[analysis_server] Support folding try/catch/finally blocks

Fixes Dart-Code/Dart-Code#5201

Change-Id: I1790d3aa624d80ad0233216ca650d497f31c632b
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/431281
Reviewed-by: Samuel Rawlins <[email protected]>
Commit-Queue: Brian Wilkerson <[email protected]>
Reviewed-by: Brian Wilkerson <[email protected]>

Author: DanTup

pkg/analysis_server/lib/src/computer/computer_folding.dart

@@ -31,8 +31,8 @@ class DartUnitFoldingComputer {
     //
     //    class Foo { [...] }
     //
-    // For if statements, they may have else/elseIfs which would result in long
-    // lines like:
+    // For if/try statements, they may have else/elseIfs which would result in
+    // long lines like:
     //
     //     if (cond) { [...] } else { [...] }
     //
@@ -523,6 +523,19 @@ class _DartUnitFoldingComputerVisitor extends RecursiveAstVisitor<void> {
     super.visitSwitchStatement(node);
   }
 
+  @override
+  void visitTryStatement(TryStatement node) {
+    _computer.addRegionForConditionalBlock(node.body);
+    for (var catchNode in node.catchClauses) {
+      _computer.addRegionForConditionalBlock(catchNode.body);
+    }
+    if (node.finallyBlock case var finallyNode?) {
+      _computer.addRegionForConditionalBlock(finallyNode);
+    }
+
+    super.visitTryStatement(node);
+  }
+
   @override
   void visitWhileStatement(WhileStatement node) {
     var body = node.body;

pkg/analysis_server/test/lsp/folding_test.dart

@@ -470,6 +470,67 @@ void f(int a) {
     }, requireAll: false);
   }
 
+  /// Even without lineFolding, try/catch/finally folding regions end
+  /// on the last statement of each block (matching if/else) to avoid long
+  /// lines when folded.
+  Future<void> test_tryCatchFinally() async {
+    var content = '''
+void f() {
+  try {/*[0*/
+    print('');
+    print('');/*0]*/
+  } on ArgumentError catch (_) {/*[1*/
+    print('');
+    print('');/*1]*/
+  } catch (e) {/*[2*/
+    print('');
+    print('');/*2]*/
+  } finally {/*[3*/
+    print('');
+    print('');/*3]*/
+  }
+}
+''';
+
+    await computeRanges(content);
+    expectRangesContain({
+      0: noFoldingKind,
+      1: noFoldingKind,
+      2: noFoldingKind,
+      3: noFoldingKind,
+    });
+  }
+
+  Future<void> test_tryCatchFinally_lineFoldingOnly() async {
+    lineFoldingOnly = true;
+
+    var content = '''
+void f() {
+  try {/*[0*/
+    print('');
+    print('');/*0]*/
+  } on ArgumentError catch (_) {/*[1*/
+    print('');
+    print('');/*1]*/
+  } catch (e) {/*[2*/
+    print('');
+    print('');/*2]*/
+  } finally {/*[3*/
+    print('');
+    print('');/*3]*/
+  }
+}
+''';
+
+    await computeRanges(content);
+    expectRangesContain({
+      0: noFoldingKind,
+      1: noFoldingKind,
+      2: noFoldingKind,
+      3: noFoldingKind,
+    });
+  }
+
   Future<void> test_whileLoop() async {
     var content = '''
 f(int i) {

pkg/analysis_server/test/src/computer/folding_computer_test.dart

@@ -1040,6 +1040,35 @@ void f() {}
     expectNoRegions();
   }
 
+  Future<void> test_tryCatchFinally() async {
+    var content = '''
+void f/*[0*/() {
+  try {/*[1*/
+    print('');
+    print('');/*1]*/
+  } on ArgumentError catch (_) {/*[2*/
+    print('');
+    print('');/*2]*/
+  } catch (e) {/*[3*/
+    print('');
+    print('');/*3]*/
+  } finally {/*[4*/
+    print('');
+    print('');/*4]*/
+  }
+}/*0]*/
+''';
+
+    await _computeRegions(content);
+    expectRegions({
+      0: FoldingKind.FUNCTION_BODY,
+      1: FoldingKind.BLOCK,
+      2: FoldingKind.BLOCK,
+      3: FoldingKind.BLOCK,
+      4: FoldingKind.BLOCK,
+    });
+  }
+
   Future<void> _computeRegions(String sourceContent) async {
     code = TestCode.parse(normalizeSource(sourceContent));
     var file = newFile(sourcePath, code.code);