[lldb-dap] Add `--no-lldbinit` as a CLI flag (#156131)

TLDR
----------
This PR adds `--no-lldbinit` as a new CLI flag to the `lldb-dap`

Motivation
-----------
Rcently Users reported being unable to control `.lldbinit` file sourcing
when debugging through VS Code.
https://github.com/llvm/llvm-project/issues/155802.
VS Code extensions cannot easily inject custom parameters into the DAP
initialize request. Adding `--no-lldbinit` as a CLI flag solves this
problem by allowing the decision to skip `.lldbinit` files to be made at
debugger startup, before any initialization requests are processed.
VS Code extensions can control this behavior by specifying the flag
through `debugAdapterArgs` or similar mechanisms in launch
configurations.

```
{
  "type": <extension-type>,
  "request": "launch", 
  "name": "Debug with --no-lldbinit",
  "program": "${workspaceFolder}/your-program",
  "debugAdapterArgs": ["--no-lldbinit"]
}
```
Summary
----------
This PR introduces a new command-line flag `--no-lldbinit` (with alias
`-x`) to `lldb-dap`. The flag prevents automatic parsing of `.lldbinit`
files during debugger initialization, giving users control over whether
their LLDB initialization scripts are loaded.

### Key Changes:

1. **CLI Option Definition** (`Options.td`): Added the `--no-lldbinit`
flag with `-x` alias
2. **Core Implementation** (`DAP.cpp`): Added support for storing and
using the no-lldbinit flag
3. **Initialization Handler** (`InitializeRequestHandler.cpp`): Modified
to respect the flag during debugger initialization
4. **Main Tool** (`lldb-dap.cpp`): Added argument parsing for the new
flag
5. **Test Infrastructure** (`dap_server.py & lldbdap_testcase.py`):
Enhanced test framework to support additional arguments

Test Plan
---------

### New Test Coverage (`TestDAP_launch.py`)

**Test Method:** `test_no_lldbinit_flag()`

**Test Strategy:**

1. **Setup**: Creates a temporary `.lldbinit` file with specific
settings that would normally be loaded
2.  **Execution**: Launches lldb-dap with the `--no-lldbinit` flag
3. **Verification**: Confirms that the settings from `.lldbinit` are NOT
applied, proving the flag works correctly

**Test Environment:**

*   Uses a temporary home directory with a custom `.lldbinit` file
* Sets specific LLDB settings (`stop-disassembly-display never`,
`target.x86-disassembly-flavor intel`)
* Launches debug adapter with `--no-lldbinit` flag via `additional_args`
parameter

**Validation Approach:**

* Executes `settings show stop-disassembly-display` command during
initialization
* Verifies the output does NOT contain "never" (which would indicate
`.lldbinit` was sourced)
*   Confirms that initialization commands are still executed properly

### Testing Infrastructure Enhancements

**File Modifications:**

* `dap_server.py`: Enhanced to accept `additional_args` parameter for
passing extra CLI flags
* `lldbdap_testcase.py`: Updated `build_and_create_debug_adapter()`
method to support additional arguments and environment variables

### Unit Test Integration

**Unit Test Updates** (`DAPTest.cpp`):

* Added initialization of the new flag in test setup to ensure
consistent test behavior

**Test Run**
<img width="1759" height="1373" alt="Screenshot 2025-08-29 at 5 56
18 PM"
src="https://github.com/user-attachments/assets/769b319a-5009-4ade-aff8-c5f548b38123"
/>

---------

Co-authored-by: Piyush Jaiswal <piyushjais@meta.com>

2 files changed, 14 insertions, 2 deletions

diff --git a/lldb/packages/Python/lldbsuite/test/tools/lldb-dap/dap_server.py b/lldb/packages/Python/lldbsuite/test/tools/lldb-dap/dap_server.py
index 0608ac3..66aa070 100644
--- a/lldb/packages/Python/lldbsuite/test/tools/lldb-dap/dap_server.py
+++ b/lldb/packages/Python/lldbsuite/test/tools/lldb-dap/dap_server.py
@@ -1490,12 +1490,17 @@ class DebugAdapterServer(DebugCommunication):
         init_commands: list[str] = [],
         log_file: Optional[TextIO] = None,
         env: Optional[dict[str, str]] = None,
+        additional_args: list[str] = [],
     ):
         self.process = None
         self.connection = None
         if executable is not None:
             process, connection = DebugAdapterServer.launch(
-                executable=executable, connection=connection, env=env, log_file=log_file
+                executable=executable,
+                connection=connection,
+                env=env,
+                log_file=log_file,
+                additional_args=additional_args,
             )
             self.process = process
             self.connection = connection
@@ -1528,6 +1533,7 @@ class DebugAdapterServer(DebugCommunication):
         env: Optional[dict[str, str]] = None,
         log_file: Optional[TextIO] = None,
         connection: Optional[str] = None,
+        additional_args: list[str] = [],
     ) -> tuple[subprocess.Popen, Optional[str]]:
         adapter_env = os.environ.copy()
         if env is not None:
@@ -1537,6 +1543,9 @@ class DebugAdapterServer(DebugCommunication):
             adapter_env["LLDBDAP_LOG"] = log_file
         args = [executable]
 
+        # Add additional arguments first (like --no-lldbinit)
+        args.extend(additional_args)
+
         if connection is not None:
             args.append("--connection")
             args.append(connection)
diff --git a/lldb/packages/Python/lldbsuite/test/tools/lldb-dap/lldbdap_testcase.py b/lldb/packages/Python/lldbsuite/test/tools/lldb-dap/lldbdap_testcase.py
index b28a787..fffd4c2 100644
--- a/lldb/packages/Python/lldbsuite/test/tools/lldb-dap/lldbdap_testcase.py
+++ b/lldb/packages/Python/lldbsuite/test/tools/lldb-dap/lldbdap_testcase.py
@@ -21,6 +21,7 @@ class DAPTestCaseBase(TestBase):
         self,
         lldbDAPEnv: Optional[dict[str, str]] = None,
         connection: Optional[str] = None,
+        additional_args: Optional[list[str]] = None,
     ):
         """Create the Visual Studio Code debug adapter"""
         self.assertTrue(
@@ -33,15 +34,17 @@ class DAPTestCaseBase(TestBase):
             init_commands=self.setUpCommands(),
             log_file=log_file_path,
             env=lldbDAPEnv,
+            additional_args=additional_args or [],
         )
 
     def build_and_create_debug_adapter(
         self,
         lldbDAPEnv: Optional[dict[str, str]] = None,
         dictionary: Optional[dict] = None,
+        additional_args: Optional[list[str]] = None,
     ):
         self.build(dictionary=dictionary)
-        self.create_debug_adapter(lldbDAPEnv)
+        self.create_debug_adapter(lldbDAPEnv, additional_args=additional_args)
 
     def build_and_create_debug_adapter_for_attach(self):
         """Variant of build_and_create_debug_adapter that builds a uniquely