Fixing widespread case of nullable dates in tranformers

Author: Freddis

packages/openapi-ts/src/plugins/@hey-api/transformers/plugin.ts

@@ -57,9 +57,11 @@ const bigIntExpressions = ({
 
 const dateExpressions = ({
   dataExpression,
+  completeFieldSchema,
 }: {
   dataExpression?: ts.Expression | string;
-}): Array<ts.Expression> => {
+  completeFieldSchema: IR.SchemaObject[],
+}): Array<ts.Expression | ts.Statement> => {
   const identifierDate = compiler.identifier({ text: 'Date' });
 
   if (typeof dataExpression === 'string') {
@@ -72,6 +74,25 @@ const dateExpressions = ({
   }
 
   if (dataExpression) {
+
+    if (completeFieldSchema[1]?.type === 'null') {
+      const ifStatement = ts.factory.createIfStatement(
+        ts.factory.createBinaryExpression(
+          dataExpression,
+          ts.SyntaxKind.EqualsEqualsEqualsToken,
+          ts.factory.createNull()
+        ),
+        ts.factory.createExpressionStatement(
+          ts.factory.createNewExpression(
+            identifierDate,
+            undefined,
+            [dataExpression]
+          )
+        ),
+      );
+      return [ifStatement];
+    }
+
     return [
       compiler.assignment({
         left: dataExpression,
@@ -186,11 +207,13 @@ const processSchemaType = ({
   dataExpression,
   plugin,
   schema,
+  completeFieldSchema,
 }: {
   context: IR.Context;
   dataExpression?: ts.Expression | string;
   plugin: Plugin.Instance<Config>;
   schema: IR.SchemaObject;
+  completeFieldSchema?: IR.SchemaObject[];
 }): Array<ts.Expression | ts.Statement> => {
   const file = context.file({ id: transformersId })!;
 
@@ -369,7 +392,7 @@ const processSchemaType = ({
     schema.type === 'string' &&
     (schema.format === 'date' || schema.format === 'date-time')
   ) {
-    return dateExpressions({ dataExpression });
+    return dateExpressions({ dataExpression, completeFieldSchema: completeFieldSchema ?? [] });
   }
 
   if (plugin.bigInt && schema.type === 'integer' && schema.format === 'int64') {
@@ -382,7 +405,7 @@ const processSchemaType = ({
         context,
         dataExpression: 'item',
         plugin,
-        schema: schema.items[0]!,
+        schema: schema.items[0]!
       });
     }
 
@@ -401,6 +424,7 @@ const processSchemaType = ({
           dataExpression: dataExpression || 'item',
           plugin,
           schema: item,
+          completeFieldSchema: [...schema.items],
         });
         if (nodes.length) {
           if (dataExpression) {