test: array.splice

Author: kaelzhang

src/array.js

@@ -131,18 +131,28 @@ const move_comments = (
 
 class CommentArray extends Array {
   // - deleteCount + items.length
-  splice (begin, deleteCount, ...items) {
-    const {length} = this
 
-    const ret = super.splice(begin, deleteCount, ...items)
+  // We should avoid `splice(begin, deleteCount, ...items)`,
+  // because `splice(0, undefined)` is not equivalent to `splice(0)`
+  splice (...args) {
+    const {length} = this
+    const ret = super.splice(...args)
 
-    // > If deleteCount is 0 or negative, no elements are removed.
-    // > In this case, you should specify at least one new element (see below).
-    if (deleteCount <= 0) {
+    // If no element removed, just skip moving comments.
+    // This is also used as argument type checking
+    if (!ret.length) {
       return ret
     }
 
-    if (deleteCount === UNDEFINED) {
+    // JavaScript syntax is silly
+    // eslint-disable-next-line prefer-const
+    let [begin, deleteCount, ...items] = args
+
+    if (begin < 0) {
+      begin += length
+    }
+
+    if (arguments.length === 1) {
       deleteCount = length - begin
     } else {
       deleteCount = Math.min(length - begin, deleteCount)

test/array.test.js

@@ -11,28 +11,56 @@ const a1 = `[
   2
 ]`
 
-const CASES = [
-  [
-    'splice',
-    a1,
-    array => array.splice(0, 1),
-    (t, ret, str) => {
-      t.deepEqual(ret, [0])
-      t.is(str, `[
+const a2 = `[
   // 1
   1,
   // 2
   2
-]`)
-    }
+]`
+
+const CASES = [
+  [
+    'splice(0, 1)',
+    a1,
+    array => array.splice(0, 1),
+    [0],
+    a2
+  ],
+  [
+    'splice(0)',
+    a1,
+    array => array.splice(0),
+    [0, 1, 2],
+    '[]'
+  ],
+  [
+    'splice(- 3, 1)',
+    a1,
+    array => array.splice(- 3, 1),
+    [0],
+    a2
+  ],
+  [
+    'invalid: splice(0, undefined)',
+    a1,
+    array => array.splice(0, undefined),
+    [],
+    a1
   ]
 ]
 
-CASES.forEach(([d, a, run, expect]) => {
+CASES.forEach(([d, a, run, e, s]) => {
   test(d, t => {
     const parsed = parse(a)
     const ret = run(parsed)
 
+    const expect = isFunction(e)
+      ? e
+      : (tt, r, str) => {
+        tt.deepEqual(r, e)
+        tt.is(str, s)
+      }
+
     expect(t, [...ret], stringify(parsed, null, 2), parsed, ret)
   })
 })