feat: allow autoloading of non-default exports (#115)

Add support for auto-loading named exports that expose an object on the `RESOLVER` symbol property.

Author: whefter

README.md

@@ -451,6 +451,29 @@ boring. You can automate this by using `loadModules`.
 > * `module.exports = ...`
 > * `module.exports.default = ...`
 > * `export default ...`
+> 
+> To load a non-default export, set the `[RESOLVER]` property on it:
+> 
+> ```js
+> const { RESOLVER } = require('awilix');
+> export class ServiceClass {
+> }
+> ServiceClass[RESOLVER] = {}
+> ```
+>
+> Or even more concise using TypeScript:
+> ```typescript
+> // TypeScript
+> import { RESOLVER } from 'awilix'
+> export class ServiceClass {
+>   static [RESOLVER] = {}
+> }
+> ```
+
+Note that **multiple** services can be registered per file, i.e. it is
+possible to have a file with a default export and named exports and for
+all of them to be loaded. The named exports do require the `RESOLVER`
+token to be recognized.
 
 Imagine this app structure:
 

src/__tests__/load-modules.test.ts

@@ -37,6 +37,133 @@ describe('loadModules', function() {
     expect(container.resolve('someClass')).toBeInstanceOf(SomeClass)
   })
 
+  it('registers non-default export modules containing RESOLVER token with the container', function() {
+    const container = createContainer()
+
+    class SomeNonDefaultClass {
+      static [RESOLVER] = {}
+    }
+
+    const modules: any = {
+      'someIgnoredName.js': { SomeNonDefaultClass }
+    }
+    const moduleLookupResult = lookupResultFor(modules)
+    const deps = {
+      container,
+      listModules: jest.fn(() => moduleLookupResult),
+      require: jest.fn(path => modules[path])
+    }
+
+    const result = loadModules(deps, 'anything')
+    expect(result).toEqual({ loadedModules: moduleLookupResult })
+    expect(Object.keys(container.registrations).length).toBe(1)
+    // Note the capital first letter because the export key name is used instead of the filename
+    expect(container.resolve('SomeNonDefaultClass')).toBeInstanceOf(
+      SomeNonDefaultClass
+    )
+  })
+
+  it('does not register non-default modules without a RESOLVER token', function() {
+    const container = createContainer()
+
+    class SomeClass {}
+
+    const modules: any = {
+      'nopeClass.js': { SomeClass }
+    }
+    const moduleLookupResult = lookupResultFor(modules)
+    const deps = {
+      container,
+      listModules: jest.fn(() => moduleLookupResult),
+      require: jest.fn(path => modules[path])
+    }
+
+    const result = loadModules(deps, 'anything')
+    expect(result).toEqual({ loadedModules: moduleLookupResult })
+    expect(Object.keys(container.registrations).length).toBe(0)
+  })
+
+  it('registers multiple loaded modules from one file with the container', function() {
+    const container = createContainer()
+
+    class SomeClass {}
+    class SomeNonDefaultClass {
+      static [RESOLVER] = {}
+    }
+    class SomeNamedNonDefaultClass {
+      static [RESOLVER] = {
+        name: 'nameOverride'
+      }
+    }
+
+    const modules: any = {
+      'mixedFile.js': {
+        default: SomeClass,
+        nonDefault: SomeNonDefaultClass,
+        namedNonDefault: SomeNamedNonDefaultClass
+      }
+    }
+    const moduleLookupResult = lookupResultFor(modules)
+    const deps = {
+      container,
+      listModules: jest.fn(() => moduleLookupResult),
+      require: jest.fn(path => modules[path])
+    }
+
+    const result = loadModules(deps, 'anything')
+    expect(result).toEqual({ loadedModules: moduleLookupResult })
+    expect(Object.keys(container.registrations).length).toBe(3)
+    expect(container.resolve('mixedFile')).toBeInstanceOf(SomeClass)
+    expect(container.resolve('nonDefault')).toBeInstanceOf(SomeNonDefaultClass)
+    expect(container.resolve('nameOverride')).toBeInstanceOf(
+      SomeNamedNonDefaultClass
+    )
+  })
+
+  it('registers only the last module with a certain name with the container', function() {
+    const container = createContainer()
+
+    class SomeClass {}
+    class SomeNonDefaultClass {
+      static [RESOLVER] = {}
+    }
+    class SomeNamedNonDefaultClass {
+      static [RESOLVER] = {
+        name: 'nameOverride'
+      }
+    }
+
+    const modules: any = {
+      'mixedFileOne.js': {
+        default: SomeClass,
+        nameOverride: SomeNonDefaultClass,
+        // this will override the above named export with its specified name
+        namedNonDefault: SomeNamedNonDefaultClass
+      },
+      'mixedFileTwo.js': {
+        // this will override the default export from mixedFileOne
+        mixedFileOne: SomeNonDefaultClass
+      }
+    }
+
+    const moduleLookupResult = lookupResultFor(modules)
+    const deps = {
+      container,
+      listModules: jest.fn(() => moduleLookupResult),
+      require: jest.fn(path => modules[path])
+    }
+
+    const result = loadModules(deps, 'anything')
+    expect(result).toEqual({ loadedModules: moduleLookupResult })
+    expect(Object.keys(container.registrations).length).toBe(2)
+    expect(container.resolve('mixedFileOne')).toBeInstanceOf(
+      SomeNonDefaultClass
+    )
+    expect(container.resolve('nameOverride')).toBeInstanceOf(
+      SomeNamedNonDefaultClass
+    )
+  })
+
   it('uses built-in formatter when given a formatName as a string', function() {
     const container = createContainer()
     const modules: any = {

src/load-modules.ts

@@ -90,35 +90,68 @@ export function loadModules(
   const modules = dependencies.listModules(globPatterns, opts)
 
   const result = modules.map(m => {
+    const items: Array<{
+      name: string
+      path: string
+      opts: object
+      value: unknown
+    }> = []
+
     const loaded = dependencies.require(m.path)
 
     // Meh, it happens.
     if (!loaded) {
-      return undefined
+      return items
+    }
+
+    if (isFunction(loaded)) {
+      // for module.exports = ...
+      items.push({
+        name: m.name,
+        path: m.path,
+        value: loaded,
+        opts: m.opts
+      })
+
+      return items
+    }
+
+    if (loaded.default && isFunction(loaded.default)) {
+      // ES6 default export
+      items.push({
+        name: m.name,
+        path: m.path,
+        value: loaded.default,
+        opts: m.opts
+      })
     }
 
-    if (!isFunction(loaded)) {
-      if (loaded.default && isFunction(loaded.default)) {
-        // ES6 default export
-        return {
-          name: m.name,
+    // loop through non-default exports, but require the RESOLVER property set for
+    // it to be a valid service module export.
+    for (const key of Object.keys(loaded)) {
+      if (key === 'default') {
+        // default case handled separately due to its different name (file name)
+        continue
+      }
+
+      if (isFunction(loaded[key]) && RESOLVER in loaded[key]) {
+        items.push({
+          name: key,
           path: m.path,
-          value: loaded.default,
+          value: loaded[key],
           opts: m.opts
-        }
+        })
       }
-
-      return undefined
     }
 
-    return {
-      name: m.name,
-      path: m.path,
-      value: loaded,
-      opts: m.opts
-    }
+    return items
   })
-  result.filter(x => x).forEach(registerDescriptor.bind(null, container, opts))
+
+  result
+    .reduce((acc, cur) => acc.concat(cur), [])
+    .filter(x => x)
+    .forEach(registerDescriptor.bind(null, container, opts))
+
   return {
     loadedModules: modules
   }