[INTERNAL] ProjectGraph: Refactor API

Refactor some methods based on current usage.

* Internal: Use Maps and Sets instead of objects and arrays
* Rename several methods
* Traversal callbacks: Provide array of dependency names instead of a
  getDependency() function. Most consumers only need the names.
  Corresponding projects can be easily retrieved via getProject()
* Traversal callbacks: Callback can be synchronous. Before, we required
  a promise to be returned. Many consumers actually do not need to
  perform async tasks
* Add a method for retrieving the names of all projects in the graph.
  This is a common requirement
* Add a method for retrieving the number of projects in the graph.
  This is also a common requirement
* join: Fix taking over optional dependencies and correspoinding flag
* addProject: Remove option to ignore duplicates. This was never used

lib/build/ProjectBuilder.js

@@ -162,7 +162,7 @@ class ProjectBuilder {
 		});
 
 		// Count total number of projects to build based on input
-		const requestedProjects = this._graph.getAllProjects().map((p) => p.getName()).filter(function(projectName) {
+		const requestedProjects = this._graph.getProjectNames().filter(function(projectName) {
 			return filterProject(projectName);
 		});
 
@@ -264,18 +264,16 @@ class ProjectBuilder {
 	}
 
 	async _createRequiredBuildContexts(requestedProjects) {
-		const allProjects = this._graph.getAllProjects();
-		const requiredProjects = new Set(allProjects.filter((project) => {
-			return requestedProjects.includes(project.getName());
+		const requiredProjects = new Set(this._graph.getProjectNames().filter((projectName) => {
+			return requestedProjects.includes(projectName);
 		}));
 
 		const projectBuildContexts = new Map();
 
-		for (const project of requiredProjects) {
-			const projectName = project.getName();
+		for (const projectName of requiredProjects) {
 			log.verbose(`Creating build context for project ${projectName}...`);
 			const projectBuildContext = this._buildContext.createProjectContext({
-				project,
+				project: this._graph.getProject(projectName),
 				log
 			});
 
@@ -299,8 +297,7 @@ class ProjectBuilder {
 						return;
 					}
 					// Add dependency to list of projects to build
-					const depProject = this._graph.getProject(depName);
-					requiredProjects.add(depProject);
+					requiredProjects.add(depName);
 				});
 			}
 		}
@@ -322,7 +319,7 @@ class ProjectBuilder {
 		);
 
 		if (includedDependencies.length) {
-			if (includedDependencies.length === this._graph.getAllProjects().length - 1) {
+			if (includedDependencies.length === this._graph.getSize() - 1) {
 				log.info(`  Including all dependencies`);
 			} else {
 				log.info(`  Requested dependencies:`);

lib/build/TaskRunner.js

@@ -450,7 +450,7 @@ class TaskRunner {
 		// Add transitive dependencies to set of required dependencies
 		const requiredDependencies = new Set(requiredDirectDependencies);
 		for (const projectName of requiredDirectDependencies) {
-			this._graph.getAllDependencies(projectName).forEach((depName) => {
+			this._graph.getTransitiveDependencies(projectName).forEach((depName) => {
 				requiredDependencies.add(depName);
 			});
 		}

lib/build/helpers/composeProjectList.js

@@ -13,14 +13,13 @@ async function getFlattenedDependencyTree(graph) {
 	const dependencyMap = Object.create(null);
 	const rootName = graph.getRoot().getName();
 
-	await graph.traverseDepthFirst(({project, getDependencies}) => {
+	await graph.traverseDepthFirst(({project, dependencies}) => {
 		if (project.getName() === rootName) {
 			// Skip root project
 			return;
 		}
 		const projectDeps = [];
-		getDependencies().forEach((dep) => {
-			const depName = dep.getName();
+		dependencies.forEach((depName) => {
 			projectDeps.push(depName);
 			if (dependencyMap[depName]) {
 				projectDeps.push(...dependencyMap[depName]);