Add JSDoc based types

.gitignore

@@ -1,4 +1,5 @@
 .DS_Store
+*.d.ts
 *.log
 coverage/
 node_modules/

index.js

@@ -1,64 +1,142 @@
+/**
+ * @typedef {import('assert').AssertionError} AssertionError
+ * @typedef {import('unist').Node} Node
+ * @typedef {import('unist').Parent} Parent
+ * @typedef {import('unist').Literal} Literal
+ * @typedef {import('unist').Position} Position
+ * @typedef {import('unist').Point} Point
+ * @typedef {Node & {children: never, value: never}} Void
+ */
+
 import nodeAssert from 'assert'
 import {inspect} from './inspect.js'
 
-export var assert = wrap(assertNode)
-assert.parent = wrap(parent)
-assert.text = wrap(text)
-assert.void = wrap(empty)
+var own = {}.hasOwnProperty
+
+/**
+ * Assert that `node` is a valid unist node.
+ * If `node` is a parent, all children will be asserted too.
+ *
+ * @param {unknown} [node]
+ * @param {Parent} [parent]
+ * @returns {asserts node is Node}
+ */
+export function assert(node, parent) {
+  return wrap(assertNode)(node, parent)
+}
+
+/**
+ * Assert that `node` is a valid unist parent.
+ * All children will be asserted too.
+ *
+ * @param {unknown} [node]
+ * @param {Parent} [parent]
+ * @returns {asserts node is Parent}
+ */
+export function parent(node, parent) {
+  return wrap(assertParent)(node, parent)
+}
+
+/**
+ * Assert that `node` is a valid unist literal.
+ *
+ * @param {unknown} [node]
+ * @param {Parent} [parent]
+ * @returns {asserts node is Literal}
+ */
+export function literal(node, parent) {
+  return wrap(assertLiteral)(node, parent)
+}
+
+/**
+ * Assert that `node` is a valid unist node, but neither parent nor literal.
+ *
+ * @param {unknown} [node]
+ * @param {Parent} [parent]
+ * @returns {asserts node is Void}
+ */
+export function _void(node, parent) {
+  return wrap(assertVoid)(node, parent)
+}
 
 // Identifier to check if a value is seen.
 var ID = '__unist__'
 
 // List of specced properties.
 var defined = new Set(['type', 'value', 'children', 'position'])
 
-// Wrapper around `Node` which adds the current node (and parent, if available),
-// to the message.
+/**
+ * Wrapper that adds the current node (and parent, if available) to error
+ * messages.
+ *
+ * @param {(node?: unknown, parent?: Parent|null) => asserts node is Node} fn
+ * @returns {(node?: unknown, parent?: Parent|null) => asserts node is Node}
+ */
 export function wrap(fn) {
   return wrapped
 
+  /**
+   * @param {unknown} node
+   * @param {Parent} [parent]
+   * @throws {AssertionError}
+   * @returns {asserts node is T}
+   */
   function wrapped(node, parent) {
     try {
       fn(node, parent)
     } catch (error) {
-      if (!error[ID]) {
+      if (!own.call(error, ID)) {
         error[ID] = true
-
         error.message += ': `' + view(node) + '`'
-
-        if (parent) {
-          error.message += ' in `' + view(parent) + '`'
-        }
+        if (parent) error.message += ' in `' + view(parent) + '`'
       }
 
       throw error
     }
   }
 }
 
-// Assert.
+/**
+ * Assert.
+ *
+ * @param {unknown} node
+ * @returns {asserts node is Node}
+ */
 function assertNode(node) {
-  var type
-  var children
-  var value
+  var index = -1
+  /** @type {Parent} */
+  var parent
+  /** @type {unknown} */
+  var child
+  /** @type {string} */
   var key
-  var index
-  var length
-
-  nodeAssert.ok(node === Object(node), 'node should be an object')
 
-  type = node.type
-  children = node.children
-  value = node.value
+  nodeAssert.ok(
+    node && typeof node === 'object' && !Array.isArray(node),
+    'node should be an object'
+  )
 
-  nodeAssert.ok('type' in node, 'node should have a type')
-  nodeAssert.strictEqual(typeof type, 'string', '`type` should be a string')
-  nodeAssert.notStrictEqual(type, '', '`type` should not be empty')
+  nodeAssert.ok(own.call(node, 'type'), 'node should have a type')
+  nodeAssert.strictEqual(
+    // @ts-expect-error Looks like an indexed object.
+    typeof node.type,
+    'string',
+    '`type` should be a string'
+  )
+  // @ts-expect-error Looks like an indexed object.
+  nodeAssert.notStrictEqual(node.type, '', '`type` should not be empty')
 
-  if (value !== null && value !== undefined) {
-    nodeAssert.strictEqual(typeof value, 'string', '`value` should be a string')
+  // @ts-expect-error Looks like an indexed object.
+  if (node.value !== null && node.value !== undefined) {
+    nodeAssert.strictEqual(
+      // @ts-expect-error Looks like an indexed object.
+      typeof node.value,
+      'string',
+      '`value` should be a string'
+    )
   }
 
+  // @ts-expect-error Looks like an indexed object.
   position(node.position)
 
   for (key in node) {
@@ -67,19 +145,30 @@ function assertNode(node) {
     }
   }
 
-  if (children !== null && children !== undefined) {
-    nodeAssert.ok(Array.isArray(children), '`children` should be an array')
+  // @ts-expect-error Looks like an indexed object.
+  if (node.children !== null && node.children !== undefined) {
+    // @ts-expect-error Looks like parent.
+    parent = node
+    nodeAssert.ok(
+      Array.isArray(parent.children),
+      '`children` should be an array'
+    )
     index = -1
-    length = children.length
 
