prql-js

JavaScript bindings for prqlc.

Installation

npm install prql-js

Usage

Currently these functions are exposed

function compile(prql_query: string, options?: CompileOptions): string;

function prql_to_pl(prql_query: string): string;

function pl_to_prql(pl_json: string): string;

function pl_to_rq(pl_json: string): string;

function rq_to_sql(rq_json: string): string;

From Node.js

Direct usage

const prqljs = require("prql-js");

const sql = prqljs.compile(`from employees | select first_name`);
console.log(sql);

Options

const opts = new prql.CompileOptions();
opts.target = "sql.mssql";
opts.format = false;
opts.signature_comment = false;

const sql = prqljs.compile(`from employees | take 10`, opts);
console.log(sql);

Template literal

const prqljs = require("prql-js");
const prql = (string) => prqljs.compile(string[0] || "");

const sql = prql`from employees | select first_name`;
console.log(sql);

Template literal with newlines

const prqljs = require("prql-js");
const prql = (string) => prqljs.compile(string[0] || "");

const sql = prql`
    from employees
    select first_name
`;
console.log(sql);

From a browser

From a framework or a bundler

import compile from "prql-js/dist/bundler";

const sql = compile(`from employees | select first_name`);
console.log(sql);

Errors

Errors are returned as following object, serialized as a JSON array:

interface ErrorMessage {
  /// Message kind. Currently only Error is implemented.
  kind: "Error" | "Warning" | "Lint";
  /// Machine-readable identifier of the error
  code: string | null;
  /// Plain text of the error
  reason: string;
  /// A list of suggestions of how to fix the error
  hint: string | null;
  /// Character offset of error origin within a source file
  span: [number, number] | null;

  /// Annotated code, containing cause and hints.
  display: string | null;
  /// Line and column number of error origin within a source file
  location: SourceLocation | null;
}

/// Location within the source file.
/// Tuples contain:
/// - line number (0-based),
/// - column number within that line (0-based),
interface SourceLocation {
  start: [number, number];

  end: [number, number];
}

These errors can be caught as such:

try {
  const sql = prqlJs.compile(`from employees | foo first_name`);
} catch (error) {
  const errorMessages = JSON.parse(error.message).inner;

  console.log(errorMessages[0].display);
  console.log(errorMessages[0].location);
}

Development

Build:

npm run build

This builds Node, bundler and web packages in the dist path.

Test:

npm test

By default the wasm binaries are optimized on each run, even if the underlying code hasn't changed, which can be slow. For a lower-latency dev loop, pass --profile=dev to npm install for a faster, less optimized build.

npm install prql-js --profile=dev

Notes

• This uses wasm-pack to generate bindings[^1].
• We've added an npm layer on top of the usual approach of just using wasm-pack, so we can distribute a single package with targets of node, bundler and no-modules — somewhat inverting the approach recommended by wasm-pack. The build instruction goes in a build script, rather than a pack script.

[^1]: Though we would be very open to other approaches, given wasm-pack does not seem maintained, and we're eliding many of its features to build for three targets. See for more details.