Allow tracing bindings, event handlers etc. with fish_trace=all

Might have helped with cases like #12209 where an event handler stomps
user preferences.

CHANGELOG.rst

@@ -33,6 +33,7 @@ Scripting improvements
 ----------------------
 - New :ref:`status language <status-language>` commands allow showing and modifying language settings for fish messages without having to modify environment variables.
 - When using a noninteractive fish instance to compute completions, ``commandline --cursor`` no works as expected instead of throwing an error (:issue:`11993`).
+- :envvar:`fish_trace` can now be set to ``all`` to also trace execution of key bindings, event handlers as well as prompt and title functions.
 
 Interactive improvements
 ------------------------

doc_src/language.rst

@@ -1628,6 +1628,7 @@ You can change the settings of fish by changing the values of certain variables.
    if set and not empty, will cause fish to print commands before they execute, similar to ``set -x`` in bash.
    The trace is printed to the path given by the `--debug-output` option to fish or the :envvar:`FISH_DEBUG_OUTPUT` variable.
    It goes to stderr by default.
+   Set it to ``all`` to also trace execution of key bindings, event handlers as well as prompt and title functions.
 
 .. envvar:: FISH_DEBUG
 

src/env/var.rs

@@ -164,15 +164,6 @@ pub fn as_string(&self) -> WString {
         join_strings(&self.values, self.get_delimiter())
     }
 
-    /// Copies the variable's values into an existing list, avoiding reallocation if possible.
-    pub fn to_list(&self, out: &mut Vec<WString>) {
-        // Try to avoid reallocation as much as possible.
-        out.resize(self.values.len(), WString::new());
-        for (i, val) in self.values.iter().enumerate() {
-            out[i].clone_from(val);
-        }
-    }
-
     /// Returns the variable's values.
     pub fn as_list(&self) -> &[WString] {
         &self.values

src/env_dispatch.rs

@@ -355,8 +355,11 @@ fn handle_read_limit_change(vars: &EnvStack) {
 }
 
 fn handle_fish_trace(vars: &EnvStack) {
-    let enabled = vars.get_unless_empty(L!("fish_trace")).is_some();
-    crate::trace::trace_set_enabled(enabled);
+    crate::trace::trace_set_enabled(
+        vars.get_unless_empty(L!("fish_trace"))
+            .map(|var| var.as_list().to_vec())
+            .unwrap_or_default(),
+    );
 }
 
 pub fn env_dispatch_init(vars: &EnvStack) {

src/trace.rs

@@ -3,13 +3,18 @@
 use crate::{common::escape, global_safety::RelaxedAtomicBool, prelude::*};
 
 static DO_TRACE: RelaxedAtomicBool = RelaxedAtomicBool::new(false);
+static DO_TRACE_ALL: RelaxedAtomicBool = RelaxedAtomicBool::new(false);
 
-pub fn trace_set_enabled(do_enable: bool) {
-    DO_TRACE.store(do_enable);
+pub fn trace_set_enabled(enable: Vec<WString>) {
+    DO_TRACE.store(!enable.is_empty());
+    DO_TRACE_ALL.store(enable.iter().any(|s| s == "all"));
 }
 
 /// return whether tracing is enabled.
 pub fn trace_enabled(parser: &Parser) -> bool {
+    if DO_TRACE_ALL.load() {
+        return true;
+    }
     if parser.scope().suppress_fish_trace {
         return false;
     }