From 259633d78f1e5587acf1e90381efe8ce2a5a14cc Mon Sep 17 00:00:00 2001
From: Simon Dick <simond@irrelevant.org>
Date: Sat, 19 Sep 2026 21:31:09 +0100
Subject: [PATCH] Fix SetVar(name, NULL, ...) to succeed silently on a missing
 variable

Real SetVar(name, NULL, 0, flags), and DeleteVar which is implemented
in terms of it, succeed silently when the variable doesn't exist
(verified against real Kickstart via Copperline). Both the local-vars
path and the ENV:-backed global path were wrongly returning
ERROR_OBJECT_NOT_FOUND instead.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
---
 crates/volamos-core/src/dosvar.rs | 41 +++++++++++++++++++++----------
 1 file changed, 28 insertions(+), 13 deletions(-)

diff --git a/crates/volamos-core/src/dosvar.rs b/crates/volamos-core/src/dosvar.rs
index 1285e40..5d0f9e3 100644
--- a/crates/volamos-core/src/dosvar.rs
+++ b/crates/volamos-core/src/dosvar.rs
@@ -81,14 +81,22 @@ fn global_set(vfs: Option<&Vfs>, name: &[u8], content: &[u8]) -> Result<(), i32>
     std::fs::write(&resolved.host_path, content).map_err(|e| map_io_error(&e))
 }
 
-/// Deletes global variable `name`'s `ENV:name` file on `vfs`.
+/// Deletes global variable `name`'s `ENV:name` file on `vfs`. Real
+/// `SetVar(name, NULL, 0, flags)` succeeds silently when the variable
+/// doesn't exist (verified against real Kickstart), so a missing file
+/// is not an error here.
 fn global_delete(vfs: Option<&Vfs>, name: &[u8]) -> Result<(), i32> {
     let vfs = vfs.ok_or(ERROR_OBJECT_NOT_FOUND)?;
     let amiga_path = format!("ENV:{}", String::from_utf8_lossy(name));
-    let resolved = vfs
-        .resolve_with_amiga_path(&amiga_path, ResolveMode::MustExist)
-        .map_err(|e| map_vfs_error(&e))?;
-    std::fs::remove_file(&resolved.host_path).map_err(|e| map_io_error(&e))
+    let resolved = match vfs.resolve_with_amiga_path(&amiga_path, ResolveMode::MustExist) {
+        Ok(resolved) => resolved,
+        Err(_) => return Ok(()),
+    };
+    match std::fs::remove_file(&resolved.host_path) {
+        Ok(()) => Ok(()),
+        Err(e) if e.kind() == std::io::ErrorKind::NotFound => Ok(()),
+        Err(e) => Err(map_io_error(&e)),
+    }
 }
 
 const DOSTRUE: u32 = 0xFFFF_FFFF;
@@ -134,11 +142,8 @@ fn set_var(
             global_delete(dos.vfs.as_ref(), &raw_name)
         } else {
             let key = String::from_utf8_lossy(&raw_name).to_ascii_uppercase();
-            if dos.local_vars.remove(&key).is_some() {
-                Ok(())
-            } else {
-                Err(ERROR_OBJECT_NOT_FOUND)
-            }
+            dos.local_vars.remove(&key);
+            Ok(())
         };
     }
 
@@ -383,11 +388,13 @@ mod tests {
     }
 
     #[test]
-    fn delete_missing_var_is_an_error() {
+    fn delete_missing_var_succeeds_silently() {
+        // Real SetVar(name, NULL, 0, flags) on a variable that doesn't
+        // exist succeeds (verified against real Kickstart), it doesn't
+        // raise ERROR_OBJECT_NOT_FOUND.
         let (mut mem, mut dos) = setup();
         write_c_string(&mut mem, 0x100, b"NOPE");
-        let err = set_var(&mem, &mut dos, 0x100, 0, 0, 0).unwrap_err();
-        assert_eq!(err, ERROR_OBJECT_NOT_FOUND);
+        set_var(&mem, &mut dos, 0x100, 0, 0, 0).expect("delete of missing var should succeed");
     }
 
     #[test]
@@ -440,6 +447,14 @@ mod tests {
         assert_eq!(read_c_string(&mem, 0x300), b"hello");
     }
 
+    #[test]
+    fn global_delete_of_missing_var_succeeds_silently() {
+        let (mut mem, mut dos, _tmp) = setup_with_env();
+        write_c_string(&mut mem, 0x100, b"NOPE");
+        set_var(&mem, &mut dos, 0x100, 0, 0, GVF_GLOBAL_ONLY)
+            .expect("delete of missing global var should succeed");
+    }
+
     #[test]
     fn global_delete_removes_the_real_file() {
         let (mut mem, mut dos, tmp) = setup_with_env();