Add hidden feature to not add keys

Solid currently sees a third argument, even when `undefined`, as the children.
Which results in actual children being ignored.

I’m planning to open a PR to solve that.
But for now, here’s a little workaround.

Author: wooorm

Diff for: lib/index.js

@@ -21,7 +21,7 @@
  *   Element type: `Fragment` symbol, tag name (`string`), component.
  * @param {Props} props
  *   Element props, `children`, and maybe `node`.
- * @param {string | undefined} key
+ * @param {string | undefined} [key]
  *   Dynamicly generated key to use.
  * @returns {JSX.Element}
  *   An element from your framework.
@@ -101,6 +101,8 @@
  *   File path.
  * @property {Partial<Components>} components
  *   Components to swap.
+ * @property {boolean} passKeys
+ *   Generate keys to optimize frameworks that support them.
  * @property {boolean} passNode
  *   Pass `node` to components.
  * @property {ElementAttributeNameCase} elementAttributeNameCase
@@ -126,6 +128,10 @@
  *
  *   Passed in source info to `jsxDEV` when using the automatic runtime with
  *   `development: true`.
+ * @property {boolean | null | undefined} [passKeys=true]
+ *   Generate keys to optimize frameworks that support them.
+ *
+ *   > 👉 **Note**: Solid currently fails if keys are passed.
  * @property {boolean | null | undefined} [passNode=false]
  *   Pass the hast element node to components.
  * @property {ElementAttributeNameCase | null | undefined} [elementAttributeNameCase='react']
@@ -205,6 +211,9 @@ import {whitespace} from 'hast-util-whitespace'
 
 const own = {}.hasOwnProperty
 
+/** @type {Map<string, number>} */
+const emptyMap = new Map()
+
 const cap = /[A-Z]/g
 const dashSomething = /-([a-z])/g
 
@@ -266,6 +275,7 @@ export function toJsxRuntime(tree, options) {
   const state = {
     Fragment: options.Fragment,
     schema: options.space === 'svg' ? svg : html,
+    passKeys: options.passKeys !== false,
     passNode: options.passNode || false,
     elementAttributeNameCase: options.elementAttributeNameCase || 'react',
     stylePropertyNameCase: options.stylePropertyNameCase || 'dom',
@@ -367,7 +377,7 @@ function productionCreate(_, jsx, jsxs) {
   function create(_, type, props, key) {
     const isStaticChildren = props.children ? props.children.length > 1 : false
     const fn = isStaticChildren ? jsxs : jsx
-    return fn(type, props, key)
+    return key ? fn(type, props, key) : fn(type, props)
   }
 }
 
@@ -415,14 +425,16 @@ function createChildren(state, node) {
   const children = []
   let index = -1
   /** @type {Map<string, number>} */
-  const countsByTagName = new Map()
+  // Note: test this when Solid doesn’t want to merge my upcoming PR.
+  /* c8 ignore next */
+  const countsByTagName = state.passKeys ? new Map() : emptyMap
 
   while (++index < node.children.length) {
     const child = node.children[index]
     /** @type {string | undefined} */
     let key
 
-    if (child.type === 'element') {
+    if (state.passKeys && child.type === 'element') {
       const count = countsByTagName.get(child.tagName) || 0
       key = child.tagName + '-' + count
       countsByTagName.set(child.tagName, count + 1)