StatementSwitchToExpressionSwitch: for "assignment switch" and "direct conversion" transformations, retain comments appearing in the switch block before the first case

PiperOrigin-RevId: 696903291

Author: markhbrady

core/src/main/java/com/google/errorprone/bugpatterns/StatementSwitchToExpressionSwitch.java

@@ -544,7 +544,12 @@ private static SuggestedFix convertDirectlyToExpressionSwitch(
       String transformedBlockSource = transformBlock(caseTree, state, filteredStatements);
 
       if (firstCaseInGroup) {
-        groupedCaseCommentsAccumulator = new StringBuilder();
+        groupedCaseCommentsAccumulator =
+            new StringBuilder(
+                caseIndex == 0
+                    ? extractCommentsBeforeFirstCase(switchTree, allSwitchComments).orElse("")
+                    : "");
+
         replacementCodeBuilder.append("\n  ");
         if (!isDefaultCase) {
           replacementCodeBuilder.append("case ");
@@ -663,10 +668,10 @@ private static SuggestedFix convertToReturnSwitch(
 
       if (firstCaseInGroup) {
         groupedCaseCommentsAccumulator =
-            caseIndex == 0
-                ? new StringBuilder(
-                    extractCommentsBeforeFirstCase(switchTree, allSwitchComments).orElse(""))
-                : new StringBuilder();
+            new StringBuilder(
+                caseIndex == 0
+                    ? extractCommentsBeforeFirstCase(switchTree, allSwitchComments).orElse("")
+                    : "");
 
         replacementCodeBuilder.append("\n  ");
         if (!isDefaultCase) {
@@ -831,7 +836,12 @@ private static SuggestedFix convertToAssignmentSwitch(
           transformAssignOrThrowBlock(caseTree, state, filteredStatements);
 
       if (firstCaseInGroup) {
-        groupedCaseCommentsAccumulator = new StringBuilder();
+        groupedCaseCommentsAccumulator =
+            new StringBuilder(
+                caseIndex == 0
+                    ? extractCommentsBeforeFirstCase(switchTree, allSwitchComments).orElse("")
+                    : "");
+
         replacementCodeBuilder.append("\n  ");
         if (!isDefaultCase) {
           replacementCodeBuilder.append("case ");

core/src/test/java/com/google/errorprone/bugpatterns/StatementSwitchToExpressionSwitchTest.java

@@ -154,6 +154,7 @@ public Test(int foo) {}
               public void foo(Side side) {
                 // BUG: Diagnostic contains: [StatementSwitchToExpressionSwitch]
                 switch (side) {
+                  // Comment before first case
                   case OBVERSE:
                     // Explanatory comment
                     System.out.println("this block cannot complete normally");
@@ -185,6 +186,7 @@ public Test(int foo) {}
 
               public void foo(Side side) {
                 switch (side) {
+                  // Comment before first case
                   case OBVERSE:
                     // Explanatory comment
                     System.out.println("this block cannot complete normally");
@@ -211,6 +213,7 @@ public Test(int foo) {}
               public void foo(Side side) {
                 switch (side) {
                   case OBVERSE -> {
+                    // Comment before first case
                     // Explanatory comment
                     System.out.println("this block cannot complete normally");
                     {
@@ -3304,6 +3307,7 @@ public Test(int foo) {
               public int foo(Side side) {
                 // BUG: Diagnostic contains: [StatementSwitchToExpressionSwitch]
                 switch (side) {
+                  /* Comment before first case */
                   case /* LHS comment */ HEART:
                     // Inline comment
                     x <<= 2;
@@ -3347,6 +3351,7 @@ public Test(int foo) {
 
               public int foo(Side side) {
                 switch (side) {
+                  /* Comment before first case */
                   case /* LHS comment */ HEART:
                     // Inline comment
                     this.x <<= 2;
@@ -3384,6 +3389,7 @@ public int foo(Side side) {
                 this.x <<=
                     switch (side) {
                       case HEART ->
+                          /* Comment before first case */
                           /* LHS comment */
                           // Inline comment
                           2;