 +56,28 @@ export class JsonFileSettingsService implements IJsonFileSettingsService {
 		);
 	}
 
+	public getSettingValueSync<T>(settingName: string): T {
+		if (!this.jsonSettingsData && this.$fs.exists(this.jsonSettingsFilePath)) {
+			try {
+				this.jsonSettingsData = parseJson(
+					this.$fs.readText(this.jsonSettingsFilePath)
+				);
+			} catch (err) {
+				this.$logger.trace(
+					`Error while trying to parse ${this.jsonSettingsFilePath}. Err is: ${err}`
+				);
+				return null;
+			}
+		}
+
+		if (this.jsonSettingsData && _.has(this.jsonSettingsData, settingName)) {
+			const data = this.jsonSettingsData[settingName];
+			return data.modifiedByCacheMechanism ? data.value : data;
+		}
+
+		return null;
+	}
+
 	public async saveSetting<T>(
 		key: string,
 		value: T,

lib/common/test/unit-tests/services/json-file-settings-service.ts

@@ -65,6 +65,37 @@ describe("jsonFileSettingsService", () => {
 		Date.now = originalDateNow;
 	});
 
+	describe("getSettingValueSync", () => {
+		it("returns the stored value without going through the lock", () => {
+			const testInjector = createTestInjector();
+			dataInFile[jsonFileSettingsPath] = { prop1: "value1" };
+			const lockService = testInjector.resolve("lockService");
+			lockService.executeActionWithLock = () => {
+				throw new Error("lock must not be used for sync reads");
+			};
+
+			const jsonFileSettingsService =
+				testInjector.resolve<IJsonFileSettingsService>(
+					"jsonFileSettingsService",
+					{ jsonFileSettingsPath }
+				);
+			assert.equal(jsonFileSettingsService.getSettingValueSync("prop1"), "value1");
+			assert.isNull(jsonFileSettingsService.getSettingValueSync("missing"));
+		});
+
+		it("returns null when the settings file does not exist", () => {
+			const testInjector = createTestInjector();
+			const fs = testInjector.resolve("fs");
+			fs.exists = () => false;
+			const jsonFileSettingsService =
+				testInjector.resolve<IJsonFileSettingsService>(
+					"jsonFileSettingsService",
+					{ jsonFileSettingsPath }
+				);
+			assert.isNull(jsonFileSettingsService.getSettingValueSync("prop1"));
+		});
+	});
+
 	describe("getSettingValue", () => {
 		it("returns correct data without cache", async () => {
 			dataInFile = { [jsonFileSettingsPath]: { prop1: 1 } };

lib/contracts/doctor-service.ts

@@ -34,7 +34,5 @@ export abstract class DoctorService {
 	}): Promise<boolean>;
 
 	/** Checks and notifies users of deprecated short imports in their app. */
-	abstract checkForDeprecatedShortImportsInAppDir(
-		projectDir: string,
-	): Promise<void>;
+	abstract checkForDeprecatedShortImportsInAppDir(projectDir: string): void;
 }

lib/contracts/package-manager.ts

@@ -103,12 +103,12 @@ export abstract class PackageManager {
 	 * Locates a package the way the package manager laid it out on disk.
 	 * @param  {string} packageName The name of the package.
 	 * @param  {string} fromDir     The directory whose dependencies are searched, usually the project directory.
-	 * @return {Promise<string>} The absolute path of the package directory, or null when it is not installed.
+	 * @return {string} The absolute path of the package directory, or null when it is not installed.
 	 */
 	abstract getInstalledPackagePath(
 		packageName: string,
 		fromDir: string,
-	): Promise<string>;
+	): string;
 
 	/**
 	 * Gets the name of the package manager used for the current process.

lib/controllers/prepare-controller.ts

@@ -494,11 +494,10 @@ export class PrepareController
 				SCOPED_ANDROID_RUNTIME_NAME;
 		}
 		// try reading from installed runtime first before reading from the npm registry...
-		const installedRuntimePath =
-			await this.$packageManager.getInstalledPackagePath(
-				runtimePackageName,
-				projectData.projectDir,
-			);
+		const installedRuntimePath = this.$packageManager.getInstalledPackagePath(
+			runtimePackageName,
+			projectData.projectDir,
+		);
 
 		if (installedRuntimePath) {
 			installedRuntimePackageJSON = this.$fs.readJson(