refactor(transformers): transform date only if date is format date-time and not date

docs/openapi-ts/plugins/transformers.md

@@ -79,7 +79,16 @@ export default {
 };
 ```
 
-This will generate types that use `Date` instead of `string` and appropriate transformers. Note that third-party date packages are not supported at the moment.
+This will generate types that use `Date` instead of `string` and appropriate transformers for fields with `format: "date-time"`. Fields with `format: "date"` will remain as strings since they represent date-only values (e.g., `2024-01-20`) without time information.
+
+::: tip
+The OpenAPI specification defines two date formats:
+
+- `date-time`: Full timestamp with time and timezone (e.g., `2024-01-20T15:30:00Z`) - **converted to `Date`**
+- `date`: Date only without time (e.g., `2024-01-20`) - **kept as `string`**
+  :::
+
+Note that third-party date packages are not supported at the moment.
 
 ## BigInt
 

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

@@ -38,7 +38,7 @@ export const bigIntExpressions: ExpressionTransformer = ({ dataExpression, schem
 };
 
 export const dateExpressions: ExpressionTransformer = ({ dataExpression, schema }) => {
-  if (schema.type !== 'string' || !(schema.format === 'date' || schema.format === 'date-time')) {
+  if (schema.type !== 'string' || !(schema.format === 'date-time')) {
     return;
   }
 

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

@@ -20,7 +20,8 @@ export type UserConfig = Plugin.Name<'@hey-api/transformers'> &
      */
     bigInt?: boolean;
     /**
-     * Convert date strings into Date objects?
+     * Convert date-time strings into Date objects?
+     * Only affects fields with format "date-time", not "date".
      *
      * @default true
      */
@@ -45,7 +46,8 @@ export type Config = Plugin.Name<'@hey-api/transformers'> &
      */
     bigInt: boolean;
     /**
-     * Convert date strings into Date objects?
+     * Convert date-time strings into Date objects?
+     * Only affects fields with format "date-time", not "date".
      *
      * @default true
      */

packages/openapi-ts/src/plugins/@hey-api/typescript/v1/toAst/string.ts

@@ -21,7 +21,7 @@ export const stringToAst = ({
       return $.type.or($.type('Blob'), $.type('File'));
     }
 
-    if (schema.format === 'date-time' || schema.format === 'date') {
+    if (schema.format === 'date-time') {
       // TODO: parser - add ability to skip type transformers
       if (plugin.getPlugin('@hey-api/transformers')?.config.dates) {
         return $.type('Date');