From 5b8c0590eb2305381a6eff536f2c669afaa9776d Mon Sep 17 00:00:00 2001
From: Jack Ellis <jack.m.ellis@hotmail.co.uk>
Date: Wed, 31 Jul 2024 09:57:50 +0100
Subject: [PATCH] feat: option to specify a fallback resolve value

---
 README.md                              |  8 +++++
 src/resolver/__tests__/default.test.ts | 44 ++++++++++++++++++++++++++
 src/resolver/utils.ts                  | 11 ++++++-
 src/types/JpexInstance.ts              |  1 +
 4 files changed, 63 insertions(+), 1 deletion(-)
 create mode 100644 src/resolver/__tests__/default.test.ts

diff --git a/README.md b/README.md
index 93f955e..1968d6a 100644
--- a/README.md
+++ b/README.md
@@ -302,6 +302,14 @@ boolean;
 
 When `true` if the dependency cannot be found or resolved, it will just return `undefined` rather than throwing an error.
 
+### default
+
+```ts
+any;
+```
+
+Provide a fallback value if the dependency cannot be found.
+
 #### jpex.resolveAsync
 
 ```ts
diff --git a/src/resolver/__tests__/default.test.ts b/src/resolver/__tests__/default.test.ts
new file mode 100644
index 0000000..8d17ed4
--- /dev/null
+++ b/src/resolver/__tests__/default.test.ts
@@ -0,0 +1,44 @@
+import base from '../..';
+
+const setup = () => {
+  const jpex = base.extend();
+
+  return {
+    jpex,
+  };
+};
+
+test('if factory exists, it should be resolved', () => {
+  const { jpex } = setup();
+  type Foo = string;
+  jpex.constant<Foo>('foo');
+
+  const result = jpex.resolve<Foo>({ default: 'bar' });
+
+  expect(result).toBe('foo');
+});
+
+test('if factory does not exist, it should return the default', () => {
+  const { jpex } = setup();
+  type Foo = string;
+
+  const result = jpex.resolve<Foo>({ default: 'bar' });
+
+  expect(result).toBe('bar');
+});
+
+test('if factory does not exist and default not provided, it should throw an error', () => {
+  const { jpex } = setup();
+  type Foo = string;
+
+  expect(() => jpex.resolve<Foo>()).toThrow();
+});
+
+test('if factory does not exist and default is undefined, it should return undefined', () => {
+  const { jpex } = setup();
+  type Foo = string;
+
+  const result = jpex.resolve<Foo>({ default: undefined });
+
+  expect(result).toBe(undefined);
+});
diff --git a/src/resolver/utils.ts b/src/resolver/utils.ts
index f5967ce..c4ef348 100644
--- a/src/resolver/utils.ts
+++ b/src/resolver/utils.ts
@@ -95,7 +95,7 @@ export const getFactory = (
   jpex: JpexInstance,
   name: string,
   opts: ResolveOpts = {},
-) => {
+): Factory | undefined => {
   validateName(name);
   const fns = [
     getFromResolved,
@@ -115,6 +115,15 @@ export const getFactory = (
     return;
   }
 
+  if ('default' in opts) {
+    return {
+      fn: () => opts.default,
+      lifecycle: jpex.$$config.lifecycle,
+      resolved: true,
+      value: opts.default,
+    };
+  }
+
   throw new Error(`Unable to find required dependency [${name}]`);
 };
 
diff --git a/src/types/JpexInstance.ts b/src/types/JpexInstance.ts
index ee94563..ce89a47 100644
--- a/src/types/JpexInstance.ts
+++ b/src/types/JpexInstance.ts
@@ -30,6 +30,7 @@ export interface ResolveOpts {
   optional?: boolean;
   with?: NamedParameters;
   async?: boolean;
+  default?: any;
 }
 
 export interface JpexInstance {