fix: improve error handling

- Do not terminate the process in code, but throw errors
- Return rejected promises

src/checker/checker-nightmare.js

@@ -10,25 +10,25 @@ const winston = require('winston');
 const PATH_TO_AXE = path.join(path.dirname(require.resolve('axe-core')), 'axe.min.js');
 if (!fs.existsSync(PATH_TO_AXE)) {
   winston.verbose(PATH_TO_AXE);
-  process.exit(1);
+  throw new Error('Can’t find aXe');
 }
 
 const PATH_TO_H5O = path.join(path.dirname(require.resolve('h5o')), 'dist/outliner.min.js');
 if (!fs.existsSync(PATH_TO_H5O)) {
   winston.verbose(PATH_TO_H5O);
-  process.exit(1);
+  throw new Error('Can’t find h5o');
 }
 
 const PATH_TO_ACE_AXE = path.join(__dirname, '../scripts/ace-axe.js');
 if (!fs.existsSync(PATH_TO_ACE_AXE)) {
   winston.verbose(PATH_TO_ACE_AXE);
-  process.exit(1);
+  throw new Error('Can’t find ace-axe script');
 }
 
 const PATH_TO_ACE_EXTRACTION = path.join(__dirname, '../scripts/ace-extraction.js');
 if (!fs.existsSync(PATH_TO_ACE_EXTRACTION)) {
   winston.verbose(PATH_TO_ACE_EXTRACTION);
-  process.exit(1);
+  throw new Error('Can’t find ace-extraction script');
 }
 // EMXIF
 

src/cli/cli.js

@@ -4,6 +4,7 @@
 
 const ace = require('../core/ace.js');
 const meow = require('meow');
+const winston = require('winston');
 
 const cli = meow(`
   Usage
@@ -40,6 +41,9 @@ ace(cli.input[0], {
   tmpdir: cli.flags.tempdir,
   verbose: cli.flags.verbose,
   silent: cli.flags.silent,
-  jobId: ''
+  jobId: '',
 })
-.catch(() => process.exit(1));
+.catch((err) => {
+  winston.error(err.message);
+  process.exit(1);
+});

src/core/ace.js

@@ -22,7 +22,7 @@ module.exports = function ace(epubPath, options) {
     // Check that the EPUB exists
     if (!fs.existsSync(epubPath)) {
       winston.error(`Couldn’t find EPUB file '${epubPath}'`);
-      reject(jobId);
+      return reject(jobId);
     }
 
     // Process options