[lldb-dap] Provide declarationLocation for variables

TODO:

* Adjust comment on `CreateVariable` function with updated jsonschema as
  soon as the upstream changes were merged to DAP.

`declarationLocation` is about to become part of the upstream
debug-adapter-protocol. This is a draft implementation, to be finalized
and merged after the corresponding changes were merged into DAP.

Author: vogelsgesang

lldb/test/API/tools/lldb-dap/variables/TestDAP_variables.py

@@ -168,6 +168,10 @@ def do_test_scopes_variables_setVariable_evaluate(
                     "type": "int",
                     "value": "1",
                 },
+                "declarationLocation": {
+                    "equals": {"line": 12, "column": 14},
+                    "contains": {"path": ["lldb-dap", "variables", "main.cpp"]},
+                },
                 "$__lldb_extensions": {
                     "equals": {
                         "value": "1",

lldb/tools/lldb-dap/JSONUtils.cpp

@@ -614,9 +614,8 @@ CreateExceptionBreakpointFilter(const ExceptionBreakpoint &bp) {
 //     }
 //   }
 // }
-llvm::json::Value CreateSource(lldb::SBLineEntry &line_entry) {
+llvm::json::Value CreateSource(const lldb::SBFileSpec &file) {
   llvm::json::Object object;
-  lldb::SBFileSpec file = line_entry.GetFileSpec();
   if (file.IsValid()) {
     const char *name = file.GetFilename();
     if (name)
@@ -630,6 +629,10 @@ llvm::json::Value CreateSource(lldb::SBLineEntry &line_entry) {
   return llvm::json::Value(std::move(object));
 }
 
+llvm::json::Value CreateSource(const lldb::SBLineEntry &line_entry) {
+  return CreateSource(line_entry.GetFileSpec());
+}
+
 llvm::json::Value CreateSource(llvm::StringRef source_path) {
   llvm::json::Object source;
   llvm::StringRef name = llvm::sys::path::filename(source_path);
@@ -1253,6 +1256,17 @@ llvm::json::Value CreateVariable(lldb::SBValue v, int64_t variablesReference,
   else
     object.try_emplace("variablesReference", (int64_t)0);
 
+  if (lldb::SBDeclaration decl = v.GetDeclaration(); decl.IsValid()) {
+    llvm::json::Object decl_obj;
+    decl_obj.try_emplace("source", CreateSource(decl.GetFileSpec()));
+    if (int line = decl.GetLine())
+      decl_obj.try_emplace("line", line);
+    if (int column = decl.GetColumn())
+      decl_obj.try_emplace("column", column);
+
+    object.try_emplace("declarationLocation", std::move(decl_obj));
+  }
+
   object.try_emplace("$__lldb_extensions", desc.GetVariableExtensionsJSON());
   return llvm::json::Value(std::move(object));
 }

lldb/tools/lldb-dap/JSONUtils.h

@@ -282,16 +282,26 @@ llvm::json::Value CreateScope(const llvm::StringRef name,
                               int64_t variablesReference,
                               int64_t namedVariables, bool expensive);
 
+/// Create a "Source" JSON object as described in the debug adaptor definition.
+///
+/// \param[in] file
+///     The SBFileSpec to use when populating out the "Source" object
+///
+/// \return
+///     A "Source" JSON object that follows the formal JSON
+///     definition outlined by Microsoft.
+llvm::json::Value CreateSource(const lldb::SBFileSpec &file);
+
 /// Create a "Source" JSON object as described in the debug adaptor definition.
 ///
 /// \param[in] line_entry
 ///     The LLDB line table to use when populating out the "Source"
 ///     object
 ///
 /// \return
-///     A "Source" JSON object with that follows the formal JSON
+///     A "Source" JSON object that follows the formal JSON
 ///     definition outlined by Microsoft.
-llvm::json::Value CreateSource(lldb::SBLineEntry &line_entry);
+llvm::json::Value CreateSource(const lldb::SBLineEntry &line_entry);
 
 /// Create a "Source" object for a given source path.
 ///