ANN vitest-bdd: ReScript testing with vitest (and source maps !)

The full sources of the “compiler” is here.

The basic idea is that I parse each lines of the original rescript code and the compiled code looking for corresponding tests. It is done in a way that multiple tests can have the same string.

const TEST_RE = /(describe|it|test|only|skip|todo)\(("([^"]*)")/;

And then I interploate corresponding line numbers between the two files:

const map = new SourceMapGenerator({ file: path });

// rescript line, compiled line
function sm(rline: number, cline: number) {
  map.addMapping({
    source: path,
    generated: { line: cline, column: 0 },
    original: { line: rline, column: 0 },
  });
}
let ri = 1;
let ci = 1;

for (const [rline, cline] of smap) {
  let dr = rline - ri;
  let dc = cline - ci;
  if (dr > dc) {
    for (let i = 1; i <= dr; i++) {
      sm(ri + i, Math.ceil(ci + (i * dc) / dr));
    }
  } else {
    for (let i = 1; i <= dc; i++) {
      sm(Math.ceil(ri + (i * dr) / dc), ci + i);
    }
  }
  ri = rline;
  ci = cline;
}

The smap array is built by first parsing rescript and then matching the lines in the compiled source.

At the end, I send the compiled JS sources with the source maps to vitest.