From 52ee29d1beac9f007fbb6ea77344c94417fbfc60 Mon Sep 17 00:00:00 2001
From: leaysgur <6259812+leaysgur@users.noreply.github.com>
Date: Fri, 16 Oct 2026 10:17:38 +0000
Subject: [PATCH] fix(formatter_yaml): never start col-0 line with document
 marker or BOM (#27818)

- Bump `oxc-yaml-parser` to 0.0.7
  - handles NUL as content, BOM only outside a document, markers only at column 0
- Keep `---`/`...` content on the `---` line, keep `?` on a root key starting with a marker, and indent a flow scalar continuation line starting with a marker
- Add `---` before a document whose first text is U+FEFF
---
 Cargo.lock                                    |  4 +-
 Cargo.toml                                    |  2 +-
 crates/oxc_formatter_yaml/AGENTS.md           | 17 +++++
 crates/oxc_formatter_yaml/DIVERGENCES.md      | 51 +++++++++++++
 .../oxc_formatter_yaml/src/print/document.rs  | 28 ++++++-
 .../src/print/mapping_item.rs                 | 14 +++-
 crates/oxc_formatter_yaml/src/print/mod.rs    | 12 +++
 crates/oxc_formatter_yaml/src/print/scalar.rs | 25 +++++--
 .../tests/fixtures/yaml/bom-content.yaml      |  2 +
 .../tests/fixtures/yaml/bom-content.yaml.snap | 21 ++++++
 .../document-marker-content/document.yaml     |  4 +
 .../document.yaml.snap                        | 49 ++++++++++++
 .../yaml/document-marker-content/key.yaml     |  4 +
 .../document-marker-content/key.yaml.snap     | 51 +++++++++++++
 .../yaml/document-marker-content/options.json |  1 +
 .../yaml/document-marker-content/scalar.yaml  |  8 ++
 .../document-marker-content/scalar.yaml.snap  | 74 +++++++++++++++++++
 17 files changed, 355 insertions(+), 12 deletions(-)
 create mode 100644 crates/oxc_formatter_yaml/tests/fixtures/yaml/bom-content.yaml
 create mode 100644 crates/oxc_formatter_yaml/tests/fixtures/yaml/bom-content.yaml.snap
 create mode 100644 crates/oxc_formatter_yaml/tests/fixtures/yaml/document-marker-content/document.yaml
 create mode 100644 crates/oxc_formatter_yaml/tests/fixtures/yaml/document-marker-content/document.yaml.snap
 create mode 100644 crates/oxc_formatter_yaml/tests/fixtures/yaml/document-marker-content/key.yaml
 create mode 100644 crates/oxc_formatter_yaml/tests/fixtures/yaml/document-marker-content/key.yaml.snap
 create mode 100644 crates/oxc_formatter_yaml/tests/fixtures/yaml/document-marker-content/options.json
 create mode 100644 crates/oxc_formatter_yaml/tests/fixtures/yaml/document-marker-content/scalar.yaml
 create mode 100644 crates/oxc_formatter_yaml/tests/fixtures/yaml/document-marker-content/scalar.yaml.snap

diff --git a/Cargo.lock b/Cargo.lock
index be235aa7e5..8999d1fd97 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1734,9 +1734,9 @@ checksum = "f321c22ccee109a6fe0aef08d1521af693e4b178dcb7259137ff08f8ce5388d8"
 
 [[package]]
 name = "oxc-yaml-parser"
-version = "0.0.6"
+version = "0.0.7"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "097919ec3fb73bb7ec22ceea30171c0af1f14fa67d03bd410a15dc3b6b8eff1b"
+checksum = "41ca5cfdf8b83491f53dd1fe583f43923100eacf76d3b8e6bce9d24dec93356c"
 dependencies = [
  "oxc_allocator",
 ]
diff --git a/Cargo.toml b/Cargo.toml
index 3362e57902..6a73cc3c53 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -244,7 +244,7 @@ oxc-css-parser = "0.0.17" # CSS/SCSS/Less parser (raffia 0.12.3 fork: adds `temp
 oxc-graphql-parser = "0.0.9" # GraphQL parser (direct AST; apollo-parser 0.8.6 fork aligned with graphql-js 17 syntax)
 oxc-markdown-parser = "0.0.3" # CommonMark + GFM parser (span-faithful, style-preserving typed AST)
 oxc-toml = "0.15.1" # TOML parser and formatter
-oxc-yaml-parser = "0.0.6" # YAML 1.2 parser (comment-preserving typed AST, node naming from `yaml-unist-parser`)
+oxc-yaml-parser = "0.0.7" # YAML 1.2 parser (comment-preserving typed AST, node naming from `yaml-unist-parser`)
 papaya = "0.2.4" # Concurrent hash map
 percent-encoding = "2.3.2" # URL encoding
 petgraph = { version = "0.8.3", default-features = false } # Graph data structures
diff --git a/crates/oxc_formatter_yaml/AGENTS.md b/crates/oxc_formatter_yaml/AGENTS.md
index 64a2c61742..d5c2d0e995 100644
--- a/crates/oxc_formatter_yaml/AGENTS.md
+++ b/crates/oxc_formatter_yaml/AGENTS.md
@@ -36,6 +36,23 @@ The printer re-emits the configured `end_of_line` at the final stage.
 
