debugger: Relax implementation of validate_config to not run validation (#31785)

When we moved to schema-based debug configs, we've added validate_config
- a trait method
that is supposed to both validate the configuration and determine
whether it is a launch configuration
or an attach configuration.

The validation bit is a bit problematic though - we received reports on
Discords about
scenarios not starting up properly; it turned out that Javascript's
implementation was overly strict.
Thus, I got rid of any code that tries to validate the config - let's
let the debug adapter itself
decide whether it can digest the configuration or not. validate_config
is now left unimplemented for most
DebugAdapter implementations (except for PHP), because all adapters use
`request`: 'launch'/'attach' for that.
Let's leave the trait method in place though, as nothing guarantees this
to be true for all adapters.

cc @Anthony-Eid

Release Notes:

- debugger: Improved error messages when the debug scenario is not
valid.
- debugger: Fixed cases where valid configs were rejected.

crates/dap/src/adapters.rs

@@ -370,21 +370,19 @@ pub trait DebugAdapter: 'static + Send + Sync {
         None
     }
 
-    fn validate_config(
+    /// Extracts the kind (attach/launch) of debug configuration from the given JSON config.
+    /// This method should only return error when the kind cannot be determined for a given configuration;
+    /// in particular, it *should not* validate whether the request as a whole is valid, because that's best left to the debug adapter itself to decide.
+    fn request_kind(
         &self,
         config: &serde_json::Value,
     ) -> Result<StartDebuggingRequestArgumentsRequest> {
-        let map = config.as_object().context("Config isn't an object")?;
-
-        let request_variant = map
-            .get("request")
-            .and_then(|val| val.as_str())
-            .context("request argument is not found or invalid")?;
-
-        match request_variant {
-            "launch" => Ok(StartDebuggingRequestArgumentsRequest::Launch),
-            "attach" => Ok(StartDebuggingRequestArgumentsRequest::Attach),
-            _ => Err(anyhow!("request must be either 'launch' or 'attach'")),
+        match config.get("request") {
+            Some(val) if val == "launch" => Ok(StartDebuggingRequestArgumentsRequest::Launch),
+            Some(val) if val == "attach" => Ok(StartDebuggingRequestArgumentsRequest::Attach),
+            _ => Err(anyhow!(
+                "missing or invalid `request` field in config. Expected 'launch' or 'attach'"
+            )),
         }
     }
 
@@ -414,7 +412,7 @@ impl DebugAdapter for FakeAdapter {
         serde_json::Value::Null
     }
 
-    fn validate_config(
+    fn request_kind(
         &self,
         config: &serde_json::Value,
     ) -> Result<StartDebuggingRequestArgumentsRequest> {
@@ -459,7 +457,7 @@ impl DebugAdapter for FakeAdapter {
             envs: HashMap::default(),
             cwd: None,
             request_args: StartDebuggingRequestArguments {
-                request: self.validate_config(&task_definition.config)?,
+                request: self.request_kind(&task_definition.config)?,
                 configuration: task_definition.config.clone(),
             },
         })

crates/dap/src/dap.rs

@@ -52,7 +52,7 @@ pub fn send_telemetry(scenario: &DebugScenario, location: TelemetrySpawnLocation
         return;
     };
     let kind = adapter
-        .validate_config(&scenario.config)
+        .request_kind(&scenario.config)
         .ok()
         .map(serde_json::to_value)
         .and_then(Result::ok);