`visit` function of model namespaces disappeared

[olmokramer]

Checkboxes for prior research

• I've gone through Developer Guide and API reference
• I've checked AWS Forums and StackOverflow.
• I've searched for previous similar issues and didn't find any solution.

Describe the bug

When upgrading from SDK version 3.812.0 to version 3.996.0, I was surprised to find that the visit method of union namespaces is no longer available after a minor version upgrade. This seems to have happened in this commit but I couldn't find any mention of this in the release changelogs since that commit.

Regression Issue

• Select this option if this issue appears to be a regression.

SDK version number

@aws-sdk/client-* 3.996.0

Which JavaScript Runtime is this issue in?

Node.js

Details of the browser/Node.js/ReactNative version

v22.14.0

Reproduction Steps

import { ContentBlockDelta } from '@aws-sdk/client-bedrock-runtime';

function processContentBlockDelta(d: ContentBlockDelta) {
    return ContentBlockDelta.visit(d, {
        text() {
            // process text delta
        },
        // ... other members
    });
}

Observed Behavior

I get a type error: "Cannot use namespace 'ContentBlockDelta' as a value."

Expected Behavior

A visit function is provided to decide how to process a union.

Possible Solution

Revert the parts of 6362fe2 that remove the visit function.

Additional Information/Context

No response

[kuhe]

The visit functions were an internal API and weren't marked @public like the types they were adjacent to. They were removed because they duplicated the same functionality thousands of times in the SDK.

The same function can be implemented in a very small number of lines of code, and be compatible with all of the former shape-specific visit functions.

Please use the generic version below, which is compatible with any existing Visitor objects you may have.

import type {
  CitationsDelta,
  ContentBlockDelta,
  ImageBlockDelta,
  ReasoningContentBlockDelta,
  ToolResultBlockDelta,
  ToolUseBlockDelta,
} from "@aws-sdk/client-bedrock-runtime";

const myVisitor: ContentBlockDelta.Visitor<void> = {
  text(value: string) {
    console.log("text:", value);
  },
  toolUse(value: ToolUseBlockDelta) {
    void value;
  },
  toolResult(value: ToolResultBlockDelta[]) {
    void value;
  },
  reasoningContent(value: ReasoningContentBlockDelta) {
    void value;
  },
  citation(value: CitationsDelta) {
    void value;
  },
  image(value: ImageBlockDelta) {
    void value;
  },
  _(name: string, value: any) {
    console.log("$unknown:", name, value);
  },
};

type Visitor<T, R = void> = Omit<
  {
    [K in keyof T]: (value: T[K]) => R;
  },
  "$unknown"
> & {
  _(name: string, value: any): R;
};

const visit = <U extends object, V extends Visitor<U>>(unionData: U, visitor: V) => {
  if ("$unknown" in unionData && Array.isArray(unionData.$unknown)) {
    const [k, v] = unionData.$unknown;
    return visitor._(k, v);
  }
  const unionKey = Object.keys(unionData).filter((k) => k !== "__type")[0];
  return visitor[unionKey]?.(unionData[unionKey]);
};

const data: ContentBlockDelta.TextMember = {
  text: "hello",
};

visit(data, myVisitor);

const data2: ContentBlockDelta.$UnknownMember = {
  $unknown: ["text", "hello"],
};

visit(data2, myVisitor);

[olmokramer]

Thanks for the fast reply and the generic implementation! Didn't know the API wasn't public, sorry for the noise.

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