 A leading BOM is stripped before parsing and re-emitted by `format()`.
 
+### Line starts
+
+A line the printer starts at column 0 must not read back as stream-level syntax (see the parser README "Input acceptance"):
+
+- `---`/`...` followed by a blank or the end is a document marker
+- U+FEFF outside a document is a BOM
+
+Column 0 is reached at these sites, each guarded without changing the value:
+
+- The document's first text (`print/document.rs`): content after `---` stays on its line; a document without `---` whose first text is U+FEFF gets one
+- A root mapping key (`print/mapping_item.rs`): a key starting with a marker keeps its `?`
+- A flow scalar's continuation line outside block collections (`print/scalar.rs`): a line starting with a marker is indented
+  - This also covers entries of a root flow collection, already indented, where the extra indent is harmless
+
+Elsewhere lines start at column 2 or more and Prettier's layout is matched.
+See DIVERGENCES.md#document-marker-content and DIVERGENCES.md#bom-content.
+
 ### Comments
 
 Positional cursor (`Comments` in `src/comments.rs`), same approach as graphql/json, yaml-unist-parser's attach algorithm is NOT ported.
diff --git a/crates/oxc_formatter_yaml/DIVERGENCES.md b/crates/oxc_formatter_yaml/DIVERGENCES.md
index be784fd8b4..569bfe5a02 100644
--- a/crates/oxc_formatter_yaml/DIVERGENCES.md
+++ b/crates/oxc_formatter_yaml/DIVERGENCES.md
@@ -293,3 +293,54 @@ run:
 A same-line trailing comment never counts toward the `fits` measurement, the treatment Prettier itself gives JS/JSON line comments and YAML flow collections, but not the block scalar header.
 Same rule as CSS `trailing-line-comment-print-width`.
 The KEY does count: a long key overflowing on `key: |` alone breaks the pair exactly like Prettier.
+
+## document-marker-content
+
+- Why: semantics
+- Pin: `tests/fixtures/yaml/document-marker-content/document.yaml`, `tests/fixtures/yaml/document-marker-content/key.yaml`, `tests/fixtures/yaml/document-marker-content/scalar.yaml`
+
+```yaml
+# input
+--- ---
+? --- x
+: m
+# (proseWrap: always, printWidth: 10)
+aaaa bbbb --- cccc
+
+# ours: no line starts with the marker at column 0
+--- ---
+? --- x
+: m
+aaaa bbbb
+  --- cccc
+
+# prettier: the content becomes a marker
+---
+---
+--- x: m
+aaaa bbbb
+--- cccc
+```
+
+Text starting with `---` or `...` never starts a line at column 0, where it is read as a document marker (`"---"` becomes an empty document, the rest fails to parse).
+The guarded sites are listed in AGENTS.md "Line starts".
+
+## bom-content
+
+- Why: semantics
+- Pin: `tests/fixtures/yaml/bom-content.yaml`
+
+```yaml
+# input ("␢" marks U+FEFF)
+? ␢a
+: m
+
+# ours: a `---` keeps the key inside a document
+---
+␢a: m
+
+# prettier: the key leads the stream, read back as a BOM, the key becomes "a"
+␢a: m
+```
+
+A U+FEFF never starts the text of a document without `---`, where it is read as a BOM: the document gets a `---` (AGENTS.md "Line starts").
diff --git a/crates/oxc_formatter_yaml/src/print/document.rs b/crates/oxc_formatter_yaml/src/print/document.rs
index 85b0cba893..dbdb343965 100644
--- a/crates/oxc_formatter_yaml/src/print/document.rs
+++ b/crates/oxc_formatter_yaml/src/print/document.rs
@@ -2,7 +2,7 @@ use oxc_formatter_core::{
     builders::{hard_line_break, space, text},
     write,
 };
-use oxc_yaml_parser::ast::{Directive, Document, Root};
+use oxc_yaml_parser::ast::{Content, Directive, Document, Node, Root};
 
 use crate::{
     comments::{
@@ -13,7 +13,7 @@ use crate::{
     print::{
         YamlFormatter,
         block::{ends_with_keep_chomped_block, item_gap_anchor, last_descendant_block_scalar},
-        to_span, write_node_or_suppressed,
+        source_starts_with_document_marker, to_span, write_node_or_suppressed,
     },
 };
 
