gdb/dap - Add CompletionsRequest

Use GDB/MI command "-complete" to implement.

Co-authored-by: Simon Farre <simon.farre.cx@gmail.com>
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=31140
Approved-By: Tom Tromey <tom@tromey.com>
Reviewed-By: Eli Zaretskii <eliz@gnu.org>

gdb/NEWS

@@ -3,6 +3,10 @@
 
 *** Changes since GDB 16
 
+* Debugger Adapter Protocol changes
+
+  ** GDB now supports the "completions" request.
+
 * "set style" commands now supports numeric format for basic colors
   from 0 to 255 and #RRGGBB format for TrueColor.
 

gdb/data-directory/Makefile.in

@@ -97,6 +97,7 @@ PYTHON_FILE_LIST = \
 	gdb/command/xmethods.py \
 	gdb/dap/breakpoint.py \
 	gdb/dap/bt.py \
+	gdb/dap/completions.py \
 	gdb/dap/disassemble.py \
 	gdb/dap/evaluate.py \
 	gdb/dap/events.py \

gdb/python/lib/gdb/dap/__init__.py

@@ -26,6 +26,7 @@ from . import startup
 # server object.  "F401" is the flake8 "imported but unused" code.
 from . import breakpoint  # noqa: F401
 from . import bt  # noqa: F401
+from . import completions  # noqa: F401
 from . import disassemble  # noqa: F401
 from . import evaluate  # noqa: F401
 from . import launch  # noqa: F401

gdb/python/lib/gdb/dap/completions.py

@@ -0,0 +1,60 @@
+# Copyright 2025 Free Software Foundation, Inc.
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+from typing import Optional
+
+from .frames import select_frame
+from .server import capability, import_column, import_line, request
+from .startup import exec_mi_and_log
+
+
+@request("completions")
+@capability("supportsCompletionsRequest")
+@capability("completionTriggerCharacters", [" ", "."])
+def completions(
+    *,
+    frameId: Optional[int] = None,
+    text: str,
+    column: int,
+    line: Optional[int] = None,
+    **extra,
+):
+    if frameId is not None:
+        select_frame(frameId)
+
+    column = import_column(column)
+    if line is None:
+        line = 1
+    else:
+        line = import_line(line)
+    text = text.splitlines()[line - 1]
+    text = text[: column - 1]
+    mi_result = exec_mi_and_log("-complete", text)
+    result = []
+    completion = None
+    if "completion" in mi_result:
+        completion = mi_result["completion"]
+        result.append({"label": completion, "length": len(completion)})
+    # If `-complete' finds one match then `completion' and `matches'
+    # will contain the same one match.
+    if (
+        completion is not None
+        and len(mi_result["matches"]) == 1
+        and completion == mi_result["matches"][0]
+    ):
+        return {"targets": result}
+    for match in mi_result["matches"]:
+        result.append({"label": match, "length": len(match)})
+    return {"targets": result}

gdb/python/lib/gdb/dap/server.py

@@ -49,6 +49,7 @@ _server = None
 # This is set by the initialize request and is used when rewriting
 # line numbers.
 _lines_start_at_1 = False
+_columns_start_at_1 = False
 
 
 class DeferredRequest:
@@ -593,6 +594,8 @@ def initialize(**args):
     _server.send_event_later("initialized")
     global _lines_start_at_1
     _lines_start_at_1 = client_bool_capability("linesStartAt1", True)
+    global _columns_start_at_1
+    _columns_start_at_1 = client_bool_capability("columnsStartAt1", True)
     return _capabilities.copy()
 
 
@@ -698,7 +701,7 @@ def send_gdb_with_response(fn):
     return val
 
 
-def export_line(line):
+def export_line(line: int) -> int:
     """Rewrite LINE according to client capability.
     This applies the linesStartAt1 capability as needed,
     when sending a line number from gdb to the client."""
@@ -710,7 +713,7 @@ def export_line(line):
     return line
 
 
-def import_line(line):
+def import_line(line: int) -> int:
     """Rewrite LINE according to client capability.
     This applies the linesStartAt1 capability as needed,
     when the client sends a line number to gdb."""
@@ -720,3 +723,17 @@ def import_line(line):
         # the client starts at 0.
         line = line + 1
     return line
+
+
+def export_column(column: int) -> int:
+    """Rewrite COLUMN according to client capability.
+    This applies the columnsStartAt1 capability as needed,
+    when sending a column number from gdb to the client."""
+    return column if _columns_start_at_1 else column - 1
+
+
+def import_column(column: int) -> int:
+    """Rewrite COLUMN according to client capability.
+    This applies the columnsStartAt1 capability as needed,
+    when the client sends a column number to gdb."""
+    return column if _columns_start_at_1 else column + 1