fix: fix optional looking up (#32)

package.json

@@ -1,5 +1,5 @@
 {
-  "$schema": "https://raw.githubusercontent.com/wzhudev/squirrel/master/src/schema/package.schema.json",
+  "schema": "https://raw.githubusercontent.com/wzhudev/squirrel/master/src/schema/package.schema.json",
   "name": "@wendellhu/redi",
   "version": "0.16.1",
   "description": "A dependency library for TypeScript and JavaScript, along with a binding for React.",

pnpm-workspace.yaml

@@ -1,3 +1,3 @@
 packages:
     - ./
-    - doc/
+    - docs/

src/dependencyQuantity.ts

@@ -8,16 +8,24 @@ import { Ctor, prettyPrintIdentifier } from './dependencyItem'
 import { RediError } from './error'
 import { Quantity } from './types'
 
-class QuantityCheckError extends RediError {
+export class QuantityCheckError extends RediError {
   constructor(
     id: DependencyIdentifier<any>,
-    quantity: Quantity,
-    actual: number
+    public readonly quantity: Quantity,
+    public readonly actual: number
   ) {
-    const msg = `Expect "${quantity}" dependency items for id "${prettyPrintIdentifier(
+    let msg = `Expect "${quantity}" dependency items for id "${prettyPrintIdentifier(
       id
     )}" but get ${actual}.`
 
+    if (actual == 0) {
+      msg += ' Did you forget to register it?'
+    }
+
+    if (actual > 1) {
+      msg += ' You register it more than once.'
+    }
+
     super(msg)
   }
 }

src/injector.ts

@@ -31,6 +31,7 @@ import {
   isExistingDependencyItem,
   ExistingDependencyItem,
 } from './dependencyItem'
+import { checkQuantity, QuantityCheckError } from './dependencyQuantity'
 import { RediError } from './error'
 import { IdleValue } from './idleValue'
 import { LookUp, Quantity } from './types'
@@ -525,7 +526,7 @@ export class Injector {
         )
         resolvedArgs.push(thing)
       } catch (error: unknown) {
-        if (error instanceof DependencyNotFoundError) {
+        if (error instanceof DependencyNotFoundError || (error instanceof QuantityCheckError && error.actual === 0)) {
           throw new DependencyNotFoundForModuleError(
             ctor,
             dep.identifier,
@@ -586,7 +587,7 @@ export class Injector {
         )
         resolvedArgs.push(thing)
       } catch (error: unknown) {
-        if (error instanceof DependencyNotFoundError) {
+        if (error instanceof DependencyNotFoundError || (error instanceof QuantityCheckError && error.actual === 0)) {
           throw new DependencyNotFoundForModuleError(
             id,
             dep.identifier,
@@ -677,14 +678,25 @@ export class Injector {
       if (this.parent) {
         return this.parent.getValue(id, quantity)
       } else {
-        return NotInstantiatedSymbol
+        // If the parent injector is missing, we should check quantity with 0 values.
+        checkQuantity(id, quantity, 0);
+
+        if (quantity === Quantity.MANY) {
+          return []
+        } else {
+          return null
+        }
       }
     }
 
     if (lookUp === LookUp.SKIP_SELF) {
       return onParent()
     }
 
+    if (id === Injector) {
+      return this as unknown as T;
+    }
+
     if (lookUp === LookUp.SELF) {
       return onSelf()
     }
@@ -740,10 +752,6 @@ export class Injector {
       return onParent()
     }
 
-    if ((id as any as Ctor<Injector>) === Injector) {
-      return this as any as T
-    }
-
     if (this.dependencyCollection.has(id)) {
       return onSelf()
     }

test/core.spec.ts

@@ -13,6 +13,8 @@ import {
   setDependencies,
   SkipSelf,
   WithNew,
+  Quantity,
+  LookUp,
 } from '@wendellhu/redi'
 
 import { TEST_ONLY_clearKnownIdentifiers } from '../src/decorators'
@@ -705,6 +707,7 @@ describe('core', () => {
         const j = new Injector([[aI, { useValue: a }]])
 
         // totally verbose for real use case, but to show this works
+        expect(j.get(Injector)).toBe(j)
         expect(j.get(Injector).get(aI).key).toBe('a')
       })
     })
@@ -964,7 +967,7 @@ describe('core', () => {
 
       expectToThrow(
         () => j.get(A),
-        `[redi]: Cannot find "A" registered by any injector.`
+        `[redi]: Expect "required" dependency items for id "A" but get 0. Did you forget to register it?`
       )
     })
   })
@@ -1245,6 +1248,17 @@ describe('core', () => {
     })
   })
 
+  describe('Lookup', () => {
+    it('should support optional lookup even if parent does not exist', () => {
+      class A { }
+
+      const parentInjector = new Injector()
+      const childInjector = parentInjector.createChild([[A]])
+
+      expect(childInjector.get(A, Quantity.OPTIONAL, LookUp.SKIP_SELF)).toBeNull()
+    });
+  })
+
   it('should throw error when identifier has been declared before', () => {
     createIdentifier('a')