[Rust] Fix custom SecretsProvider impl requiring data to be passed back in get_data

We want to provide no value in the case of the key not having an associated value

Author: emesare

rust/src/secrets_provider.rs

@@ -8,7 +8,7 @@ use crate::string::{BnString, IntoCStr};
 
 pub trait SecretsProvider {
     fn has_data(&mut self, key: &str) -> bool;
-    fn get_data(&mut self, key: &str) -> String;
+    fn get_data(&mut self, key: &str) -> Option<String>;
     fn store_data(&mut self, key: &str, data: &str) -> bool;
     fn delete_data(&mut self, key: &str) -> bool;
 }
@@ -126,8 +126,10 @@ unsafe extern "C" fn cb_get_data<C: SecretsProvider>(
     key: *const c_char,
 ) -> *mut c_char {
     let ctxt: &mut C = &mut *(ctxt as *mut C);
-    let result = ctxt.get_data(&CStr::from_ptr(key).to_string_lossy());
-    BnString::into_raw(BnString::new(result))
+    match ctxt.get_data(&CStr::from_ptr(key).to_string_lossy()) {
+        Some(result) => BnString::into_raw(BnString::new(result)),
+        None => std::ptr::null_mut(),
+    }
 }
 
 unsafe extern "C" fn cb_store_data<C: SecretsProvider>(

rust/tests/secrets_provider.rs

@@ -17,8 +17,12 @@ impl SecretsProvider for MySecretsProvider {
         key == "my_key"
     }
 
-    fn get_data(&mut self, key: &str) -> String {
-        if key == "my_key" { "my_value" } else { "" }.to_string()
+    fn get_data(&mut self, key: &str) -> Option<String> {
+        if key == "my_key" {
+            Some("my_value".to_string())
+        } else {
+            None
+        }
     }
 
     fn store_data(&mut self, _key: &str, _data: &str) -> bool {