Implementation:Apache Druid HjsonCompletions

Knowledge Sources	Apache_Druid
Domains	Web_Console, Editor_Autocompletion
Last Updated	2026-02-10 10:00 GMT

Overview

HjsonCompletions is a module that provides context-aware autocompletion for HJSON editing in the Ace Editor, generating completions based on the current JSON path and editing context.

Description

The module's main function, getHjsonCompletions, analyzes the text before the cursor to determine the current position within the JSON structure (path, current key, whether editing a key or value, and the surrounding object). It then uses JsonCompletionRule definitions to look up available completions for that path, filters them based on context (excluding already-present keys when editing a key, removing boolean/null literals when inside quotes for value editing), and converts them to the Ace Completion format with optional documentation HTML popups.

Usage

Used by the JsonInput component to provide intelligent autocompletion when editing ingestion specs, supervisor specs, compaction configurations, and other HJSON/JSON configuration inputs in the Druid web console.

Code Reference

Source Location

• Repository: Apache Druid
• File: web-console/src/ace-completions/hjson-completions.ts
• Lines: 1-133

Signature

export interface GetHjsonCompletionsOptions {
  jsonCompletions: JsonCompletionRule[];
  textBefore: string;
  charBeforePrefix: string;
  prefix: string;
}

export function getHjsonCompletions(options: GetHjsonCompletionsOptions): Ace.Completion[];

Import

import { getHjsonCompletions } from './ace-completions/hjson-completions';

I/O Contract

Inputs

Name	Type	Required	Description
jsonCompletions	JsonCompletionRule[]	Yes	Array of completion rule definitions describing available keys and values for each JSON path
textBefore	string	Yes	The full text content before the current cursor position in the editor
charBeforePrefix	string	Yes	The single character immediately before the autocompletion prefix (e.g., '"' or ':')
prefix	string	Yes	The current word being typed that triggered autocompletion

Outputs

Name	Type	Description
completions	Ace.Completion[]	An array of Ace Editor completion objects with name, value, score, meta, and optional docHTML

Usage Examples

Providing completions to an Ace Editor

const completions = getHjsonCompletions({
  jsonCompletions: ingestionSpecCompletionRules,
  textBefore: allTextBeforeCursor,
  charBeforePrefix: '"',
  prefix: 'type',
});
// Returns completions like: [{ name: 'type', value: 'type', score: 5, meta: 'property' }]

Related Pages

• Environment:Apache_Druid_Web_Console_Development