From 1d902e974654523f390c2741b116ee8995b3f66a Mon Sep 17 00:00:00 2001
From: Eemeli Aro <eemeli@gmail.com>
Date: Sat, 8 Jun 2024 15:16:14 +0300
Subject: [PATCH] fix: Do not allow tab before block collection (fixes #549)

---
 src/compose/resolve-props.ts |  2 +-
 tests/doc/errors.ts          | 23 ++++++++++++++++-------
 2 files changed, 17 insertions(+), 8 deletions(-)

diff --git a/src/compose/resolve-props.ts b/src/compose/resolve-props.ts
index b78b33c6..9a2d1469 100644
--- a/src/compose/resolve-props.ts
+++ b/src/compose/resolve-props.ts
@@ -56,7 +56,7 @@ export function resolveProps(
         if (
           !flow &&
           atNewline &&
-          indicator !== 'doc-start' &&
+          (indicator !== 'doc-start' || next?.type !== 'flow-collection') &&
           token.source[0] === '\t'
         ) {
           tab = token
diff --git a/tests/doc/errors.ts b/tests/doc/errors.ts
index e72439e8..89d7cd7b 100644
--- a/tests/doc/errors.ts
+++ b/tests/doc/errors.ts
@@ -1,13 +1,22 @@
 import * as YAML from 'yaml'
 import { source } from '../_utils'
 
-test('fail on map value indented with tab', () => {
-  const src = 'a:\n\t1\nb:\n\t2\n'
-  const doc = YAML.parseDocument(src)
-  expect(doc.errors).not.toHaveLength(0)
-  expect(() => String(doc)).toThrow(
-    'Document with errors cannot be stringified'
-  )
+describe('tabs as indentation', () => {
+  test('fail on map value indented with tab', () => {
+    const src = 'a:\n\t1\nb:\n\t2\n'
+    const doc = YAML.parseDocument(src)
+    expect(doc.errors[0]).toMatchObject({ code: 'TAB_AS_INDENT' })
+  })
+
+  test('block sequence with leading tab', () => {
+    const doc = YAML.parseDocument('\t- x')
+    expect(doc.errors).toMatchObject([{ code: 'TAB_AS_INDENT' }])
+  })
+
+  test('block map with leading tab', () => {
+    const doc = YAML.parseDocument('\tx: y')
+    expect(doc.errors).toMatchObject([{ code: 'TAB_AS_INDENT' }])
+  })
 })
 
 test('eemeli/yaml#6', () => {