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plpgsql-parse

Comment preserving PL/pgSQL parser. A wrapper around plpgsql-parser and plpgsql-deparser that preserves -- line comments inside PL/pgSQL function bodies through parse-deparse round trips.

Installation

npm install plpgsql-parse

Features

  • Body Comment Preservation -- Retains -- line comments inside PL/pgSQL function bodies ($$...$$) through parse-deparse cycles
  • Outer SQL Comment Preservation -- Preserves comments and whitespace outside function definitions via pgsql-parse
  • Idempotent Round-Trips -- parse -> deparse -> parse -> deparse produces identical output
  • Non-Invasive -- Does not modify plpgsql-parser, plpgsql-deparser, or any other upstream packages

How It Works

  1. Uses pgsql-parse for outer SQL comment and whitespace preservation
  2. For each PL/pgSQL function, scans the $$...$$ body to extract -- comments with line numbers
  3. Associates each comment with the nearest following PL/pgSQL statement (anchor)
  4. On deparse, re-injects comments by matching statement keywords against the deparsed output

API

Parse

import { parseSync, deparseSync, loadModule } from 'plpgsql-parse';

await loadModule();

const result = parseSync(`
-- Create a counter function
CREATE FUNCTION get_count() RETURNS int LANGUAGE plpgsql AS $$
BEGIN
  -- Count active users
  RETURN (SELECT count(*) FROM users WHERE active);
END;
$$;
`);

// result.enhanced contains outer SQL comments/whitespace
// result.functions contains body comments for each PL/pgSQL function
const sql = deparseSync(result);
// Output preserves both outer and body comments

Credits

Built on the excellent work of several contributors:

  • Dan Lynch -- official maintainer since 2018 and architect of the current implementation
  • Lukas Fittl for libpg_query -- the core PostgreSQL parser that powers this project