@@ -137,6 +137,20 @@ fn write_document<'a>(document: &'a Document<'a>, f: &mut YamlFormatter<'_, 'a>)
     }
 
     if let Some(node) = &document.body.content {
+        let source = f.context().source_text();
+        if let Some(marker) = document.directives_end_marker {
+            // Content starting with `---`/`...` stays on the `---` line: on a line of its own it would become a marker
+            if source.all_bytes_match(marker.end, node.span.start, |b| matches!(b, b' ' | b'\t'))
+                && source_starts_with_document_marker(node.span.start, f)
+            {
+                needs_line = false;
+                write!(f, space());
+            }
+        } else if source.as_str()[first_key_start(node) as usize..].starts_with('\u{FEFF}') {
+            // Content starting with U+FEFF needs a `---`: outside a document it would be read as a BOM
+            write!(f, "---");
+            needs_line = true;
+        }
         if needs_line {
             write!(f, hard_line_break());
         }
@@ -156,6 +170,16 @@ fn write_document<'a>(document: &'a Document<'a>, f: &mut YamlFormatter<'_, 'a>)
     }
 }
 
+/// Where a block mapping's first key starts: a one-line explicit key loses its `?` (`print/mapping_item.rs`),
+/// so the key text may lead the output.
+fn first_key_start(node: &Node<'_>) -> u32 {
+    let key = match &node.content {
+        Content::Mapping(mapping) => mapping.children.first().and_then(|item| item.key_content()),
+        _ => None,
+    };
+    key.map_or(node.span.start, |key| key.span.start)
+}
+
 /// Re-joins directive words with single spaces (whitespace runs between them are normalized).
 fn write_directive<'a>(directive: &'a Directive<'a>, f: &mut YamlFormatter<'_, 'a>) {
     write!(f, "%");
diff --git a/crates/oxc_formatter_yaml/src/print/mapping_item.rs b/crates/oxc_formatter_yaml/src/print/mapping_item.rs
index 0962bbe338..b753ab1636 100644
--- a/crates/oxc_formatter_yaml/src/print/mapping_item.rs
+++ b/crates/oxc_formatter_yaml/src/print/mapping_item.rs
@@ -14,7 +14,10 @@ use crate::{
     },
     context::YamlFormatContext,
     options::ProseWrap,
-    print::{YamlFormatter, column_of, format_with, to_span, write_node, write_node_or_suppressed},
+    print::{
+        YamlFormatter, column_of, format_with, source_starts_with_document_marker, to_span,
+        write_node, write_node_or_suppressed,
+    },
 };
 
 /// Where a mapping item lives; decides the empty-value layout
@@ -61,6 +64,10 @@ pub fn write_mapping_item<'a>(
     }
 
     let space_before_colon = key_content.is_some_and(|k| matches!(k.content, Content::Alias(_)));
+    // A root mapping key starting with a document marker keeps its `?`: without it the key starts a line at column 0
+    let key_starts_with_marker = in_flow == FlowParent::No
+        && f.context().collection_depth().get() == 1
+        && key_content.is_some_and(|k| source_starts_with_document_marker(k.span.start, f));
 
     if is_empty_value {
         if in_flow == FlowParent::Mapping {
@@ -79,6 +86,7 @@ pub fn write_mapping_item<'a>(
             && is_absolutely_single_line(key_content, f)
             && !parent_tag_is_set
             && !key_content_trailing_comment
+            && !key_starts_with_marker
         {
             write_key(item, f);
             if space_before_colon {
@@ -106,12 +114,14 @@ pub fn write_mapping_item<'a>(
     let value_start = value_node.span.start;
 
