Skip to content

lang-core

Directory actions

More options

Directory actions

More options

Latest commit

 

History

History

lang-core

README.md

@openuidev/lang-core

Framework-agnostic core for OpenUI Lang. This is the parser, prompt-generation, runtime-evaluation, and type layer used by the framework packages.

npm version monthly downloads License: MIT

Links: OpenUI Lang docs | GitHub repo

Install

npm install @openuidev/lang-core
# or
pnpm add @openuidev/lang-core

What this package does

@openuidev/lang-core has no React, Vue, or Svelte dependency. Use it when you need to:

  • Parse OpenUI Lang text into a typed element tree (one-shot or streaming)
  • Generate system prompts from a component spec + tool definitions
  • Evaluate reactive expressions, $variables, and query results at runtime
  • Merge incremental edits into existing programs

If you're building a framework-specific app, use @openuidev/react-lang, @openuidev/vue-lang or @openuidev/svelte-lang instead. It re-exports everything from this package plus framework-specific components and hooks.

Quick Start

Parse OpenUI Lang

import { createParser } from "@openuidev/lang-core";

const parser = createParser(libraryJsonSchema);
const result = parser.parse(`
root = Stack([header, content])
header = CardHeader("Hello")
content = TextContent("World")
`);

console.log(result.root);       // ElementNode tree
console.log(result.meta);       // { incomplete, unresolved, statementCount, validationErrors }

Streaming parser

import { createStreamingParser } from "@openuidev/lang-core";

const sp = createStreamingParser(libraryJsonSchema);

// Feed chunks as they arrive from the LLM
const result1 = sp.set("root = Stack([header])\n");
const result2 = sp.set("root = Stack([header])\nheader = CardHeader(\"Hello\")\n");
// result2.root now resolves the forward reference

Generate a system prompt

import { generatePrompt, type PromptSpec } from "@openuidev/lang-core";
import componentSpec from "./generated/component-spec.json";

const prompt = generatePrompt({
  ...componentSpec,
  tools: myToolSpecs,
  toolCalls: true,
  bindings: true,
  editMode: true,
  preamble: "You build dashboards.",
});

Merge incremental edits

import { mergeStatements } from "@openuidev/lang-core";

const original = `root = Stack([header, tbl])\nheader = CardHeader("Tickets")\ntbl = Table([...])`;
const patch = `root = Stack([header, chart, tbl])\nchart = PieChart(...)`;
const merged = mergeStatements(original, patch);
// header and tbl kept from original, root replaced, chart added

API

Parser

Export Description
createParser(schema) One-shot parser for complete text
createStreamingParser(schema) Incremental parser for streaming input
parse(input, schema) Convenience one-shot parse

Prompt Generation

Export Description
generatePrompt(spec) Generate a system prompt from a PromptSpec

PromptSpec includes component signatures, tool definitions (ToolSpec[]), feature flags (toolCalls, bindings, editMode, inlineMode), examples, and custom rules.

ToolSpec describes a tool for prompt generation (name, description, inputSchema, outputSchema). Shape inspired by MCP's tool schema.

Runtime

Export Description
createQueryManager(toolProvider) Manages Query/Mutation execution and caching
createStore() Reactive store for $variables and form state
evaluate(ast, context) Evaluate an AST node to a concrete value
evaluateElementProps(root, context) Recursively evaluate all props in an element tree
extractToolResult(result) Extract data from an MCP callTool response
mergeStatements(original, patch) Merge incremental edits by statement name

Types

import type {
  PromptSpec,
  ToolSpec,
  ParseResult,
  ElementNode,
  ToolProvider,
  McpClientLike,
  QueryManager,
  Store,
  OpenUIError,
} from "@openuidev/lang-core";

Documentation

License

MIT