Add per field generation (#106)

This PR adds something that would come in super handy for a project I'm working on - in summary:

- You can provide a generator for a field based on its name and its parent `Type`
- You can pass arguments to the generator
- You can call another function (with arguments) on the generator result
- You can provide a locale to the `faker` package

Co-authored-by: Corentin Ardeois <[email protected]>

Author: emab

README.md

@@ -48,49 +48,43 @@ keep all GraphQL names as-is. Available case functions in `change-case-all` are
 `localeLowerCase`, `lowerCaseFirst`, `spongeCase`, `titleCase`, `upperCase`, `localeUpperCase` and `upperCaseFirst`
 [See more](https://github.com/btxtiger/change-case-all)
 
-### scalars (`{ [Scalar: string]: ScalarDefinition }`, defaultValue: `undefined`)
+### scalars (`{ [Scalar: string]: GeneratorOptions }`, defaultValue: `undefined`)
 
 Allows you to define mappings for your custom scalars. Allows you to map any GraphQL Scalar to a
 [casual](https://github.com/boo1ean/casual#embedded-generators) embedded generator (string or
 function key) with optional arguments, or a or [faker](https://fakerjs.dev/api/) generator with optional arguments
 
-Examples using **casual**
+For detailed configuration options, see [GeneratorOptions](#generatoroptions-type) documentation.
 
-**With arguments**
+Examples using **casual**
 
 ```yaml
 plugins:
   - typescript-mock-data:
       scalars:
-        Date: # gets translated to casual.date('YYYY-MM-DD')
-          generator: date
-          arguments: 'YYYY-MM-DD'
+        Date: date # gets translated to casual.date()
 ```
 
-**With multiple arguments**
+**With arguments**
 
 ```yaml
 plugins:
   - typescript-mock-data:
       scalars:
-        PaginatedAmount: # gets translated to casual.integer(-100, 100)
-          generator: integer
-          arguments:
-            - -100
-            - 100
+        Date: # gets translated to casual.date('YYYY-MM-DD')
+          generator: date
+          arguments: 'YYYY-MM-DD'
 ```
 
-**Shorthand if you don't have arguments**
+Examples using **faker**
 
 ```yaml
 plugins:
   - typescript-mock-data:
       scalars:
-        Date: date # gets translated to casual.date()
+        Date: date.past # gets translated to faker.date.past()
 ```
 
-Examples using **faker**
-
 **With arguments**
 
 ```yaml
@@ -102,28 +96,6 @@ plugins:
           arguments: 10
 ```
 
