fromJSON and toJSON

lib/fromJSON.js

@@ -0,0 +1,46 @@
+'use strict'
+
+let Declaration = require('./declaration')
+let Comment = require('./comment')
+let AtRule = require('./at-rule')
+let Root = require('./root')
+let Rule = require('./rule')
+let Input = require('./input')
+let PreviousMap = require('./previous-map')
+
+function fromJSON (json) {
+  let defaults = { ...json }
+  if (json.nodes) {
+    defaults.nodes = json.nodes.map(n => fromJSON(n))
+  }
+  if (json.type === 'root') {
+    if (defaults.source) {
+      defaults.source = { ...defaults.source }
+      if (defaults.source.input) {
+        defaults.source.input = {
+          ...defaults.source.input,
+          __proto__: Input.prototype
+        }
+        if (defaults.source.input.map) {
+          defaults.source.input.map = {
+            ...defaults.source.input.map,
+            __proto__: PreviousMap.prototype
+          }
+        }
+      }
+    }
+    return new Root(defaults)
+  } else if (json.type === 'decl') {
+    return new Declaration(defaults)
+  } else if (json.type === 'rule') {
+    return new Rule(defaults)
+  } else if (json.type === 'comment') {
+    return new Comment(defaults)
+  } else if (json.type === 'atrule') {
+    return new AtRule(defaults)
+  } else {
+    throw new Error('Unknown node type ' + json.type)
+  }
+}
+
+module.exports = fromJSON

lib/input.js

@@ -49,42 +49,41 @@ class Input {
   }
 
   fromOffset (offset) {
-    let lines = this.css.split('\n')
-    let lineToIndex = new Array(lines.length)
-    let prevIndex = 0
+    if (!this.lineToIndex) {
+      let lines = this.css.split('\n')
+      this.lineToIndex = new Array(lines.length)
+      let prevIndex = 0
+
+      for (let i = 0, l = lines.length; i < l; i++) {
+        this.lineToIndex[i] = prevIndex
+        prevIndex += lines[i].length + 1
+      }
 
-    for (let i = 0, l = lines.length; i < l; i++) {
-      lineToIndex[i] = prevIndex
-      prevIndex += lines[i].length + 1
+      this.lastLine = this.lineToIndex[this.lineToIndex.length - 1]
     }
 
-    let lastLine = lineToIndex[lineToIndex.length - 1]
-
-    this.fromOffset = index => {
-      let min = 0
-      if (index >= lastLine) {
-        min = lineToIndex.length - 1
-      } else {
-        let max = lineToIndex.length - 2
-        let mid
-        while (min < max) {
-          mid = min + ((max - min) >> 1)
-          if (index < lineToIndex[mid]) {
-            max = mid - 1
-          } else if (index >= lineToIndex[mid + 1]) {
-            min = mid + 1
-          } else {
-            min = mid
-            break
-          }
+    let min = 0
+    if (offset >= this.lastLine) {
+      min = this.lineToIndex.length - 1
+    } else {
+      let max = this.lineToIndex.length - 2
+      let mid
+      while (min < max) {
+        mid = min + ((max - min) >> 1)
+        if (offset < this.lineToIndex[mid]) {
+          max = mid - 1
+        } else if (offset >= this.lineToIndex[mid + 1]) {
+          min = mid + 1
+        } else {
+          min = mid
+          break
         }
       }
-      return {
-        line: min + 1,
-        col: index - lineToIndex[min] + 1
-      }
     }
-    return this.fromOffset(offset)
+    return {
+      line: min + 1,
+      col: offset - this.lineToIndex[min] + 1
+    }
   }
 
   error (message, line, column, opts = {}) {
@@ -168,6 +167,21 @@ class Input {
   get from () {
     return this.file || this.id
   }
+
+  toJSON () {
+    let json = {}
+    if (this.hasBOM != null) json.hasBOM = this.hasBOM
+    if (this.css != null) json.css = this.css
+    if (this.file != null) json.file = this.file
+    if (this.id != null) json.id = this.id
+    if (this.map) {
+      json.map = { ...this.map }
+      if (json.map.consumerCache) {
+        json.map.consumerCache = undefined
+      }
+    }
+    return json
+  }
 }
 
 module.exports = Input

lib/node.js

@@ -187,6 +187,11 @@ class Node {
         })
       } else if (typeof value === 'object' && value.toJSON) {
         fixed[name] = value.toJSON()
+      } else if (this.type === 'root' && name === 'source') {
+        fixed[name] = {
+          input: value.input.toJSON(),
+          start: value.start
+        }
       } else {
         fixed[name] = value
       }

lib/postcss.d.ts

@@ -397,6 +397,12 @@ export interface Postcss {
    */
   root(defaults?: RootProps): Root
 
+  /**
+   * Rehydrate a JSON AST (from Node#toJSON) back into the corresponding node.
+   * @param data A JSON AST.
+   */
+  fromJSON(data: object): Node
+
   CssSyntaxError: typeof CssSyntaxError
   Declaration: typeof Declaration
   Container: typeof Container
@@ -412,6 +418,7 @@ export interface Postcss {
 
 export const stringify: Stringifier
 export const parse: Parser
+export const fromJSON: Postcss['fromJSON']
 
 export const comment: Postcss['comment']
 export const atRule: Postcss['atRule']

lib/postcss.js

@@ -12,6 +12,7 @@ let AtRule = require('./at-rule')
 let Result = require('./result.js')
 let Input = require('./input')
 let parse = require('./parse')
+let fromJSON = require('./fromJSON')
 let list = require('./list')
 let Rule = require('./rule')
 let Root = require('./root')
@@ -62,6 +63,7 @@ postcss.plugin = function plugin (name, initializer) {
 
 postcss.stringify = stringify
 postcss.parse = parse
+postcss.fromJSON = fromJSON
 postcss.list = list
 
 postcss.comment = defaults => new Comment(defaults)

lib/postcss.mjs

@@ -5,6 +5,7 @@ export default postcss
 export const stringify = postcss.stringify
 export const plugin = postcss.plugin
 export const parse = postcss.parse
+export const fromJSON = postcss.fromJSON
 export const list = postcss.list
 
 export const comment = postcss.comment

test/fromJSON.test.ts

@@ -0,0 +1,28 @@
+import v8 from 'v8'
+
+import postcss, { Root } from '../lib/postcss.js'
+
+it('can rehydrate a JSON AST', () => {
+  let cssWithMap = postcss().process(
+    '.foo { color: red; font-size: 12pt; } /* abc */ @media (width: 60em) { }',
+    {
+      from: undefined,
+      map: {
+        inline: true
+      },
+      stringifier: postcss.stringify
+    }
+  ).css
+
+  let root = postcss.parse(cssWithMap)
+
+  let json = root.toJSON()
+  let serialized = v8.serialize(json)
+  let deserialized = v8.deserialize(serialized)
+  // @ts-ignore
+  let rehydrated: Root = postcss.fromJSON(deserialized)
+
+  rehydrated.nodes[0].remove()
+
+  expect(rehydrated.nodes).toHaveLength(3)
+})