feat(helpers): fake from array (#1453)

Author: ST-DDT

src/modules/company/index.ts

@@ -36,11 +36,9 @@ export class CompanyModule {
    * @since 7.4.0
    */
   name(): string {
-    const pattern = this.faker.helpers.arrayElement(
+    return this.faker.helpers.fake(
       this.faker.definitions.company.name_patterns
     );
-
-    return this.faker.helpers.fake(pattern);
   }
 
   /**

src/modules/helpers/index.ts

@@ -506,7 +506,7 @@ export class HelpersModule {
    * It checks the given string for placeholders and replaces them by calling faker methods:
    *
    * ```js
-   * const hello = faker.helpers.fake('Hi, my name is {{person.firstName}} {{person.lastName}}!')
+   * const hello = faker.helpers.fake('Hi, my name is {{person.firstName}} {{person.lastName}}!');
    * ```
    *
    * This would use the `faker.person.firstName()` and `faker.person.lastName()` method to resolve the placeholders respectively.
@@ -515,18 +515,18 @@ export class HelpersModule {
    * and if that isn't possible, we will fall back to string:
    *
    * ```js
-   * const message = faker.helpers.fake('You can call me at {{phone.number(+!# !## #### #####!)}}.')
+   * const message = faker.helpers.fake('You can call me at {{phone.number(+!# !## #### #####!)}}.');
    * ```
    *
    * It is also possible to use multiple parameters (comma separated).
    *
    * ```js
-   * const message = faker.helpers.fake('Your pin is {{string.numeric(4, {"allowLeadingZeros": true})}}.')
+   * const message = faker.helpers.fake('Your pin is {{string.numeric(4, {"allowLeadingZeros": true})}}.');
    * ```
    *
-   * It is also NOT possible to use any non-faker methods or plain javascript in such templates.
+   * It is also NOT possible to use any non-faker methods or plain javascript in such patterns.
    *
-   * @param str The template string that will get interpolated. Must not be empty.
+   * @param pattern The pattern string that will get interpolated. Must not be empty.
    *
    * @see faker.helpers.mustache() to use custom functions for resolution.
    *
@@ -541,24 +541,127 @@ export class HelpersModule {
    *
    * @since 7.4.0
    */
-  fake(str: string): string {
+  fake(pattern: string): string;
+  /**
+   * Generator for combining faker methods based on an array containing static string inputs.
+   *
+   * Note: We recommend using string template literals instead of `fake()`,
+   * which are faster and strongly typed (if you are using TypeScript),
+   * e.g. ``const address = `${faker.location.zipCode()} ${faker.location.city()}`;``
+   *
+   * This method is useful if you have to build a random string from a static, non-executable source
+   * (e.g. string coming from a user, stored in a database or a file).
+   *
+   * It checks the given string for placeholders and replaces them by calling faker methods:
+   *
+   * ```js
+   * const hello = faker.helpers.fake(['Hi, my name is {{person.firstName}} {{person.lastName}}!']);
+   * ```
+   *
+   * This would use the `faker.person.firstName()` and `faker.person.lastName()` method to resolve the placeholders respectively.
+   *
+   * It is also possible to provide parameters. At first, they will be parsed as json,
+   * and if that isn't possible, it will fall back to string:
+   *
+   * ```js
+   * const message = faker.helpers.fake([
+   *   'You can call me at {{phone.number(+!# !## #### #####!)}}.',
+   *   'My email is {{internet.email}}.',
+   * ]);
+   * ```
+   *
+   * It is also possible to use multiple parameters (comma separated).
+   *
+   * ```js
+   * const message = faker.helpers.fake(['Your pin is {{string.numeric(4, {"allowLeadingZeros": true})}}.']);
+   * ```
+   *
+   * It is also NOT possible to use any non-faker methods or plain javascript in such patterns.
+   *
+   * @param patterns The array to select a pattern from, that will then get interpolated. Must not be empty.
+   *
+   * @see faker.helpers.mustache() to use custom functions for resolution.
+   *
+   * @example
+   * faker.helpers.fake(['A: {{person.firstName}}', 'B: {{person.lastName}}']) // 'A: Barry'
+   *
+   * @since 8.0.0
+   */
+  fake(patterns: string[]): string;
+  /**
+   * Generator for combining faker methods based on a static string input or an array of static string inputs.
+   *
+   * Note: We recommend using string template literals instead of `fake()`,
+   * which are faster and strongly typed (if you are using TypeScript),
+   * e.g. ``const address = `${faker.location.zipCode()} ${faker.location.city()}`;``
+   *
+   * This method is useful if you have to build a random string from a static, non-executable source
+   * (e.g. string coming from a user, stored in a database or a file).
+   *
+   * It checks the given string for placeholders and replaces them by calling faker methods:
+   *
+   * ```js
+   * const hello = faker.helpers.fake('Hi, my name is {{person.firstName}} {{person.lastName}}!');
+   * ```
+   *
+   * This would use the `faker.person.firstName()` and `faker.person.lastName()` method to resolve the placeholders respectively.
+   *
+   * It is also possible to provide parameters. At first, they will be parsed as json,
+   * and if that isn't possible, it will fall back to string:
+   *
+   * ```js
+   * const message = faker.helpers.fake('You can call me at {{phone.number(+!# !## #### #####!)}}.');
+   * ```
+   *
+   * It is also possible to use multiple parameters (comma separated).
+   *
+   * ```js
+   * const message = faker.helpers.fake('Your pin is {{string.numeric(4, {"allowLeadingZeros": true})}}.');
+   * ```
+   *
+   * It is also NOT possible to use any non-faker methods or plain javascript in such patterns.
+   *
+   * @param pattern The pattern string that will get interpolated. Must not be empty. If an array is passed, a random element will be picked and interpolated.
+   *
+   * @see faker.helpers.mustache() to use custom functions for resolution.
+   *
+   * @example
+   * faker.helpers.fake('{{person.lastName}}') // 'Barrows'
+   * faker.helpers.fake('{{person.lastName}}, {{person.firstName}} {{person.suffix}}') // 'Durgan, Noe MD'
+   * faker.helpers.fake('This is static test.') // 'This is static test.'
+   * faker.helpers.fake('Good Morning {{person.firstName}}!') // 'Good Morning Estelle!'
+   * faker.helpers.fake('You can call me at {{phone.number(!## ### #####!)}}.') // 'You can call me at 202 555 973722.'
+   * faker.helpers.fake('I flipped the coin and got: {{helpers.arrayElement(["heads", "tails"])}}') // 'I flipped the coin and got: tails'
+   * faker.helpers.fake(['A: {{person.firstName}}', 'B: {{person.lastName}}']) // 'A: Barry'
+   *
+   * @since 7.4.0
+   */
+  fake(pattern: string | string[]): string;
+  fake(pattern: string | string[]): string {
+    if (Array.isArray(pattern)) {
+      pattern = this.arrayElement(pattern);
+      // TODO @ST-DDT 2022-10-15: Remove this check after we fail in `arrayElement` when the array is empty
+      if (pattern == null) {
+        throw new FakerError('Array of pattern strings cannot be empty.');
+      }
+    }
     // if incoming str parameter is not provided, return error message
-    if (typeof str !== 'string' || str.length === 0) {
-      throw new FakerError('string parameter is required!');
+    if (pattern.length === 0) {
+      throw new FakerError('Pattern string cannot be empty.');
     }
 
