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Version: Next (unreleased)

Modules

xisto uses ES modules. The whole program is compiled together, and functions nobody calls are left out of the executable, so importing a large module costs only what you use.

Imports and exports​

FormSupported
import { a, b } from "./x.ts", import type, import { type T, v }yes
import * as ns from "./x.ts"yes
const lib = require("./x.ts") at the top levelyes, read as import * as
export * from, export { a } from, export { a as b } from (barrels)yes
export * as ns fromno (XS1039)
an import after other declarationsyes
import "./x.ts" for its side effectscompiles, but the module's top-level code does not run
import { twice, NAME } from "./lib/index.ts";   // a barrel: export * from "./a.ts"
import * as lib from "./lib/a.ts";
import { Box } from "@util/b";                  // tsconfig paths

tsconfig paths​

compilerOptions.paths and baseUrl from tsconfig.json are honoured, including through extends.

xisto: and node:​

xisto's own implementations of Node's modules are imported with the xisto: prefix: xisto:fs, xisto:timers/promises, xisto:child_process… Importing node:fs, or the bare fs, is refused by default, because it is not Node itself:

x.ts:1:1: error[XS4001]: 'node:timers/promises' is xisto's implementation of a Node module, not Node itself
  help: import it as "xisto:timers/promises", or build with --node-compat (XISTO_NODE_COMPAT=1) to keep the Node name

With --node-compat (or XISTO_NODE_COMPAT=1) the Node names are accepted as written, so the same source runs on Node and on xisto. See Node compatibility.

Packages​

A bare name (import { hi } from "greet") is resolved in this order:

  1. relative paths;
  2. tsconfig.json paths;
  3. the directory in XISTO_PKGS (or --pkgs DIR);
  4. .xisto/pkgs/<name> in the nearest ancestor directory; the entry is main in its xisto.json, else index.ts or src/index.ts.

A name that resolves nowhere is an error:

error[XS5003]: cannot resolve 'nothere'
  help: import files with a relative path ("./file"), or add the package: xisto add nothere

Warnings inside package files are not reported. See Projects and packages.

Circular imports​

Circular imports compile. Functions that call each other across modules work as on Node. A top-level value read by another module before its own module ran is a ReferenceError on Node; do not rely on the order xisto initializes such values in.

See also​