From d8575c97610b96e58a2858dc386ad61b8af55d9d Mon Sep 17 00:00:00 2001
From: Armando Belardo <11140328+armandobelardo@users.noreply.github.com>
Date: Fri, 28 Jun 2024 17:56:28 -0400
Subject: [PATCH] improvement: add x-fern-base-path to asyncapi extensions
 (#3953)

---
 .../openapi-ir-to-fern/src/FernDefnitionBuilder.ts  |  5 +++++
 .../openapi-parser/src/asyncapi/fernExtensions.ts   | 13 ++++++++++++-
 packages/cli/openapi-parser/src/asyncapi/parse.ts   |  4 +++-
 packages/cli/openapi-parser/src/parse.ts            |  3 +++
 4 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/packages/cli/openapi-ir-to-fern/src/FernDefnitionBuilder.ts b/packages/cli/openapi-ir-to-fern/src/FernDefnitionBuilder.ts
index faaa4399bcd..0c5dcc4d5f3 100644
--- a/packages/cli/openapi-ir-to-fern/src/FernDefnitionBuilder.ts
+++ b/packages/cli/openapi-ir-to-fern/src/FernDefnitionBuilder.ts
@@ -332,6 +332,11 @@ export class FernDefinitionBuilderImpl implements FernDefinitionBuilder {
     public addChannel(file: RelativeFilePath, { channel }: { channel: RawSchemas.WebSocketChannelSchema }): void {
         const fernFile = this.getOrCreateFile(file);
         fernFile.channel = channel;
+
+        const basePath = this.basePath;
+        if (basePath != null) {
+            fernFile.channel.path = path.join(basePath, channel.path);
+        }
     }
 
     public addChannelExample(
diff --git a/packages/cli/openapi-parser/src/asyncapi/fernExtensions.ts b/packages/cli/openapi-parser/src/asyncapi/fernExtensions.ts
index 309ebf0a5b0..623e22055ab 100644
--- a/packages/cli/openapi-parser/src/asyncapi/fernExtensions.ts
+++ b/packages/cli/openapi-parser/src/asyncapi/fernExtensions.ts
@@ -28,7 +28,18 @@ export const FernAsyncAPIExtension = {
      *             value:
      *              data: "12340213"
      */
-    FERN_EXAMPLES: "x-fern-examples"
+    FERN_EXAMPLES: "x-fern-examples",
+
+    /**
+     * Prepends the configured base path to all of the endpoint paths.
+     *
+     * x-fern-base-path: /v1
+     * servers:
+     *   - url: https://api.example.com
+     * paths:
+     *   /path/to/my/endpoint:
+     */
+    BASE_PATH: "x-fern-base-path"
 } as const;
 
 export type FernAsyncAPIExtension = Values<typeof FernAsyncAPIExtension>;
diff --git a/packages/cli/openapi-parser/src/asyncapi/parse.ts b/packages/cli/openapi-parser/src/asyncapi/parse.ts
index 9cbaa8ffd2c..da0667aa1fa 100644
--- a/packages/cli/openapi-parser/src/asyncapi/parse.ts
+++ b/packages/cli/openapi-parser/src/asyncapi/parse.ts
@@ -26,6 +26,7 @@ import { AsyncAPIV2 } from "./v2";
 export interface AsyncAPIIntermediateRepresentation {
     schemas: Record<SchemaId, Schema>;
     channel: WebsocketChannel | undefined;
+    basePath: string | undefined;
 }
 
 export function parseAsyncAPI({
@@ -214,7 +215,8 @@ export function parseAsyncAPI({
         schemas: Object.fromEntries(
             Object.entries(schemas).map(([id, schema]) => [id, convertSchemaWithExampleToSchema(schema)])
         ),
-        channel: parsedChannel
+        channel: parsedChannel,
+        basePath: getExtension<string | undefined>(document, FernAsyncAPIExtension.BASE_PATH)
     };
 }
 
diff --git a/packages/cli/openapi-parser/src/parse.ts b/packages/cli/openapi-parser/src/parse.ts
index 74300b7d7f3..9f4ad0ab2a5 100644
--- a/packages/cli/openapi-parser/src/parse.ts
+++ b/packages/cli/openapi-parser/src/parse.ts
@@ -109,6 +109,9 @@ export async function parse({
                     ...parsedAsyncAPI.schemas
                 };
             }
+            if (parsedAsyncAPI.basePath != null) {
+                ir.basePath = parsedAsyncAPI.basePath;
+            }
         } else {
             taskContext.failAndThrow(`${spec.absoluteFilepath} is not a valid OpenAPI or AsyncAPI file`);
         }