-    while (++index < length) {
-      assert(children[index], node)
+    while (++index < parent.children.length) {
+      child = parent.children[index]
+      assert(child, parent)
     }
   }
 }
 
-// Assert `value` (which lives at `key`) can be stringified and re-parsed to the
-// same (deep) value.
+/**
+ * Assert `value` (which lives at `key`) can be stringified and re-parsed to the
+ * same (deep) value.
+ *
+ * @param {string} key
+ * @param {unknown} value
+ */
 function vanilla(key, value) {
   try {
     nodeAssert.deepStrictEqual(value, JSON.parse(JSON.stringify(value)))
@@ -88,8 +177,13 @@ function vanilla(key, value) {
   }
 }
 
-// Stringify a value to inspect it.
-// Tries `JSON.stringify()`, and if that fails uses `String()` instead.
+/**
+ * Stringify a value to inspect it.
+ * Tries `JSON.stringify()`, and if that fails uses `String()` instead.
+ *
+ * @param {unknown} value
+ * @returns {string}
+ */
 function view(value) {
   try {
     return inspect(value)
@@ -99,8 +193,13 @@ function view(value) {
   }
 }
 
-// Assert `node` is a parent node.
-function parent(node) {
+/**
+ * Assert `node` is a parent node.
+ *
+ * @param {Node} node
+ * @returns {asserts node is Parent}
+ */
+function assertParent(node) {
   assertNode(node)
 
   nodeAssert.strictEqual(
@@ -111,20 +210,30 @@ function parent(node) {
   nodeAssert.ok('children' in node, 'parent should have `children`')
 }
 
-// Assert `node` is a text node.
-function text(node) {
+/**
+ * Assert `node` is a literal node.
+ *
+ * @param {Node} node
+ * @returns {asserts node is Literal}
+ */
+function assertLiteral(node) {
   assertNode(node)
 
   nodeAssert.strictEqual(
     'children' in node,
     false,
-    'text should not have `children`'
+    'literal should not have `children`'
   )
-  nodeAssert.ok('value' in node, 'text should have `value`')
+  nodeAssert.ok('value' in node, 'literal should have `value`')
 }
 
-// Assert `node` is a unist node, but neither parent nor text.
-function empty(node) {
+/**
+ * Assert `node` is a unist node, but neither parent nor literal.
+ *
+ * @param {Node} node
+ * @returns {asserts node is Void}
+ */
+function assertVoid(node) {
   assertNode(node)
 
   nodeAssert.strictEqual('value' in node, false, 'void should not have `value`')
@@ -135,7 +244,12 @@ function empty(node) {
   )
 }
 
-// Assert `position` is a unist position.
+/**
+ * Assert `position` is a unist position.
+ *
+ * @param {Position} position
+ * @returns {asserts position is Position}
+ */
 function position(position) {
   if (position !== null && position !== undefined) {
     nodeAssert.ok(
@@ -148,27 +262,36 @@ function position(position) {
   }
 }
 
-// Assert `point` is a unist point.
-function point(point, name) {
+/**
+ * Assert `point` is a unist point.
+ *
+ * @param {Point} point
+ * @param {string} label
+ * @returns {asserts point is Point}
+ */
+function point(point, label) {
   if (point !== null && point !== undefined) {
-    nodeAssert.ok(point === Object(point), '`' + name + '` should be an object')
+    nodeAssert.ok(
+      point === Object(point),
+      '`' + label + '` should be an object'
+    )
 
     if (point.line !== null && point.line !== undefined) {
       nodeAssert.ok(
         'line' in point,
-        '`' + name + '` should have numeric `line`'
+        '`' + label + '` should have numeric `line`'
       )
-      nodeAssert.ok(point.line >= 1, '`' + name + '.line` should be gte `1`')
+      nodeAssert.ok(point.line >= 1, '`' + label + '.line` should be gte `1`')
     }
 
     if (point.column !== null && point.column !== undefined) {
       nodeAssert.ok(
         'column' in point,
-        '`' + name + '` should have numeric `column`'
+        '`' + label + '` should have numeric `column`'
       )
       nodeAssert.ok(
         point.column >= 1,
-        '`' + name + '.column` should be gte `1`'
+        '`' + label + '.column` should be gte `1`'
       )
     }
   }

index.test-d.ts

@@ -0,0 +1,18 @@
+import {expectType, expectNotType} from 'tsd'
+import {Node, Parent} from 'unist'
+import {assert, parent} from './index.js'
+
+var emptyNode = {type: 'a'}
+var literalNode = {type: 'b', value: 'c'}
+var parentNode = {type: 'd', children: [emptyNode, literalNode]}
+
+expectNotType<Node>(emptyNode)
+expectNotType<Node>(literalNode)
+expectNotType<Node>(parentNode)
+
+assert(emptyNode)
+expectType<Node>(emptyNode)
+
+expectNotType<Parent>(parentNode)
+parent(parentNode)
+expectType<Parent>(parentNode)

inspect.browser.js

@@ -1,3 +1,7 @@
+/**
+ * @param {unknown} value
+ * @returns {string}
+ */
 export function inspect(value) {
   return JSON.stringify(value)
 }

inspect.js

@@ -1,5 +1,9 @@
 import {inspect as utilInspect} from 'util'
 
+/**
+ * @param {unknown} value
+ * @returns {string}
+ */
 export function inspect(value) {
   return utilInspect(value, {colors: false})
 }