Allow using an alternate fs for lookup of sources

.vscode/launch.json

@@ -0,0 +1,22 @@
+{
+    "version": "0.2.0",
+    "configurations": [        
+        {
+            "name": "Run mocha",
+            "type": "node",
+            "request": "launch",
+            "program": "${workspaceRoot}/node_modules/mocha/bin/_mocha",
+            "stopOnEntry": false,
+            "args": [
+                "test/test.js",
+                "--no-timeouts"
+            ],
+            "sourceMaps": true,
+            "cwd": "${workspaceRoot}",
+            "runtimeExecutable": null,
+            "env": {
+                "NODE_ENV": "testing"
+            }
+        }
+    ]
+}

index.js

@@ -45,6 +45,7 @@ const defaultLookups = {
  * @param {String} [options.webpackConfig] Path to the webpack config
  * @param {Object} [options.ast] A preparsed AST for the file identified by filename.
  * @param {Object} [options.tsconfig] Path to a typescript config file
+ * @param {Object} [options.fileSystem] An alternative filesystem / fs implementation to use for locating files.
  */
 module.exports = function cabinet(options) {
   const {
@@ -173,7 +174,7 @@ function jsLookup({dependency, filename, directory, config, webpackConfig, confi
   }
 }
 
-function tsLookup({dependency, filename, tsConfig}) {
+function tsLookup({dependency, filename, tsConfig, fileSystem}) {
   debug('performing a typescript lookup');
 
   const defaultTsConfig = {
@@ -186,15 +187,16 @@ function tsLookup({dependency, filename, tsConfig}) {
 
   debug('given typescript config: ', tsConfig);
 
+  var fileSystem = fileSystem || fs;
+
   if (!tsConfig) {
     tsConfig = defaultTsConfig;
     debug('no tsconfig given, defaulting');
 
   } else if (typeof tsConfig === 'string') {
     debug('string tsconfig given, parsing');
-
     try {
-      tsConfig = JSON.parse(fs.readFileSync(tsConfig, 'utf8'));
+      tsConfig = JSON.parse(fileSystem.readFileSync(tsConfig, 'utf8'));
       debug('successfully parsed tsconfig');
     } catch (e) {
       debug('could not parse tsconfig');
@@ -212,7 +214,17 @@ function tsLookup({dependency, filename, tsConfig}) {
     options.module = ts.ModuleKind.AMD;
   }
 
-  const host = ts.createCompilerHost({});
+  var host = ts.createCompilerHost({});
+
+  // Override host methods, to support finding files in provided fs.
+  const isDirectory = dirPath => fileSystem.lstatSync(dirPath).isDirectory();
+  const getDirectories = dirPath => fileSystem.readdirSync(dirPath).map(name => path.join(dirPath, name)).filter(isDirectory);
+  const pathExists = filePath => fileSystem.existsSync(filePath);
+
+  host.getDirectories = getDirectories;
+  host.fileExists = pathExists;
+  host.directoryExists = pathExists;
+
   debug('with options: ', options);
   const resolvedModule = ts.resolveModuleName(dependency, filename, options, host).resolvedModule;
   debug('ts resolved module: ', resolvedModule);

package.json

@@ -41,7 +41,9 @@
     "mocha": "^5.0.0",
     "mock-fs": "^4.4.2",
     "rewire": "^4.0.1",
-    "sinon": "^4.1.6"
+    "sinon": "^4.1.6",
+    "unionfs": "^3.0.2",
+    "memfs": "^2.14.1"
   },
   "dependencies": {
     "app-module-path": "^2.2.0",

test/mockedJSFiles.js

@@ -12,7 +12,7 @@ module.exports = {
     'ts': {
       'index.ts': 'import foo from "./foo";',
       'foo.ts': 'export default 1;',
-      '.tsconfig': '{ "version": "1.0.0", "compilerOptions": { "module": "commonjs" } }'
+      '.tsconfig': '{ "version": "1.0.0", "compilerOptions": { "module": "commonjs" } }',
     },
     'amd': {
       'foo.js': 'define(["./bar"], function(bar){ return bar; });',

test/test.js

@@ -369,6 +369,31 @@ describe('filing-cabinet', function() {
         );
       });
 
+      it('resolves an import using an alternative fs', function() {
+        mock.restore();
+        const volumeDir = 'app';
+        const filename = volumeDir + '/index.ts';
+
+        const unionfs = require('unionfs');
+        const memfs = require('memfs');
+
+        // mount files specified by "mockedFiles.js.ts" to "app" base directory.
+        var vol = memfs.Volume.fromJSON(mockedFiles.js.ts, `${volumeDir}`);
+        var ufs = unionfs.ufs.use(vol);
+
+        const result = cabinet({
+          partial: './foo',
+          filename,
+          directory,
+          fileSystem: ufs
+        });
+        //directory
+        assert.equal(
+          result,
+          path.join(path.resolve('app'), 'foo.ts')
+        );
+      });
+
       describe('when a partial does not exist', function() {
         it('returns an empty result', function() {
           const filename = directory + '/index.ts';
@@ -390,7 +415,9 @@ describe('filing-cabinet', function() {
               ModuleKind: {
                 AMD: 'amd'
               },
-              createCompilerHost: sinon.stub(),
+              createCompilerHost: sinon.stub().returns({
+                getDirectories: null
+              }),
               resolveModuleName: sinon.stub().returns({
                 resolvedModule: ''
               }),
@@ -424,7 +451,9 @@ describe('filing-cabinet', function() {
               ModuleKind: {
                 AMD: 'amd'
               },
-              createCompilerHost: sinon.stub(),
+              createCompilerHost: sinon.stub().returns({
+                getDirectories: null
+              }),
               resolveModuleName: sinon.stub().returns({
                 resolvedModule: ''
               }),
@@ -456,7 +485,9 @@ describe('filing-cabinet', function() {
             ModuleKind: {
               AMD: 'amd'
             },
-            createCompilerHost: sinon.stub(),
+            createCompilerHost: sinon.stub().returns({
+              getDirectories: null
+            }),
             resolveModuleName: sinon.stub().returns({
               resolvedModule: ''
             }),