     // find first matching {{ and }}
-    const start = str.search(/{{[a-z]/);
-    const end = str.indexOf('}}', start);
+    const start = pattern.search(/{{[a-z]/);
+    const end = pattern.indexOf('}}', start);
 
     // if no {{ and }} is found, we are done
     if (start === -1 || end === -1) {
-      return str;
+      return pattern;
     }
 
     // extract method name from between the {{ }} that we found
     // for example: {{person.firstName}}
-    const token = str.substring(start + 2, end + 2);
+    const token = pattern.substring(start + 2, end + 2);
     let method = token.replace('}}', '').replace('{{', '');
 
     // extract method parameters
@@ -615,7 +718,8 @@ export class HelpersModule {
 
     // Replace the found tag with the returned fake value
     // We cannot use string.replace here because the result might contain evaluated characters
-    const res = str.substring(0, start) + result + str.substring(end + 2);
+    const res =
+      pattern.substring(0, start) + result + pattern.substring(end + 2);
 
     if (res === '') {
       return '';

src/modules/location/index.ts

@@ -75,10 +75,7 @@ export class LocationModule {
    * @since 8.0.0
    */
   city(): string {
-    const pattern = this.faker.helpers.arrayElement(
-      this.faker.definitions.location.city
-    );
-    return this.faker.helpers.fake(pattern);
+    return this.faker.helpers.fake(this.faker.definitions.location.city);
   }
 
   /**
@@ -121,10 +118,7 @@ export class LocationModule {
    * @since 8.0.0
    */
   street(): string {
-    const format = this.faker.helpers.arrayElement(
-      this.faker.definitions.location.street
-    );
-    return this.faker.helpers.fake(format);
+    return this.faker.helpers.fake(this.faker.definitions.location.street);
   }
 
   /**

test/__snapshots__/helpers.spec.ts.snap

@@ -29,9 +29,13 @@ exports[`helpers > 42 > arrayElements > with array and count 1`] = `
 ]
 `;
 
