Tighten up KeyGenerators API (fixes #3)

src/keyGenerators.ts

@@ -5,13 +5,24 @@ import {GeneratorFunc} from './types';
  * A selection of predefined {@link GeneratorFunc} functions to choose from.
  */
 export class KeyGenerators {
+  /**
+   * Validates and normalizes a key candidate.  Keys must be strings or convertible to strings (number, boolean, etc).
+   *
+   * @param {unknown} key - The key candidate.
+   * @return string
+   */
+  private static normalizeKey = (key: unknown) =>
+    key === undefined || typeof key === 'object' ? '' : String(key);
+
   /**
    * Use the existing key.  Useful when adding elements to an array that already has keys.
    * If used, will usually be the first generator provided.
    *
    * @return GeneratorFunc
    */
-  static existingKey = (): GeneratorFunc => (obj: any) => obj.key || undefined; // eslint-disable-line @typescript-eslint/no-explicit-any
+  static existingKey = (): GeneratorFunc => (
+    obj: any // eslint-disable-line @typescript-eslint/no-explicit-any
+  ) => KeyGenerators.normalizeKey(obj.key);
 
   /**
    * A property extractor, allowing the objects to be walked until the leaf node is extracted.
@@ -26,7 +37,7 @@ export class KeyGenerators {
 
     const target = path.reduce((prev, prop) => prev[prop], obj);
 
-    return !target || typeof target === 'object' ? '' : String(target);
+    return KeyGenerators.normalizeKey(target);
   };
 
   /**

test/keyGenerators.test.ts

@@ -31,18 +31,32 @@ describe('existingKey', () => {
     expect(generator(elementWithKey)).toBe(existingKey);
   });
 
-  it('is undefined for blank key', () => {
+  it('is blank for blank key', () => {
     const elementWithKey = {...testElement};
     elementWithKey.key = '';
 
-    expect(generator(elementWithKey)).toBeUndefined();
+    expect(generator(elementWithKey)).toBe('');
   });
 
-  it('is undefined for non-existing key', () => {
+  it('is blank for non-existing key', () => {
     const elementWithKey = {...testElement};
     elementWithKey.key = undefined;
 
-    expect(generator(elementWithKey)).toBeUndefined();
+    expect(generator(elementWithKey)).toBe('');
+  });
+
+  it('works with the number 0', () => {
+    const elementWithKey = {...testElement} as any;
+    elementWithKey.key = 0;
+
+    expect(generator(elementWithKey)).toBe(String(elementWithKey.key));
+  });
+
+  it('works with the boolean false', () => {
+    const elementWithKey = {...testElement} as any;
+    elementWithKey.key = false;
+
+    expect(generator(elementWithKey)).toBe(String(elementWithKey.key));
   });
 });
 
@@ -74,6 +88,24 @@ describe('fromPropertyPath', () => {
       expect(generator(elementWithProp)).toBe(String(elementWithProp.id));
     });
 
+    it('works with the number 0', () => {
+      const generator = KeyGenerators.fromPropertyPath("id");
+
+      const elementWithProp = {...testElement};
+      elementWithProp.id = 0;
+
+      expect(generator(elementWithProp)).toBe(String(elementWithProp.id));
+    });
+
+    it('works with the boolean false', () => {
+      const generator = KeyGenerators.fromPropertyPath("id");
+
+      const elementWithProp = {...testElement};
+      elementWithProp.id = false;
+
+      expect(generator(elementWithProp)).toBe(String(elementWithProp.id));
+    });
+
     it('works for nested properties', () => {
       const generator = KeyGenerators.fromPropertyPath("profile.dob.month");
 
@@ -119,6 +151,24 @@ describe('fromPropertyPath', () => {
       expect(generator(elementWithProp)).toBe(String(elementWithProp.id));
     });
 
+    it('works with the number 0', () => {
+      const generator = KeyGenerators.fromPropertyPath(["id"]);
+
+      const elementWithProp = {...testElement};
+      elementWithProp.id = 0;
+
+      expect(generator(elementWithProp)).toBe(String(elementWithProp.id));
+    });
+
+    it('works with the boolean false', () => {
+      const generator = KeyGenerators.fromPropertyPath(["id"]);
+
+      const elementWithProp = {...testElement};
+      elementWithProp.id = false;
+
+      expect(generator(elementWithProp)).toBe(String(elementWithProp.id));
+    });
+
     it('works for nested properties', () => {
       const generator = KeyGenerators.fromPropertyPath(["profile", "dob", "month"]);