     // Force explicit key:
-    // the key isn't an inline node, or the source was already explicit with a comment between `?` and the key,
+    // the key isn't an inline node or starts with a document marker,
+    // or the source was already explicit with a comment between `?` and the key,
     // or between the key and `:` (an implicit `key:` with a comment above the value keeps the implicit form,
     // the comment becomes the value's leading comment instead).
     let explicit_comment_before_key = key.explicit
         && f.context().comments().peek().is_some_and(|c| c.span.end <= key_node.span.start);
     if !is_inline(key_content)
+        || key_starts_with_marker
         || explicit_comment_before_key
         || (key.explicit && has_own_line_comment_before_value(value_node, f))
     {
diff --git a/crates/oxc_formatter_yaml/src/print/mod.rs b/crates/oxc_formatter_yaml/src/print/mod.rs
index dc5860ec2d..1288c4170a 100644
--- a/crates/oxc_formatter_yaml/src/print/mod.rs
+++ b/crates/oxc_formatter_yaml/src/print/mod.rs
@@ -59,6 +59,18 @@ pub fn column_of(source: &str, offset: u32) -> u32 {
     u32::try_from(count).unwrap_or(u32::MAX)
 }
 
+/// Whether `text` starts with a document marker: `---`/`...` followed by a blank or the end.
+/// At column 0 it would be read as one, see AGENTS.md "Line starts".
+pub fn starts_with_document_marker(text: &str) -> bool {
+    (text.starts_with("---") || text.starts_with("..."))
+        && text.as_bytes().get(3).is_none_or(|b| matches!(b, b' ' | b'\t' | b'\n'))
+}
+
+/// [starts_with_document_marker] for the source text from `offset`.
+pub fn source_starts_with_document_marker(offset: u32, f: &YamlFormatter<'_, '_>) -> bool {
+    starts_with_document_marker(&f.context().source_text().as_str()[offset as usize..])
+}
+
 /// Emits a node's properties (anchor/tag) in their source order.
 /// NOTE: Prettier 3.9.5 normalizes to `tag anchor` order; we keep the source order instead.
 ///
diff --git a/crates/oxc_formatter_yaml/src/print/scalar.rs b/crates/oxc_formatter_yaml/src/print/scalar.rs
index 30e68fc1c8..7e0f295b3f 100644
--- a/crates/oxc_formatter_yaml/src/print/scalar.rs
+++ b/crates/oxc_formatter_yaml/src/print/scalar.rs
@@ -4,12 +4,15 @@ use cow_utils::CowUtils;
 
 use oxc_formatter_core::{
     arena_cow_str,
-    builders::{exact_line_breaks, hard_line_break, soft_line_break_or_space, text},
+    builders::{Line, exact_line_breaks, hard_line_break, indent, soft_line_break_or_space, text},
     write,
 };
 use oxc_span::Span;
 
-use crate::{options::ProseWrap, print::YamlFormatter};
+use crate::{
+    options::ProseWrap,
+    print::{YamlFormatter, format_with, starts_with_document_marker},
+};
 
 /// Which flow scalar shape is being folded (affects word-merge rules and quoting).
 #[derive(Clone, Copy, Eq, PartialEq)]
@@ -117,6 +120,18 @@ pub fn write_flow_scalar_content<'a>(
         })
         .collect();
 
