feat: Rename useVirtualFileSystem to useInMemoryFileSystem

BREAKING CHANGE: `ProjectOptions#useVirtualFileSystem` is now `useInMemoryFileSystem`. This is a more accurate name.

.travis.yml

@@ -6,7 +6,7 @@ before_script:
     - travis_wait yarn build
     - lerna run ensure-no-project-compile-errors
 script:
-    - travis_wait lerna run test:ci # running coveralls might take a bit of time
+    - lerna run test:ci
     - lerna run test:ts-versions
 after_script:
     - lerna run code-verification

docs/setup/ast-viewers.md

@@ -18,6 +18,7 @@ Features:
 * View the type and symbol of the selected node.
 * Toggle the tree between `node.forEachChild(...)` and `node.getChildren()`.
 * Change compiler API versions.
+* Use some compiler objects in the browser console.
 
 [![TypeScript AST Viewer](images/ts-ast-viewer.png)](http://ts-ast-viewer.com)
 

docs/setup/file-system.md

@@ -4,8 +4,7 @@ title: File System
 
 ## File System
 
-By default, the library will use the local file system based on the current working directory. In most scenarios, you won't have to bother with what's outlined here, but it may
-by useful in some scenarios (for example, using a virtual file system is useful for mocking the file system for testing purposes).
+By default, the library will use the local file system based on the current working directory. In most scenarios, you won't have to bother with what's outlined here, but it may be useful in some scenarios (for example, using an in-memory file system is useful for mocking the file system for testing purposes).
 
 ### Current File System Object
 
@@ -19,35 +18,34 @@ const fs = project.getFileSystem(); // returns: FileSystemHost
 This file system object can be used to interact with the current file system. The methods available on it are very obvious and not worth explaining
 here (ex. `writeFile(filePath: string, fileText: string): Promise<void>`, `readFile(filePath: string): Promise<string>`, `readFileSync(filePath: string): string`, etc..).
 
-### Virtual File System
+### In-Memory File System
 
-If you want to use a virtual file system that is stored in memory, specify that when creating an `Ast` object:
+If you want to use a file system that is stored in memory, specify that when creating a `Project` instance:
 
 ```ts
 import { Project } from "ts-morph";
 
-const project = new Project({ useVirtualFileSystem: true });
+const project = new Project({ useInMemoryFileSystem: true });
 const fs = project.getFileSystem();
 
-// note that it's ok to use synchronous commands when using a virtual file system
 const sourceFile = project.createSourceFile("file.ts", "console.log(5);");
 sourceFile.saveSync();
-fs.readFileSync("file.ts"); // returns: "console.log(5);"
+console.log(fs.readFileSync("file.ts")); // outputs: "console.log(5);"
 ```
 
 The current working directory on this file system will be `/`.
 
 #### `lib.d.ts` files
 
-Since ts-morph 6.0, the virtual file system will have the [`lib.d.ts` files](https://github.com/Microsoft/TypeScript/tree/master/lib) loaded into the `/node_modules/typescript/lib` folder by default.
+Since ts-morph 6.0, the in memory file system will have the [`lib.d.ts` files](https://github.com/Microsoft/TypeScript/tree/master/lib) loaded into the `/node_modules/typescript/lib` folder by default.
 
 If you want the old behaviour, you can specify to skip loading them by providing a `skipLoadingLibFiles` option:
 
 ```ts ignore-error: 1109
 import { Project, FileSystemHost } from "ts-morph";
 
 const project = new Project({
-    useVirtualFileSystem: true,
+    inMemoryFileSystem: true,
     skipLoadingLibFiles: true
 });
 
@@ -58,7 +56,7 @@ When using a non-default file system, the library will search for these files in
 
 ### Custom File System
 
-It's possible to use your own custom file system by implementing the `FileSystemHost` interface then passing in an instance of this when creating a new `Ast` object:
+It's possible to use your own custom file system by implementing the `FileSystemHost` interface then passing in an instance of this when creating a new `Project` instance:
 
