feat: add support for accountId in configValueProvider (#1252)

* feat: add support for accountId in configValueProvider

* chore: add changeset

.changeset/brown-bags-leave.md

@@ -0,0 +1,5 @@
+---
+"@smithy/middleware-endpoint": minor
+---
+
+add support for accountId in configValueProvider

packages/middleware-endpoint/src/adaptors/createConfigValueProvider.spec.ts

@@ -31,6 +31,17 @@ describe(createConfigValueProvider.name, () => {
     expect(await createConfigValueProvider("credentialScope", "CredentialScope", config)()).toEqual("cred-scope");
   });
 
+  it("uses a special lookup for accountId", async () => {
+    const config = {
+      credentials: async () => {
+        return {
+          accountId: "123456789012",
+        };
+      },
+    };
+    expect(await createConfigValueProvider("accountId", "AccountId", config)()).toEqual("123456789012");
+  });
+
   it("should normalize endpoint objects into URLs", async () => {
     const sampleUrl = "https://aws.amazon.com/";
     const config = {

packages/middleware-endpoint/src/adaptors/createConfigValueProvider.ts

@@ -31,6 +31,15 @@ export const createConfigValueProvider = <Config extends Record<string, unknown>
       return configValue;
     };
   }
+
+  if (configKey === "accountId" || canonicalEndpointParamKey === "AccountId") {
+    return async () => {
+      const credentials = typeof config.credentials === "function" ? await config.credentials() : config.credentials;
+      const configValue: string = credentials?.accountId ?? credentials?.AccountId;
+      return configValue;
+    };
+  }
+
   if (configKey === "endpoint" || canonicalEndpointParamKey === "endpoint") {
     return async () => {
       const endpoint = await configProvider();