-exports[`helpers > 42 > fake > with args 1`] = `"my string: Cky2eiXX/J"`;
+exports[`helpers > 42 > fake > with a dynamic template 1`] = `"my string: Cky2eiXX/J"`;
 
-exports[`helpers > 42 > fake > with plain string 1`] = `"my test string"`;
+exports[`helpers > 42 > fake > with a static template 1`] = `"my test string"`;
+
+exports[`helpers > 42 > fake > with multiple dynamic templates 1`] = `"Sandy"`;
+
+exports[`helpers > 42 > fake > with multiple static templates 1`] = `"B"`;
 
 exports[`helpers > 42 > maybe > with only value 1`] = `"Hello World!"`;
 
@@ -208,9 +212,13 @@ exports[`helpers > 1211 > arrayElements > with array and count 1`] = `
 ]
 `;
 
-exports[`helpers > 1211 > fake > with args 1`] = `"my string: wKti5-}$_/"`;
+exports[`helpers > 1211 > fake > with a dynamic template 1`] = `"my string: wKti5-}$_/"`;
+
+exports[`helpers > 1211 > fake > with a static template 1`] = `"my test string"`;
 
-exports[`helpers > 1211 > fake > with plain string 1`] = `"my test string"`;
+exports[`helpers > 1211 > fake > with multiple dynamic templates 1`] = `"La Crosse"`;
+
+exports[`helpers > 1211 > fake > with multiple static templates 1`] = `"C"`;
 
 exports[`helpers > 1211 > maybe > with only value 1`] = `undefined`;
 
@@ -383,9 +391,13 @@ exports[`helpers > 1337 > arrayElements > with array and count 1`] = `
 ]
 `;
 
-exports[`helpers > 1337 > fake > with args 1`] = `"my string: 9U/4:SK$>6"`;
+exports[`helpers > 1337 > fake > with a dynamic template 1`] = `"my string: 9U/4:SK$>6"`;
+
+exports[`helpers > 1337 > fake > with a static template 1`] = `"my test string"`;
+
+exports[`helpers > 1337 > fake > with multiple dynamic templates 1`] = `"U/4:SK$>6Q"`;
 
-exports[`helpers > 1337 > fake > with plain string 1`] = `"my test string"`;
+exports[`helpers > 1337 > fake > with multiple static templates 1`] = `"A"`;
 
 exports[`helpers > 1337 > maybe > with only value 1`] = `"Hello World!"`;
 

test/helpers.spec.ts

@@ -96,10 +96,14 @@ describe('helpers', () => {
     });
 
     t.describe('fake', (t) => {
-      t.it('with plain string', 'my test string').it(
-        'with args',
-        'my string: {{datatype.string}}'
-      );
+      t.it('with a static template', 'my test string')
+        .it('with a dynamic template', 'my string: {{string.sample}}')
+        .it('with multiple static templates', ['A', 'B', 'C'])
+        .it('with multiple dynamic templates', [
+          '{{string.sample}}',
+          '{{location.city_name}}',
+          '{{location.cityName}}',
+        ]);
     });
 
     t.describe('rangeToNumber', (t) => {
@@ -598,11 +602,16 @@ describe('helpers', () => {
           expect(actual).toMatch(/^\d{5}$/);
         });
 
-        it('does not allow undefined parameters', () => {
-          expect(() =>
-            // @ts-expect-error: The parameter is required
-            faker.helpers.fake()
-          ).toThrowError(new FakerError('string parameter is required!'));
+        it('does not allow empty string parameters', () => {
+          expect(() => faker.helpers.fake('')).toThrowError(
+            new FakerError('Pattern string cannot be empty.')
+          );
+        });
+
+        it('does not allow empty array parameters', () => {
+          expect(() => faker.helpers.fake([])).toThrowError(
+            new FakerError('Array of pattern strings cannot be empty.')
+          );
         });
 
         it('does not allow invalid module name', () => {
@@ -655,6 +664,21 @@ describe('helpers', () => {
           );
         });
 
+        it('should be able to pass multiple static templates', () => {
+          expect(['A', 'B', 'C']).toContain(
+            faker.helpers.fake(['A', 'B', 'C'])
+          );
+        });
+
+        it('should be able to pass multiple dynamic templates', () => {
+          expect(faker.definitions.location.city_name).toContain(
+            faker.helpers.fake([
+              '{{location.city_name}}',
+              '{{location.cityName}}',
+            ])
+          );
+        });
+
         it('should be able to handle only {{ brackets', () => {
           expect(faker.helpers.fake('{{hello')).toBe('{{hello');
           expect(faker.helpers.fake('hello{{')).toBe('hello{{');