Add support for server side interceptors (#982)

packages/connect-web-bench/README.md

@@ -10,5 +10,5 @@ it like a web server would usually do.
 
 | code generator | bundle size        | minified               | compressed           |
 |----------------|-------------------:|-----------------------:|---------------------:|
-| connect        | 117,695 b | 51,217 b | 13,730 b |
+| connect        | 117,734 b | 51,217 b | 13,697 b |
 | grpc-web       | 415,212 b    | 300,936 b    | 53,420 b |

packages/connect/src/implementation.spec.ts

@@ -33,6 +33,7 @@ describe("createHandlerContext()", function () {
     method: TestService.methods.unary,
     protocolName: "foo",
     requestMethod: "GET",
+    url: "https://example.com/foo",
   };
 
   describe("signal", function () {

packages/connect/src/implementation.ts

@@ -18,10 +18,10 @@ import type {
   MessageType,
   MethodIdempotency,
   MethodInfo,
-  MethodKind,
   PartialMessage,
   ServiceType,
 } from "@bufbuild/protobuf";
+import { MethodKind } from "@bufbuild/protobuf";
 import { ConnectError } from "./connect-error.js";
 import { Code } from "./code.js";
 import {
@@ -124,6 +124,11 @@ export interface HandlerContext {
    * Per RPC context values that can be used to pass data to handlers.
    */
   readonly values: ContextValues;
+
+  /**
+   * The URL received by the server.
+   */
+  readonly url: string;
 }
 
 /**
@@ -134,6 +139,7 @@ interface HandlerContextInit {
   method: MethodInfo;
   protocolName: string;
   requestMethod: string;
+  url: string;
   timeoutMs?: number;
   shutdownSignal?: AbortSignal;
   requestSignal?: AbortSignal;

packages/connect/src/interceptor.ts

@@ -21,7 +21,7 @@ import type {
 import type { ContextValues } from "./context-values.js";
 
 /**
- * An interceptor can add logic to clients, similar to the decorators
+ * An interceptor can add logic to clients or servers, similar to the decorators
  * or middleware you may have seen in other libraries. Interceptors may
  * mutate the request and response, catch errors and retry/recover, emit
  * logs, or do nearly everything else.
@@ -40,6 +40,10 @@ import type { ContextValues } from "./context-values.js";
  * actual HTTP request is run by the transport. The response then comes back
  * through all layers and is returned to the client.
  *
+ * Similarly, a request received by a server goes through the outermost layer
+ * first. In the center, the actual HTTP request is received by the handler. The
+ * response then comes back through all layers and is returned to the client.
+ *
  * To implement that layering, Interceptors are functions that wrap a call
  * invocation. In an array of interceptors, the interceptor at the end of
  * the array is applied first.
@@ -147,7 +151,8 @@ interface RequestCommon<I extends Message<I>, O extends Message<O>> {
   readonly method: MethodInfo<I, O>;
 
   /**
-   * The URL the request is going to hit.
+   * The URL the request is going to hit for the clients or the
+   * URL received by the server.
    */
   readonly url: string;
 
@@ -195,3 +200,24 @@ interface ResponseCommon<I extends Message<I>, O extends Message<O>> {
    */
   readonly trailer: Headers;
 }
+
+/**
+ * applyInterceptors takes the given UnaryFn or ServerStreamingFn, and wraps
+ * it with each of the given interceptors, returning a new UnaryFn or
+ * ServerStreamingFn.
+ */
+export function applyInterceptors<T>(
+  next: T,
+  interceptors: Interceptor[] | undefined,
+): T {
+  return (
+    (interceptors
+      ?.concat()
+      .reverse()
+      .reduce(
+        // eslint-disable-next-line @typescript-eslint/no-unsafe-argument
+        (n, i) => i(n),
+        next as any, // eslint-disable-line @typescript-eslint/no-explicit-any
+      ) as T) ?? next
+  );
+}

packages/connect/src/protocol-connect/handler-factory.ts

@@ -190,6 +190,7 @@ function createUnaryHandler<I extends Message<I>, O extends Message<O>>(
       shutdownSignal: opt.shutdownSignal,
       requestSignal: req.signal,
       requestHeader: req.header,
+      url: req.url,
       responseHeader: {
         [headerContentType]: type.binary
           ? contentTypeUnaryProto
@@ -241,7 +242,12 @@ function createUnaryHandler<I extends Message<I>, O extends Message<O>>(
         serialization,
         reqBody,
       );
-      const output = await invokeUnaryImplementation(spec, context, input);
+      const output = await invokeUnaryImplementation(
+        spec,
+        context,
+        input,
+        opt.interceptors,
+      );
       body = serialization.getO(type.binary).serialize(output);
     } catch (e) {
       let error: ConnectError | undefined;
@@ -375,6 +381,7 @@ function createStreamHandler<I extends Message<I>, O extends Message<O>>(
       shutdownSignal: opt.shutdownSignal,
       requestSignal: req.signal,
       requestHeader: req.header,
+      url: req.url,
       responseHeader: {
         [headerContentType]: type.binary
           ? contentTypeStreamProto
@@ -422,6 +429,7 @@ function createStreamHandler<I extends Message<I>, O extends Message<O>>(
     const it = transformInvokeImplementation<I, O>(
       spec,
       context,
+      opt.interceptors,
     )(inputIt)[Symbol.asyncIterator]();
     const outputIt = pipe(
       // We wrap the iterator in an async iterator to ensure that the

packages/connect/src/protocol-grpc-web/handler-factory.ts

@@ -131,6 +131,7 @@ function createHandler<I extends Message<I>, O extends Message<O>>(
       shutdownSignal: opt.shutdownSignal,
       requestSignal: req.signal,
       requestHeader: req.header,
+      url: req.url,
       responseHeader: {
         [headerContentType]: type.binary ? contentTypeProto : contentTypeJson,
       },
@@ -173,6 +174,7 @@ function createHandler<I extends Message<I>, O extends Message<O>>(
     const it = transformInvokeImplementation<I, O>(
       spec,
       context,
+      opt.interceptors,
     )(inputIt)[Symbol.asyncIterator]();
     const outputIt = pipe(
       // We wrap the iterator in an async iterator to ensure that the

packages/connect/src/protocol-grpc/handler-factory.ts

@@ -122,6 +122,7 @@ function createHandler<I extends Message<I>, O extends Message<O>>(
       shutdownSignal: opt.shutdownSignal,
       requestSignal: req.signal,
       requestHeader: req.header,
+      url: req.url,
       responseHeader: {
         [headerContentType]: type.binary ? contentTypeProto : contentTypeJson,
       },
@@ -159,6 +160,7 @@ function createHandler<I extends Message<I>, O extends Message<O>>(
     const it = transformInvokeImplementation<I, O>(
       spec,
       context,
+      opt.interceptors,
     )(inputIt)[Symbol.asyncIterator]();
     const outputIt = pipe(
       // We wrap the iterator in an async iterator to ensure that the