Add 'program' to DAP 'attach' request

In many cases, it's not possible for gdb to discover the executable
when a DAP 'attach' request is used.  This patch lets the IDE supply
this information.

Reviewed-By: Eli Zaretskii <eliz@gnu.org>

gdb/python/lib/gdb/dap/launch.py

@@ -28,6 +28,11 @@ from .startup import exec_and_log
 _program = None
 
 
+# True if the program was attached, False otherwise.  This should only
+# be accessed from the gdb thread.
+_attach = False
+
+
 # Any parameters here are necessarily extensions -- DAP requires this
 # from implementations.  Any additions or changes here should be
 # documented in the gdb manual.
@@ -43,6 +48,8 @@ def launch(
 ):
     global _program
     _program = program
+    global _attach
+    _attach = False
     if cwd is not None:
         exec_and_log("cd " + cwd)
     if program is not None:
@@ -60,10 +67,20 @@ def launch(
 
 
 @request("attach")
-def attach(*, pid: Optional[int] = None, target: Optional[str] = None, **args):
+def attach(
+    *,
+    program: Optional[str] = None,
+    pid: Optional[int] = None,
+    target: Optional[str] = None,
+    **args,
+):
     # Ensure configurationDone does not try to run.
+    global _attach
+    _attach = True
     global _program
-    _program = None
+    _program = program
+    if program is not None:
+        exec_and_log("file " + program)
     if pid is not None:
         cmd = "attach " + str(pid)
     elif target is not None:
@@ -77,7 +94,7 @@ def attach(*, pid: Optional[int] = None, target: Optional[str] = None, **args):
 @capability("supportsConfigurationDoneRequest")
 @request("configurationDone", response=False)
 def config_done(**args):
-    global _program
-    if _program is not None:
+    global _attach
+    if not _attach:
         expect_process("process")
         exec_and_expect_stop("run")