[lldb] [llvm] [lldb-dap] Add support for data breakpoint. (PR #81541)

[Walter Erquinigo via llvm-commits]

================
@@ -2591,6 +2594,248 @@ void request_setFunctionBreakpoints(const llvm::json::Object &request) {
   g_dap.SendJSON(llvm::json::Value(std::move(response)));
 }
 
+// "DataBreakpointInfoRequest": {
+//   "allOf": [ { "$ref": "#/definitions/Request" }, {
+//     "type": "object",
+//     "description": "Obtains information on a possible data breakpoint that
+//     could be set on an expression or variable.\nClients should only call this
+//     request if the corresponding capability `supportsDataBreakpoints` is
+//     true.", "properties": {
+//       "command": {
+//         "type": "string",
+//         "enum": [ "dataBreakpointInfo" ]
+//       },
+//       "arguments": {
+//         "$ref": "#/definitions/DataBreakpointInfoArguments"
+//       }
+//     },
+//     "required": [ "command", "arguments"  ]
+//   }]
+// },
+// "DataBreakpointInfoArguments": {
+//   "type": "object",
+//   "description": "Arguments for `dataBreakpointInfo` request.",
+//   "properties": {
+//     "variablesReference": {
+//       "type": "integer",
+//       "description": "Reference to the variable container if the data
+//       breakpoint is requested for a child of the container. The
+//       `variablesReference` must have been obtained in the current suspended
+//       state. See 'Lifetime of Object References' in the Overview section for
+//       details."
+//     },
+//     "name": {
+//       "type": "string",
+//       "description": "The name of the variable's child to obtain data
+//       breakpoint information for.\nIf `variablesReference` isn't specified,
+//       this can be an expression."
+//     },
+//     "frameId": {
+//       "type": "integer",
+//       "description": "When `name` is an expression, evaluate it in the scope
+//       of this stack frame. If not specified, the expression is evaluated in
+//       the global scope. When `variablesReference` is specified, this property
+//       has no effect."
+//     }
+//   },
+//   "required": [ "name" ]
+// },
+// "DataBreakpointInfoResponse": {
+//   "allOf": [ { "$ref": "#/definitions/Response" }, {
+//     "type": "object",
+//     "description": "Response to `dataBreakpointInfo` request.",
+//     "properties": {
+//       "body": {
+//         "type": "object",
+//         "properties": {
+//           "dataId": {
+//             "type": [ "string", "null" ],
+//             "description": "An identifier for the data on which a data
+//             breakpoint can be registered with the `setDataBreakpoints`
+//             request or null if no data breakpoint is available. If a
+//             `variablesReference` or `frameId` is passed, the `dataId` is
+//             valid in the current suspended state, otherwise it's valid
+//             indefinitely. See 'Lifetime of Object References' in the Overview
+//             section for details. Breakpoints set using the `dataId` in the
+//             `setDataBreakpoints` request may outlive the lifetime of the
+//             associated `dataId`."
+//           },
+//           "description": {
+//             "type": "string",
+//             "description": "UI string that describes on what data the
+//             breakpoint is set on or why a data breakpoint is not available."
+//           },
+//           "accessTypes": {
+//             "type": "array",
+//             "items": {
+//               "$ref": "#/definitions/DataBreakpointAccessType"
+//             },
+//             "description": "Attribute lists the available access types for a
+//             potential data breakpoint. A UI client could surface this
+//             information."
+//           },
+//           "canPersist": {
+//             "type": "boolean",
+//             "description": "Attribute indicates that a potential data
+//             breakpoint could be persisted across sessions."
+//           }
+//         },
+//         "required": [ "dataId", "description" ]
+//       }
+//     },
+//     "required": [ "body" ]
+//   }]
+// }
+void request_dataBreakpointInfo(const llvm::json::Object &request) {
+  llvm::json::Object response;
+  FillResponse(request, response);
+  llvm::json::Object body;
+  lldb::SBError error;
+  llvm::json::Array accessTypes{"read", "write", "readWrite"};
+  const auto *arguments = request.getObject("arguments");
+  const auto variablesReference =
+      GetUnsigned(arguments, "variablesReference", 0);
----------------
walter-erquinigo wrote:

it'd be better to use a non-zero default value, which might collide with an actual variable ref id

https://github.com/llvm/llvm-project/pull/81541