-**With multiple arguments**
-
-```yaml
-plugins:
-  - typescript-mock-data:
-      scalars:
-        Description: # gets translated to faker.lorem.paragraphs(3, '\n')
-          generator: lorem.paragraphs
-          arguments:
-            - 3
-            - '\n'
-```
-
-**Shorthand if you don't have arguments**
-
-```yaml
-plugins:
-  - typescript-mock-data:
-      scalars:
-        Date: date.past # gets translated to faker.date.past()
-```
-
 **Custom value generator**
 
 ```yaml
@@ -181,11 +153,155 @@ When disabled, underscores will be retained for type names when the case is chan
 
 When enabled, values will be generated dynamically when the mock function is called rather than statically when the mock function is generated. The values are generated consistently from a [casual seed](https://github.com/boo1ean/casual#seeding) that can be manually configured using the generated `seedMocks(seed: number)` function, as shown in [this test](https://github.com/JimmyPaolini/graphql-codegen-typescript-mock-data/blob/dynamic-mode/tests/dynamicValues/spec.ts#L13).
 
+### fieldGeneration (`{ [typeName: string]: { [fieldName: string]: GeneratorOptions } }`, defaultValue: `undefined`)
+
+This setting allows you to add specific generation to a field for a given type. For example if you have a type called `User` and a field called `birthDate` you can override any generated value there as follows:
+
+```yaml
+plugins:
+  - typescript-mock-data:
+      scalars:
+        Date: date.future
+      fieldGeneration:
+        User:
+          birthDate: date.past
+```
+
+Note that even if `birthDate` is a scalar of `Date` type, its value will still be overridden.
+
+If you want to use a specific generator for **all** fields of a given name, you can declare it under a property called `_all`:
+
+```yaml
+plugins:
+  - typescript-mock-data:
+      scalars:
+        Date: date.future
+      fieldGeneration:
+        _all:
+          email: internet.email
+        AdminUser:
+          email: '[email protected]'
+```
+
+In the above example all resolvers with the name `email` will use the `internet.email` generator. However since we specified a specific email for `AdminUser` that will take precedence over the `_all` generated value.
+
+For detailed configuration options, see [GeneratorOptions](#generatoroptions-type) documentation.
+
 ### generateLibrary (`'casual' | 'faker'`, defaultValue: `'casual'`)
 
 Select a library to generate mock values. The default is [casual](https://github.com/boo1ean/casual), Other options include [faker](https://github.com/faker-js/faker).
 casual dependents on Node API and cannot be executed in a browser. faker is useful when you want to use a mock function with the dynamicValues option enabled in the browser.
 
+### `GeneratorOptions` type
+
+This type is used in `scalars` and `fieldGeneration` options.
+
+Examples using **casual**
+
+**Shorthand if you don't have arguments**
+
+```yaml
+fieldName: date # gets translated to casual.date()
+```
+
+**With arguments**
+
+```yaml
+fieldName: # gets translated to casual.date('YYYY-MM-DD')
+  generator: date
+  arguments: 'YYYY-MM-DD'
+```
+
+**With multiple arguments**
+
+```yaml
+fieldName: # gets translated to casual.integer(-100, 100)
+  generator: integer
+  arguments:
+    - -100
+    - 100
+```
+
+**With extra function call**
+
+```yaml
+fieldName: # gets translated to casual.integer.toFixed()
+  generator: integer
+  extra:
+    function: toFixed
+```
+
+**With extra function call arguments**
+
+```yaml
+fieldName: # gets translated to casual.integer.toFixed(3)
+  generator: integer
+  extra:
+    function: toFixed
+    arguments: 3
+```
+
+Examples using **faker**
+
+**With arguments**
+
+```yaml
+plugins:
+  - typescript-mock-data:
+      scalars:
+        Date: # gets translated to faker.date.past(10)
+          generator: date.past
+          arguments: 10
+```
+
+**With multiple arguments**
+
+```yaml
+plugins:
+  - typescript-mock-data:
+      scalars:
+        Description: # gets translated to faker.lorem.paragraphs(3, '\n')
+          generator: lorem.paragraphs
+          arguments:
+            - 3
+            - '\n'
+```
+
+**Shorthand if you don't have arguments**
+
+```yaml
+plugins:
+  - typescript-mock-data:
+      scalars:
+        Date: date.past # gets translated to faker.date.past()
+```
+
+**With extra function call**
+
+```yaml
+fieldName: # gets translated to casual.date().toLocaleDateString()
+  generator: date
+  extra:
+    function: toLocaleDateString
+```
+
+**With extra function call arguments**
+
+```yaml
+fieldName: # gets translated to casual.date().toLocaleDateString('en_GB)
+  generator: date
+  extra:
+    function: toLocaleDateString
+    arguments: 'en_GB'
+```
+
+**Custom value generator**
+
+```yaml
+# gets translated as is
+fieldName: arrayBufferGenerator()
+```
+
 ## Examples of usage
 
 **codegen.yml**

package.json

@@ -62,7 +62,7 @@
     "sideEffects": false,
     "scripts": {
         "build": "tsc -m esnext --outDir dist/esnext && tsc -m commonjs --outDir dist/commonjs",
-        "test": "TZ=UTC jest",
+        "test": "TZ=UTC LANG=en_US.UTF8 jest",
         "lint": "eslint 'src/**/*.{js,ts,tsx}' --quiet --fix && tsc --noEmit",
         "prettify": "prettier --config ./.prettierrc.js --write",
         "auto:version": "yarn version --`auto version` --message 'Bump version to: %s [skip ci]'",