Adds 'strategy' option to allow overwriting existing values

Author: webketje

README.md

@@ -11,7 +11,7 @@ A Metalsmith plugin for setting default values to file metadata.
 ## Features
 
 - sets default values for metadata keys and file contents on files matched by pattern
-- does not overwrite or transform key values that are already defined
+- does not overwrite or transform key values that are already defined, unless `strategy: 'overwrite'`.
 - can set computed defaults based on other metadata
 
 ## Installation
@@ -83,6 +83,7 @@ metalsmith.use(
 
 - `pattern` (`string|string[]`): One or more glob patterns to match file paths. Defaults to `'**'` (all).
 - `defaults` (`Object<string, any>`): An object whose key-value pairs will be added to file metadata. You can also specify a function `callback(file)` to set dynamic defaults based on other, existing file metadata.
+- `strategy` (`'keep'|'overwrite'`): Strategy to handle setting defaults to keys that are aleady defined.
 
 ### Examples
 

lib/index.d.ts

@@ -9,6 +9,8 @@ export interface DefaultsSet {
   defaults: {
     [key:string]: string;
   }
+  /** Strategy to handle setting defaults to keys that are aleady defined. */
+  strategy: 'keep'|'overwrite'
 }
 export type Options = DefaultsSet|DefaultsSet[]
 /**

src/index.js

@@ -4,11 +4,13 @@ import set_defaults from './set_defaults.js'
  * @typedef {Object} DefaultsSet
  * @property {string|string[]} [pattern="**"] 1 or more glob patterns to match files. Defaults to `'**'` (all).
  * @property {Object} [defaults={}] an object whose keys will be set as file metadata keys
+ * @property {'keep'|'overwrite'} strategy Strategy to handle setting defaults to keys that are aleady defined.
  */
 
 /** @type {DefaultsSet} */
 const defaultDefaultsSet = {
   defaults: {},
+  strategy: 'keep',
   pattern: '**'
 }
 
@@ -41,12 +43,12 @@ function defaultValues(options) {
     const defaultSets = (options || []).map((defaultsSet) => Object.assign({}, defaultDefaultsSet, defaultsSet))
 
     // Loop through configurations
-    defaultSets.forEach(function ({ pattern, defaults }) {
+    defaultSets.forEach(function ({ pattern, defaults, strategy }) {
       const matches = metalsmith.match(pattern, Object.keys(files))
       debug.info('Matched %s files to pattern "%s": %o', matches.length, pattern, matches)
       if (matches.length) {
         matches.forEach((file) => {
-          set_defaults(defaults)(files[file])
+          set_defaults(defaults, strategy)(files[file])
           debug.info(
             'Defaults set for file "%s", the resulting metadata is: %O',
             file,

src/set_defaults.js

@@ -4,13 +4,19 @@ import set from 'lodash.set'
 /**
  * Sets defaults for object values
  * @param {Object<string, *>} defaults
+ * @param {'keep'|'overwrite'} strategy
  * @return {function} Takes an object and sets defaults
  */
-function set_defaults(defaults) {
+function set_defaults(defaults, strategy) {
   return (item) => {
     Object.keys(defaults).forEach((key) => {
       const value = get(item, key)
-      if (value === void 0 || value === null || (key === 'contents' && item.contents.toString().trim().length === 0)) {
+      if (
+        strategy === 'overwrite' ||
+        value === void 0 ||
+        value === null ||
+        (key === 'contents' && item.contents.toString().trim().length === 0)
+      ) {
         let default_value = defaults[key]
         if (typeof defaults[key] === 'function') default_value = default_value(item)
         set(item, key, default_value)

test/index.cjs

@@ -226,5 +226,24 @@ describe('@metalsmith/default-values', function () {
 
       assert.deepStrictEqual(actual, expected)
     })
+
+
+    it('overwrites a key when strategy is "overwrite"', function () {
+      const defaults = {
+        initial: 'no',
+        default_val: true
+      }
+      const set_defaults = set_defaults_lib(defaults, 'overwrite')
+      assert.strictEqual(typeof set_defaults, 'function', 'Function returned after initialisation')
+      const actual = set_defaults({
+        initial: 'yes'
+      })
+      const expected = {
+        initial: 'no',
+        default_val: true
+      }
+
+      assert.deepStrictEqual(actual, expected)
+    })
   })
 })