Clarify usage with documentation and naming

Author: timsaucer

datafusion/ffi/src/config/mod.rs

@@ -81,11 +81,15 @@ impl TryFrom<FFI_ConfigOptions> for ConfigOptions {
 }
 
 pub trait ExtensionOptionsFFIProvider {
-    fn ffi_extension<C: ConfigExtension + Clone + Default>(&self) -> Option<C>;
+    /// Extract a [`ConfigExtension`]. This method should attempt to first extract
+    /// the extension from the local options when possible. Should that fail, it
+    /// should attempt to extract the FFI options and then convert them to the
+    /// desired [`ConfigExtension`].
+    fn local_or_ffi_extension<C: ConfigExtension + Clone + Default>(&self) -> Option<C>;
 }
 
 impl ExtensionOptionsFFIProvider for ConfigOptions {
-    fn ffi_extension<C: ConfigExtension + Clone + Default>(&self) -> Option<C> {
+    fn local_or_ffi_extension<C: ConfigExtension + Clone + Default>(&self) -> Option<C> {
         self.extensions
             .get::<C>()
             .map(|v| v.to_owned())
@@ -98,7 +102,7 @@ impl ExtensionOptionsFFIProvider for ConfigOptions {
 }
 
 impl ExtensionOptionsFFIProvider for TableOptions {
-    fn ffi_extension<C: ConfigExtension + Clone + Default>(&self) -> Option<C> {
+    fn local_or_ffi_extension<C: ConfigExtension + Clone + Default>(&self) -> Option<C> {
         self.extensions
             .get::<C>()
             .map(|v| v.to_owned())

datafusion/ffi/tests/ffi_config.rs

@@ -44,13 +44,13 @@ mod tests {
 
         // Verify default values are as expected
         let returned_config: ExternalConfig = config
-            .ffi_extension()
+            .local_or_ffi_extension()
             .expect("should have external config extension");
         assert_eq!(returned_config, ExternalConfig::default());
 
         config.set("external_config.is_enabled", "false")?;
         let returned_config: ExternalConfig = config
-            .ffi_extension()
+            .local_or_ffi_extension()
             .expect("should have external config extension");
         assert!(!returned_config.is_enabled);
 
@@ -74,14 +74,14 @@ mod tests {
 
         // Verify default values are as expected
         let returned_options: ExternalConfig = table_options
-            .ffi_extension()
+            .local_or_ffi_extension()
             .expect("should have external config extension");
 
         assert_eq!(returned_options, ExternalConfig::default());
 
         table_options.set("external_config.is_enabled", "false")?;
         let returned_options: ExternalConfig = table_options
-            .ffi_extension()
+            .local_or_ffi_extension()
             .expect("should have external config extension");
         assert!(!returned_options.is_enabled);
 
@@ -105,7 +105,7 @@ mod tests {
         // Verify default values are as expected
         let returned_config: ExternalConfig = config
             .options()
-            .ffi_extension()
+            .local_or_ffi_extension()
             .expect("should have external config extension");
         assert_eq!(returned_config, ExternalConfig::default());
 
@@ -115,7 +115,7 @@ mod tests {
         );
         let returned_config: ExternalConfig = config
             .options()
-            .ffi_extension()
+            .local_or_ffi_extension()
             .expect("should have external config extension");
         assert!(!returned_config.is_enabled);