REPL: import statement inside the Node.js REPL

[hemanth]

What is the problem this feature will solve?

Allow import statements in REPL

What is the feature you are proposing to solve the problem?

Instead of:

> import assert from 'node:assert'
import assert from 'node:assert'
^^^^^^

Uncaught:
SyntaxError: Cannot use import statement inside the Node.js REPL, alternatively use dynamic import

Can we convert them to dynamic import and execute? Just in the REPL.

Like how top level await was supported in Chrome before TLA was an accepted TC39 proposal.

What alternatives have you considered?

At the least we change the message.

from:

Uncaught:
SyntaxError: Cannot use import statement inside the Node.js REPL, alternatively use dynamic import

to:

Uncaught:
SyntaxError: Cannot use import statement inside the Node.js REPL, alternatively use dynamic import

Instead of:
  import assert from 'node: assert'

use:
 const assert = await import('node: assert')

[aduh95]

Static imports are valid syntax only at the top-level body of a module, so that wouldn't be suited for REPL IIUC.

Like how top level await was supported in Chrome before TLA was an accepted TC39 proposal.

It should be noted that Chrome DevTools still don't let you use static imports in its console.

At the least we change the message.

That sounds like a more reasonable proposal, would you like to submit a PR?

[hemanth]

Sure @aduh95 I can do a PR for this.

[hemanth]

@aduh95 Wondering if we should handle all variations of static imports and convert that to dynamic imports or just show a generic example! 🤷

[aduh95]

There are three types on static import, you don’t have to treat them all the same. If you can show the actual replacement for the user, that’s of course more valuable, but if that’s too difficult it’s ok to use a generic example.

[hemanth]

These four types should be good?

Named import: import { export1, export2 } from "module-name";
Default import: import defaultExport from "module-name";
Namespace import: import * as name from "module-name";
Side effect import: import "module-name";

But then, do we have AST capabilities baked in the source to covert this or do we depend on a robust RE?

[aduh95]

We have acorn

[hemanth]

Added a sample to acron explorer.

import * as name from "module-name"; gets interesting.

[hemanth]

@aduh95 It was easier than expected with acron, not clear on how to import the dep acorn and acorn-walk in repl.js though.

const toDynamicImport = (codeLine) => {
  let dynamicImportStatement = ''
  const ast = acorn.parse(codeSnippet, { sourceType: 'module' });

  walk.ancestor(ast, {
    ImportDeclaration(node, ancestors) {
      const importedModules = node.source.value;
      let importedSpecifiers = node.specifiers.map(specifier => specifier.local.name);

      if (importedSpecifiers.length > 1) {
        importedSpecifiers = `{${importedSpecifiers.join(" ")}}`
      }
      dynamicImportStatement = `const ${importedSpecifiers} = await import('${importedModules}')`;
    },
  });
  return dynamicImportStatement;
} 

self.lines.at(-2) at repl.js#694 will give us the static import lines that the user inputted.

[aduh95]

not clear on how to import the dep acorn and acorn-walk in repl.js though.

We already import it:

node/lib/repl.js

Lines 104 to 107 in 05693ac

	const {
	isIdentifierStart,
	isIdentifierChar,
	} = require('internal/deps/acorn/acorn/dist/acorn');

[hemanth]

Ah, no wonder, it didn't show up for me in search :D