Support name-based destructuring declarations (#630)

Summary:
- Preserve square-bracket destructuring delimiters instead of always emitting parentheses.
- Format name-based destructuring entries with renames such as `x = b`.
- Add regression coverage for bracket destructuring and rename spacing.

Fixes #629

## Tests

- `./gradlew :ktfmt:test --tests "com.facebook.ktfmt.format.FormatterTest.handle name based destructuring declaration" --no-daemon --console=plain --stacktrace`
- `./gradlew :ktfmt:test --tests "com.facebook.ktfmt.format.FormatterTest" --no-daemon --console=plain --stacktrace`
- `./gradlew :ktfmt:build --no-daemon --console=plain --stacktrace`

Note: I also tried `./gradlew build --no-daemon --console=plain --stacktrace`; the local run reached ktfmt checks, then failed in unrelated `:lambda:test` dependency resolution because local Maven is missing `io.netty:netty-transport-native-epoll:4.1.42.Final:linux-x86_64`.

Pull Request resolved: #630

Reviewed By: cortinico

Differential Revision: D108969079

Pulled By: hick209

fbshipit-source-id: 2a30f0fac7ab7db5b95ddb2ffaa0ce9e9cb8c9a4

Author: goutamadwant

CHANGELOG.md

@@ -17,6 +17,10 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/).
 * Reduced overall number of allocations to improve formatting performance (~6-7%) (https://github.com/facebook/ktfmt/pull/620)
 * Reuse results of `Parser.parse` (https://github.com/facebook/ktfmt/pull/622)
 
+### Fixed
+
+* Support name-based destructuring declarations. (https://github.com/facebook/ktfmt/issues/629)
+
 ## [0.63]
 
 ### Added

core/src/main/java/com/facebook/ktfmt/format/KotlinInputAstVisitor.kt

@@ -2248,7 +2248,7 @@ class KotlinInputAstVisitor(
     builder.token("]")
   }
 
-  /** Example `val (a, b: Int) = Pair(1, 2)` */
+  /** Example `val (a, b: Int) = Pair(1, 2)` or `val [a, b] = Pair(1, 2)` */
   override fun visitDestructuringDeclaration(destructuringDeclaration: KtDestructuringDeclaration) {
     builder.sync(destructuringDeclaration)
     val valOrVarKeyword = destructuringDeclaration.valOrVarKeyword
@@ -2257,8 +2257,10 @@ class KotlinInputAstVisitor(
       builder.space()
     }
     val hasTrailingComma = destructuringDeclaration.trailingComma != null
+    val openingDelimiter = destructuringDeclaration.lPar?.text ?: "("
+    val closingDelimiter = destructuringDeclaration.rPar?.text ?: ")"
     builder.block(ZERO) {
-      builder.token("(")
+      builder.token(openingDelimiter)
       builder.breakOp(Doc.FillMode.UNIFIED, "", expressionBreakIndent)
       builder.block(expressionBreakIndent) {
         visitEachCommaSeparated(
@@ -2268,7 +2270,7 @@ class KotlinInputAstVisitor(
         )
       }
     }
-    builder.token(")")
+    builder.token(closingDelimiter)
     val initializer = destructuringDeclaration.initializer
     if (initializer != null) {
       builder.space()
@@ -2282,13 +2284,13 @@ class KotlinInputAstVisitor(
     }
   }
 
-  /** Example `a: String` which is part of `(a: String, b: String)` */
+  /** Example `a: String` or `x = a` which is part of `(a: String, x = a)` */
   override fun visitDestructuringDeclarationEntry(
       multiDeclarationEntry: KtDestructuringDeclarationEntry
   ) {
     builder.sync(multiDeclarationEntry)
     declareOne(
-        initializer = null,
+        initializer = multiDeclarationEntry.initializer,
         kind = DeclarationKind.PARAMETER,
         modifiers = multiDeclarationEntry.modifierList,
         name = multiDeclarationEntry.nameIdentifier?.text ?: fail(),

core/src/test/java/com/facebook/ktfmt/format/FormatterTest.kt

@@ -3073,6 +3073,30 @@ class FormatterTest {
           deduceMaxWidth = true,
       )
 
+  @Test
+  fun `handle name based destructuring declaration`() {
+    if (KotlinVersion.CURRENT < KotlinVersion(2, 3)) return
+
+    assertThatFormatting(
+            """
+            |fun f(d: D) {
+            |  val [a, b         ] = d
+            |  val (a, x = b         ) = d
+            |}
+            |"""
+                .trimMargin()
+        )
+        .isEqualTo(
+            """
+            |fun f(d: D) {
+            |  val [a, b] = d
+            |  val (a, x = b) = d
+            |}
+            |"""
+                .trimMargin()
+        )
+  }
+
   @Test
   fun `chains with derferences and array indexing`() =
       assertFormatted(