preval/src/index.mjs

Wannabe compiler tool for JS

import { clearStdio, setStdio, log, group, groupEnd } from './utils.mjs';
import { phase0 } from './phase0.mjs';
import { phase1 } from './phase1.mjs';
import { phase2 } from './phase2.mjs';
import { printer } from '../lib/printer.mjs';

export function preval({ entryPointFile, stdio, resolve, req }) {
  if (stdio) setStdio(stdio);
  else clearStdio();

  const code = req(entryPointFile);
  const fdata = phase0(code, entryPointFile);
  const program = {
    modules: new Map([[fdata.name, fdata]]),
    main: fdata.name,
  };
  phase1(program, fdata, resolve, req);
  phase2(program, fdata, resolve, req);

  fdata.globallyUniqueNamingRegistery.forEach((obj, uniqueName) => {
    console.log('-', uniqueName, obj);
    if (obj.updates.length === 1) {
      let update = obj.updates[0].parent[obj.updates[0].prop];
      if (obj.updates[0].index >= 0) update = update[obj.updates[0].index];
      if (update.type === 'Literal') {
        log('Replacing literal binding with the literal...');

        // Replace all occurrences with the literal...
        obj.usages.forEach(({parent, prop, index}) => {
          // Cannot replace the declaration itself. But can eliminate it
          if (parent.type === 'VariableDeclarator' && prop !== 'init') {
            // TODO: Eliminate this declaration...
            log('TODO: eliminate var declarator');

          } else {
            log('Replacing a usage of `' + uniqueName + '` with a literal');
            if (index >= 0) parent[prop][index] = update;
            else parent[prop] = update;
          }
        });
      }
    }
  })

  // This is where the magic starts

  return {
    files: {
      // note: test runner will auto-Prettier the result. Perhaps this should be done here..? Or let the user take care of that?
      [entryPointFile]: printer(fdata.tenkoOutput.ast),
    },
  };
}