fix: better logging for errors in js config files (#935)

Before this change javascript config files that had compilation errors or that threw their own errors wouldn't report the error, making debugging a mite more difficult than it should be: instead you'd get a useless "TypeError: Cannot read property 'errors' of undefined" message.  Now if the javascript config file tosses its cookies for whatever reason we can read what that reason was.

Co-authored-by: Ricky Curtice <[email protected]>

lib/index.js

@@ -128,19 +128,24 @@ module.exports = async function lintStaged(
       printTaskOutput(ctx, logger)
       return true
     } catch (runAllError) {
-      const { ctx } = runAllError
-      if (ctx.errors.has(ApplyEmptyCommitError)) {
-        logger.warn(PREVENTED_EMPTY_COMMIT)
-      } else if (ctx.errors.has(GitError) && !ctx.errors.has(GetBackupStashError)) {
-        logger.error(GIT_ERROR)
-        if (ctx.shouldBackup) {
-          // No sense to show this if the backup stash itself is missing.
-          logger.error(RESTORE_STASH_EXAMPLE)
+      if (runAllError && runAllError.ctx && runAllError.ctx.errors) {
+        const { ctx } = runAllError
+        if (ctx.errors.has(ApplyEmptyCommitError)) {
+          logger.warn(PREVENTED_EMPTY_COMMIT)
+        } else if (ctx.errors.has(GitError) && !ctx.errors.has(GetBackupStashError)) {
+          logger.error(GIT_ERROR)
+          if (ctx.shouldBackup) {
+            // No sense to show this if the backup stash itself is missing.
+            logger.error(RESTORE_STASH_EXAMPLE)
+          }
         }
+
+        printTaskOutput(ctx, logger)
+        return false
       }
 
-      printTaskOutput(ctx, logger)
-      return false
+      // Probably a compilation error in the config js file. Pass it up to the outer error handler for logging.
+      throw runAllError
     }
   } catch (lintStagedError) {
     if (lintStagedError === errConfigNotFound) {

test/__snapshots__/index2.spec.js.snap

@@ -0,0 +1,11 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`lintStaged should catch errors from js function config 2`] = `
+"
+ERROR Could not parse lint-staged config.
+
+Error: failed config
+ERROR 
+ERROR Please make sure you have created it correctly.
+See https://github.com/okonet/lint-staged#configuration."
+`;

test/index2.spec.js

@@ -64,4 +64,19 @@ describe('lintStaged', () => {
       }
     `)
   })
+
+  it('should catch errors from js function config', async () => {
+    const logger = makeConsoleMock()
+    const config = {
+      '*': () => {
+        throw new Error('failed config')
+      },
+    }
+
+    expect.assertions(2)
+    await expect(lintStaged({ config }, logger)).rejects.toThrowErrorMatchingInlineSnapshot(
+      `"failed config"`
+    )
+    expect(logger.printHistory()).toMatchSnapshot()
+  })
 })