Fix casting db type as nullable rather than optional (#474)

* Fix casting db type as nullable rather than optional

* Add comment about Nullable.t use

Author: JonoPrest

codegenerator/cli/templates/static/codegen/src/db/DbFunctions.res

@@ -98,10 +98,13 @@ module ChainMetadata = {
     @as("chain_id") chainId: int,
     @as("block_height") blockHeight: int,
     @as("start_block") startBlock: int,
-    @as("end_block") endBlock: option<int>,
-    @as("first_event_block_number") firstEventBlockNumber: option<int>,
-    @as("latest_processed_block") latestProcessedBlock: option<int>,
-    @as("num_events_processed") numEventsProcessed: option<int>,
+    // The values below could use `Js.Null.t` instead of `Js.Nullable.t`
+    // It just needs to be confiremed that the postgres lib never returns
+    // undefined.
+    @as("end_block") endBlock: Js.Nullable.t<int>,
+    @as("first_event_block_number") firstEventBlockNumber: Js.Nullable.t<int>,
+    @as("latest_processed_block") latestProcessedBlock: Js.Nullable.t<int>,
+    @as("num_events_processed") numEventsProcessed: Js.Nullable.t<int>,
     @as("is_hyper_sync") poweredByHyperSync: bool,
     @as("num_batches_fetched") numBatchesFetched: int,
     @as("latest_fetched_block_number") latestFetchedBlockNumber: int,

codegenerator/cli/templates/static/codegen/src/eventFetching/ChainFetcher.res

@@ -267,14 +267,14 @@ let makeFromDbState = async (
     }) => {
       // on restart, reset the events_processed gauge to the previous state
       switch numEventsProcessed {
-      | Some(numEventsProcessed) =>
+      | Value(numEventsProcessed) =>
         Prometheus.setEventsProcessedGuage(~number=numEventsProcessed, ~chainId)
-      | None => () // do nothing if no events have been processed yet for this chain
+      | Null | Undefined => () // do nothing if no events have been processed yet for this chain
       }
       (
-        firstEventBlockNumber,
-        latestProcessedBlock,
-        numEventsProcessed,
+        firstEventBlockNumber->Js.Nullable.toOption,
+        latestProcessedBlock->Js.Nullable.toOption,
+        numEventsProcessed->Js.Nullable.toOption,
         Env.updateSyncTimeOnRestart
           ? None
           : timestampCaughtUpToHeadOrEndblock->Js.Nullable.toOption,

codegenerator/cli/templates/static/codegen/src/globalState/GlobalState.res

@@ -152,10 +152,10 @@ let updateChainMetadataTable = async (cm: ChainManager.t, ~throttler: Throttler.
         startBlock: cf.chainConfig.startBlock,
         blockHeight: cf.currentBlockHeight,
         //optional fields
-        endBlock: cf.chainConfig.endBlock, //this is already optional
-        firstEventBlockNumber: cf->ChainFetcher.getFirstEventBlockNumber,
-        latestProcessedBlock: cf.latestProcessedBlock, // this is already optional
-        numEventsProcessed: Some(cf.numEventsProcessed),
+        endBlock: cf.chainConfig.endBlock->Js.Nullable.fromOption, //this is already optional
+        firstEventBlockNumber: cf->ChainFetcher.getFirstEventBlockNumber->Js.Nullable.fromOption,
+        latestProcessedBlock: cf.latestProcessedBlock->Js.Nullable.fromOption, // this is already optional
+        numEventsProcessed: Value(cf.numEventsProcessed),
         poweredByHyperSync: (cf.sourceManager->SourceManager.getActiveSource).poweredByHyperSync,
         numBatchesFetched: cf.numBatchesFetched,
         latestFetchedBlockNumber: latestFetchedBlock.blockNumber,