feat(new-refactoring): Add Split Declaration and Initialization refactoring code action! Activation range is const or let keyword.

fixes #108
also add comparing refactor extensions docs

Author: zardoy

REFACTOR-EXTENSIONS-COMPARING.MD

@@ -0,0 +1,10 @@
+# VS CODE Refactor Extensions Comparing
+
+All of these extensions are free to use and can be used offline.
+
+| Extension                                                                                                       | Good number of actions | Actions quality                                                            | Performance Optimizations                           |
+| --------------------------------------------------------------------------------------------------------------- | ---------------------- | -------------------------------------------------------------------------- | --------------------------------------------------- |
+| [JS Refactor :: JS CodeFormer](https://marketplace.visualstudio.com/items?itemName=cmstead.jsrefactor)          | ✅                      | ❌ (Extension abandoned)                                                    | ?                                                   |
+| [Abracadabra, refactor this!](https://marketplace.visualstudio.com/items?itemName=nicoespeon.abracadabra)       | ✅                      | ❌ Sometimes buggy, doesn't work with syntax errors, no TS types auto-infer | ❌ (Uses extension host, slow downs other extension) |
+| [JS Refactoring Assistant (P42)](https://marketplace.visualstudio.com/items?itemName=p42ai.refactor)            | ✅                      | JS - ✅, TS - ❌ (You need to write types yourself)                          | ✅ (Dedicated language server)                       |
+| [TypeScript Essential Plugins](https://marketplace.visualstudio.com/items?itemName=zardoy.ts-essential-plugins) | ❌                      | ✅? (Auto infers types, but missing a lot of tests)                         | ✅ (Best possible, reuses TS language server)        |

typescript/src/codeActions/custom/splitDeclarationAndInitialization.ts

@@ -0,0 +1,47 @@
+import { getChangesTracker, getIndentFromPos } from '../../utils'
+import { CodeAction } from '../getCodeActions'
+
+export default {
+    name: 'Split Declaration and Initialization',
+    id: 'splitDeclarationAndInitialization',
+    kind: 'refactor.rewrite.split-declaration-and-initialization',
+    tryToApply(sourceFile, position, range, node, formatOptions, languageService, languageServiceHost) {
+        if (range || !node) return
+        if (!ts.isVariableDeclarationList(node) || node.declarations.length !== 1) return
+        const declaration = node.declarations[0]!
+        if (position > declaration.pos || !declaration.initializer || !ts.isIdentifier(declaration.name)) return
+        if (!formatOptions) return true
+        const typeChecker = languageService.getProgram()!.getTypeChecker()!
+        let typeNode = declaration.type
+        if (!typeNode) {
+            let type = typeChecker.getTypeAtLocation(declaration)
+            if (type.isLiteral()) {
+                type = typeChecker.getBaseTypeOfLiteralType(type)
+            }
+            typeNode = typeChecker.typeToTypeNode(type, node.parent, ts.NodeBuilderFlags.NoTruncation)
+        }
+        const changesTracker = getChangesTracker(formatOptions)
+        const { factory } = ts
+        const nodeStart = node.pos + node.getLeadingTriviaWidth()
+        const varName = declaration.name.text
+        changesTracker.insertNodeAt(
+            sourceFile,
+            nodeStart,
+            factory.createVariableDeclarationList(
+                [factory.createVariableDeclaration(factory.createIdentifier(varName), undefined, typeNode)],
+                ts.NodeFlags.Let,
+            ),
+        )
+        changesTracker.replaceNode(
+            sourceFile,
+            node,
+            factory.createBinaryExpression(factory.createIdentifier(varName), factory.createToken(ts.SyntaxKind.EqualsToken), declaration.initializer),
+            {
+                prefix: `\n${getIndentFromPos(ts, sourceFile, position)}`,
+                suffix: '\n',
+                leadingTriviaOption: /*Ignore all*/ 0,
+            },
+        )
+        return changesTracker.getChanges()[0]?.textChanges as ts.TextChange[]
+    },
+} satisfies CodeAction

typescript/src/codeActions/getCodeActions.ts

@@ -2,6 +2,7 @@ import { compact } from '@zardoy/utils'
 import { findChildContainingPosition } from '../utils'
 import objectSwapKeysAndValues from './custom/objectSwapKeysAndValues'
 import changeStringReplaceToRegex from './custom/changeStringReplaceToRegex'
+import splitDeclarationAndInitialization from './custom/splitDeclarationAndInitialization'
 
 type SimplifiedRefactorInfo =
     | {
@@ -30,7 +31,7 @@ export type CodeAction = {
     tryToApply: ApplyCodeAction
 }
 
-const codeActions: CodeAction[] = [/* toggleBraces */ objectSwapKeysAndValues, changeStringReplaceToRegex]
+const codeActions: CodeAction[] = [/* toggleBraces */ objectSwapKeysAndValues, changeStringReplaceToRegex, splitDeclarationAndInitialization]
 
 export const REFACTORS_CATEGORY = 'essential-refactors'