fix(plugin): export read-only table fields to the plugin API

Signed-off-by: Grzegorz Nosek <[email protected]>

falco_plugin/src/plugin/exported_tables/field/readonly.rs

@@ -1,3 +1,4 @@
+use crate::internals::tables::export::DynamicFieldValue;
 use crate::plugin::exported_tables::field_value::traits::FieldValue;
 use crate::plugin::exported_tables::field_value::traits::{seal, StaticField};
 use crate::plugin::exported_tables::metadata::HasMetadata;
@@ -52,3 +53,11 @@ impl<T: StaticField> StaticField for Readonly<T> {
     const TYPE_ID: FieldTypeId = T::TYPE_ID;
     const READONLY: bool = true;
 }
+
+impl<T: TryFrom<DynamicFieldValue>> TryFrom<DynamicFieldValue> for Readonly<T> {
+    type Error = T::Error;
+
+    fn try_from(value: DynamicFieldValue) -> Result<Self, Self::Error> {
+        Ok(Self(T::try_from(value)?))
+    }
+}

falco_plugin_tests/tests/parse_table_api.rs

@@ -23,6 +23,7 @@ type RemainingEntryTable = export::Table<u64, RemainingCounter>;
 #[derive(export::Entry)]
 struct RemainingCounter {
     remaining: export::Public<u64>,
+    readonly: export::Readonly<u64>,
 }
 
 // same table, but imported
@@ -33,6 +34,7 @@ type RemainingCounterImport = import::Entry<Arc<RemainingCounterImportMetadata>>
 #[entry_type(RemainingCounterImport)]
 struct RemainingCounterImportMetadata {
     remaining: import::Field<u64, RemainingCounterImport>,
+    readonly: import::Field<u64, RemainingCounterImport>,
 }
 
 struct DummyPlugin {
@@ -145,6 +147,10 @@ impl ParsePlugin for DummyPlugin {
         let w = &parse_input.writer;
         let entry = self.remaining_table_import.create_entry(w)?;
         entry.set_remaining(w, &remaining)?;
+        anyhow::ensure!(
+            entry.set_readonly(w, &1).is_err(),
+            "setting a read-only field succeeded"
+        );
         let _ = self
             .remaining_table_import
             .insert(r, w, &event_num, entry)?;