 ```ts ignore-error: 2420, 2345
 import { Project, FileSystemHost } from "ts-morph";

packages/bootstrap/lib/ts-morph-bootstrap.d.ts

@@ -122,19 +122,19 @@ export interface ProjectOptions {
     /** Skip resolving file dependencies when providing a ts config file path and adding the files from tsconfig. */
     skipFileDependencyResolution?: boolean;
     /** Whether to use an in-memory file system. */
-    useVirtualFileSystem?: boolean;
+    useInMemoryFileSystem?: boolean;
+    /** Skip loading the lib files when using an in-memory file system. @default false */
+    skipLoadingLibFiles?: boolean;
     /**
      * Optional file system host. Useful for mocking access to the file system.
-     * @remarks Consider using `useVirtualFileSystem` instead.
+     * @remarks Consider using `inMemoryFileSystem` instead.
      */
     fileSystem?: FileSystemHost;
     /** Creates a resolution host for specifying custom module and/or type reference directive resolution. */
     resolutionHost?: ResolutionHostFactory;
 }
 
-/**
- * Project that holds source files.
- */
+/** Project that holds source files. */
 export declare class Project {
     /**
      * Initializes a new instance.

packages/bootstrap/readme.md

@@ -51,7 +51,7 @@ const project = new Project({ tsConfigFilePath: "tsconfig.json" });
 const project = new Project();
 
 // in memory file system
-const project2 = new Project({ useVirtualFileSystem: true });
+const project2 = new Project({ inMemoryFileSystem: true });
 
 // custom file system
 const fileSystem: FileSystemHost = { ...etc... };
@@ -182,7 +182,7 @@ project.removeSourceFile(sourceFile);
 ```ts
 import { Project, ts } from "@ts-morph/bootstrap";
 
-const project = new Project({ useVirtualFileSystem: true });
+const project = new Project({ inMemoryFileSystem: true });
 project.createSourceFile("test.ts", "const t: string = 5;");
 
 const program = project.createProgram();

packages/bootstrap/src/Project.ts

@@ -13,19 +13,19 @@ export interface ProjectOptions {
     /** Skip resolving file dependencies when providing a ts config file path and adding the files from tsconfig. */
     skipFileDependencyResolution?: boolean;
     /** Whether to use an in-memory file system. */
-    useVirtualFileSystem?: boolean;
+    useInMemoryFileSystem?: boolean;
+    /** Skip loading the lib files when using an in-memory file system. @default false */
+    skipLoadingLibFiles?: boolean;
     /**
      * Optional file system host. Useful for mocking access to the file system.
-     * @remarks Consider using `useVirtualFileSystem` instead.
+     * @remarks Consider using `inMemoryFileSystem` instead.
      */
     fileSystem?: FileSystemHost;
     /** Creates a resolution host for specifying custom module and/or type reference directive resolution. */
     resolutionHost?: ResolutionHostFactory;
 }
 
-/**
- * Project that holds source files.
- */
+/** Project that holds source files. */
 export class Project {
     /** @internal */
     private readonly _sourceFileCache: SourceFileCache;
@@ -41,6 +41,8 @@ export class Project {
      * @param options - Optional options.
      */
     constructor(options: ProjectOptions = {}) {
+        verifyOptions();
+
         this.fileSystem = getFileSystem();
         this._fileSystemWrapper = new TransactionalFileSystem(this.fileSystem);
 
@@ -86,13 +88,20 @@ export class Project {
                 this.resolveSourceFileDependencies();
         }
 
-        function getFileSystem(): FileSystemHost {
-            // setup file system
-            if (options.fileSystem != null && options.useVirtualFileSystem)
-                throw new errors.InvalidOperationError("Cannot provide a file system when specifying to use a virtual file system.");
-            else if (options.useVirtualFileSystem)
-                return new InMemoryFileSystemHost();
-            return options.fileSystem || new RealFileSystemHost();
+        function verifyOptions() {
+            if (options.fileSystem != null && options.useInMemoryFileSystem)
+                throw new errors.InvalidOperationError("Cannot provide a file system when specifying to use an in-memory file system.");
+            if (options.skipLoadingLibFiles && !options.useInMemoryFileSystem) {
+                throw new errors.InvalidOperationError(
+                    `The ${nameof(options.skipLoadingLibFiles)} option can only be true when ${nameof(options.useInMemoryFileSystem)} is true.`
+                );
+            }
+        }
+
+        function getFileSystem() {
+            if (options.useInMemoryFileSystem)
+                return new InMemoryFileSystemHost({ skipLoadingLibFiles: options.skipLoadingLibFiles });
+            return options.fileSystem ?? new RealFileSystemHost();
         }
 
         function getCompilerOptions(): ts.CompilerOptions {