check-coverage

#!/usr/bin/node
'use strict';
/* eslint-disable no-console */

const fs = require('fs');
const { execFileSync } = require('child_process');

const coverage_file = process.argv[2];
const new_coverage = JSON.parse(
  fs.readFileSync(coverage_file, { encoding: 'utf8' }),
);

let prev_coverage_ref;
if (Object.prototype.hasOwnProperty.call(process.env, 'PRE_COMMIT_FROM_REF')) {
  prev_coverage_ref = process.env.PRE_COMMIT_FROM_REF;
} else {
  prev_coverage_ref = 'HEAD';
}
let prev_coverage_text;
try {
  prev_coverage_text = execFileSync(
    'git',
    ['show', `${prev_coverage_ref}:${coverage_file}`],
    { encoding: 'utf8' },
  );
} catch (e) {
  console.log('Previous coverage is not found');
  prev_coverage_text = '{}';
}
const prev_coverage = JSON.parse(prev_coverage_text);

let decreased = false;
Object.keys(new_coverage).forEach((f) => {
  if (f === 'total') {
    return;
  }
  Object.keys(new_coverage[f])
    .sort()
    .forEach((what) => {
      let prev_val = 0;
      if (f in prev_coverage) {
        prev_val = parseFloat(prev_coverage[f][what].pct);
      }
      const new_val = parseFloat(new_coverage[f][what].pct);
      if (new_val < prev_val) {
        decreased = true;
        console.log(`${f} ${what}: ${prev_val} -> ${new_val}`);
      }
    });
});
if (decreased) {
  process.exit(2);
}