Provides access to metalsmith.metadata() within default setter functions

README.md

@@ -12,7 +12,7 @@ A Metalsmith plugin for setting default values to file metadata.
 
 - 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, unless `strategy: 'overwrite'`.
-- can set computed defaults based on other metadata
+- can set computed defaults based on other file keys or metalsmith metadata
 
 ## Installation
 
@@ -82,7 +82,7 @@ metalsmith.use(
 `@metalsmith/default-values` takes an array of defaults sets or a single defaults set. The defaults set has the following properties:
 
 - `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.
+- `defaults` (`Object<string, any>`): An object whose key-value pairs will be added to file metadata. You can also specify a function `callback(file, metadata)` to set dynamic defaults based on existing file or global metadata.
 - `strategy` (`'keep'|'overwrite'`): Strategy to handle setting defaults to keys that are aleady defined.
 
 ### Examples
@@ -100,6 +100,32 @@ metalsmith.use(
 )
 ```
 
+#### Setting dynamic defaults
+
+You can set dynamic defaults based on current file metadata or metalsmith metadata:
+
+```js
+metalsmith
+  .metadata({
+    build: { timestamp: Date.now() }
+  })
+  .use(
+    defaultValues([
+      {
+        strategy: 'overwrite',
+        defaults: {
+          buildInfo(file, metadata) {
+            return metadata.build
+          },
+          excerpt(file) {
+            return file.contents.toString().slice(0, 200)
+          }
+        }
+      }
+    ])
+  )
+```
+
 #### Combining with other plugins
 
 @metalsmith/default-values works great with other `@metalsmith` plugins. The example below attaches a collection and layout matching the parent directory for all files in the directories `services`,`products`, and `articles`:

lib/index.d.ts

@@ -1,13 +1,12 @@
-import { Plugin } from 'metalsmith';
-import defaultValues from '.';
+import { Plugin, File } from 'metalsmith';
 
 export default defaultValues;
 export interface DefaultsSet {
   /** 1 or more glob patterns to match files. Defaults to `'**'` (all). */
   pattern?: string;
   /** an object whose keys will be set as file metadata keys */
   defaults: {
-    [key:string]: string;
+    [key:string]: ((data:File, metadata: {[key:string]:any}) => any)|string|boolean|number|Object;
   }
   /** Strategy to handle setting defaults to keys that are aleady defined. */
   strategy: 'keep'|'overwrite'

src/index.js

@@ -1,9 +1,15 @@
 import getDefaultsSetter from './set_defaults.js'
 
+/**
+ * @callback DefaultSetter
+ * @param {import('metalsmith').File} file
+ * @param {Object<string, *>} metadata
+ */
+
 /**
  * @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 {Object<string, *>} [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.
  */
 
@@ -50,7 +56,7 @@ function defaultValues(options) {
       if (matches.length) {
         const setDefaults = getDefaultsSetter(defaultsEntries, strategy)
         matches.forEach((file) => {
-          setDefaults(files[file])
+          setDefaults(files[file], metalsmith.metadata())
           debug.info(
             'Defaults set for file "%s", the resulting metadata is: %O',
             file,

src/set_defaults.js

@@ -5,10 +5,10 @@ import { dset as set } from 'dset'
  * Sets defaults for object values
  * @param {Array<Array<*>>} defaults
  * @param {'keep'|'overwrite'} strategy
- * @return {function} Takes an object and sets defaults
+ * @return {import('.').DefaultSetter} Takes an object and sets defaults
  */
 function set_defaults(defaults, strategy) {
-  return (item) => {
+  return (item, context) => {
     defaults.forEach(([key, defaultValue]) => {
       const value = get(item, key)
       if (
@@ -17,7 +17,7 @@ function set_defaults(defaults, strategy) {
         value === null ||
         (key === 'contents' && item.contents.toString().trim().length === 0)
       ) {
-        if (typeof defaultValue === 'function') defaultValue = defaultValue(item)
+        if (typeof defaultValue === 'function') defaultValue = defaultValue(item, context)
         set(item, key, defaultValue)
       }
     })

test/index.cjs

@@ -22,7 +22,7 @@ function relevantProps(expected, files) {
 }
 
 describe('@metalsmith/default-values', function () {
-  before(function(done) {
+  before(function (done) {
     // eslint-disable-next-line import/no-internal-modules
     import('../src/set_defaults.js').then(imported => {
       set_defaults_lib = imported.default
@@ -85,11 +85,11 @@ describe('@metalsmith/default-values', function () {
 
   it('logs a warning when no files match a pattern', function (done) {
     let warning
-    function Debugger() {}
+    function Debugger() { }
     Debugger.warn = (msg) => {
       warning = msg
     }
-    Debugger.info = () => {}
+    Debugger.info = () => { }
 
     const msStub = {
       match() {
@@ -245,5 +245,22 @@ describe('@metalsmith/default-values', function () {
 
       assert.deepStrictEqual(actual, expected)
     })
+
+    it('sets a default computed from additional metadata', function () {
+      const defaults = {
+        default_val: true, buildVersion(file, globalMeta) {
+          return globalMeta.buildVersion
+        }
+      }
+      const set_defaults = set_defaults_lib(Object.entries(defaults))
+      const actual = set_defaults({ initial: 'yes' }, { buildVersion: '1.0.0' })
+      const expected = {
+        initial: 'yes',
+        default_val: true,
+        buildVersion: '1.0.0'
+      }
+
+      assert.deepStrictEqual(actual, expected)
+    })
   })
 })