+    // Outside block collections, continuation lines start at column 0:
+    // a line starting with a document marker is indented instead (see AGENTS.md "Line starts")
+    let guards_line_start = f.context().collection_depth().get() == 0;
+    let line_before = |line: Line, word: &'a str| {
+        format_with(move |f| {
+            if guards_line_start && starts_with_document_marker(word) {
+                write!(f, indent(&line));
+            } else {
+                write!(f, line);
+            }
+        })
+    };
     let mut blanks = 0usize;
     let mut wrote_any = false;
     for words in &line_groups {
@@ -127,15 +142,15 @@ pub fn write_flow_scalar_content<'a>(
         if blanks > 0 {
             // N blank groups = N separators before this group
             // (plus the one separating it from the previous non-empty group, if any).
-            write!(f, exact_line_breaks(blanks + usize::from(wrote_any)));
+            write!(f, line_before(exact_line_breaks(blanks + usize::from(wrote_any)), words[0]));
         } else if wrote_any {
-            write!(f, hard_line_break());
+            write!(f, line_before(hard_line_break(), words[0]));
         }
         blanks = 0;
         wrote_any = true;
         let mut fill = f.fill();
         for &word in words {
-            fill.entry(&soft_line_break_or_space(), &text(word));
+            fill.entry(&line_before(soft_line_break_or_space(), word), &text(word));
         }
         fill.finish();
     }
diff --git a/crates/oxc_formatter_yaml/tests/fixtures/yaml/bom-content.yaml b/crates/oxc_formatter_yaml/tests/fixtures/yaml/bom-content.yaml
new file mode 100644
index 0000000000..062f199152
--- /dev/null
+++ b/crates/oxc_formatter_yaml/tests/fixtures/yaml/bom-content.yaml
@@ -0,0 +1,2 @@
+? a
+: m
diff --git a/crates/oxc_formatter_yaml/tests/fixtures/yaml/bom-content.yaml.snap b/crates/oxc_formatter_yaml/tests/fixtures/yaml/bom-content.yaml.snap
new file mode 100644
index 0000000000..43dbabfbcf
--- /dev/null
+++ b/crates/oxc_formatter_yaml/tests/fixtures/yaml/bom-content.yaml.snap
@@ -0,0 +1,21 @@
+---
+source: crates/oxc_formatter_yaml/tests/fixtures/mod.rs
+---
+==================== Input ====================
+? a
+: m
+
+==================== Output ====================
+------------------
+{ printWidth: 80 }
+------------------
+---
+a: m
+
+-------------------
+{ printWidth: 100 }
+-------------------
+---
+a: m
+
+===================== End =====================
diff --git a/crates/oxc_formatter_yaml/tests/fixtures/yaml/document-marker-content/document.yaml b/crates/oxc_formatter_yaml/tests/fixtures/yaml/document-marker-content/document.yaml
new file mode 100644
index 0000000000..4b17f98bf2
--- /dev/null
+++ b/crates/oxc_formatter_yaml/tests/fixtures/yaml/document-marker-content/document.yaml
@@ -0,0 +1,4 @@
+--- ---
+--- ... x
+--- --- a
+  b
diff --git a/crates/oxc_formatter_yaml/tests/fixtures/yaml/document-marker-content/document.yaml.snap b/crates/oxc_formatter_yaml/tests/fixtures/yaml/document-marker-content/document.yaml.snap
new file mode 100644
index 0000000000..53c9b4dce0
--- /dev/null
+++ b/crates/oxc_formatter_yaml/tests/fixtures/yaml/document-marker-content/document.yaml.snap
@@ -0,0 +1,49 @@
+---
+source: crates/oxc_formatter_yaml/tests/fixtures/mod.rs
+---
+==================== Input ====================
+--- ---
+--- ... x
+--- --- a
+  b
+
+==================== Output ====================
+------------------
+{ printWidth: 80 }
+------------------
+--- ---
+--- ... x
+--- --- a
+b
+
+-------------------
+{ printWidth: 100 }
+-------------------
+--- ---
+--- ... x
+--- --- a
+b
+
+---------------------------------------
+{ printWidth: 10, proseWrap: "always" }
+---------------------------------------
+--- ---
+--- ... x
+--- --- a
+b
+
+---------------------------------------
+{ printWidth: 80, proseWrap: "always" }
+---------------------------------------
+--- ---
+--- ... x
+--- --- a b
+
+----------------------------------------
+{ printWidth: 100, proseWrap: "always" }
+----------------------------------------
+--- ---
+--- ... x
+--- --- a b
+
+===================== End =====================
diff --git a/crates/oxc_formatter_yaml/tests/fixtures/yaml/document-marker-content/key.yaml b/crates/oxc_formatter_yaml/tests/fixtures/yaml/document-marker-content/key.yaml
new file mode 100644
index 0000000000..f737daff29
--- /dev/null
+++ b/crates/oxc_formatter_yaml/tests/fixtures/yaml/document-marker-content/key.yaml
@@ -0,0 +1,4 @@
+a: 1
+? --- x
+: m
+? ... y
diff --git a/crates/oxc_formatter_yaml/tests/fixtures/yaml/document-marker-content/key.yaml.snap b/crates/oxc_formatter_yaml/tests/fixtures/yaml/document-marker-content/key.yaml.snap
new file mode 100644
index 0000000000..c64d53e259
--- /dev/null
+++ b/crates/oxc_formatter_yaml/tests/fixtures/yaml/document-marker-content/key.yaml.snap
@@ -0,0 +1,51 @@
+---
+source: crates/oxc_formatter_yaml/tests/fixtures/mod.rs
+---
+==================== Input ====================
+a: 1
+? --- x
+: m
+? ... y
+
+==================== Output ====================
+------------------
+{ printWidth: 80 }
+------------------
+a: 1
+? --- x
+: m
+? ... y
+
+-------------------
+{ printWidth: 100 }
+-------------------
+a: 1
+? --- x
+: m
+? ... y
+
+---------------------------------------
+{ printWidth: 10, proseWrap: "always" }
+---------------------------------------
+a: 1
+? --- x
+: m
+? ... y
+
+---------------------------------------
+{ printWidth: 80, proseWrap: "always" }
+---------------------------------------
+a: 1
+? --- x
+: m
+? ... y
+
+----------------------------------------
+{ printWidth: 100, proseWrap: "always" }
+----------------------------------------
+a: 1
+? --- x
+: m
+? ... y
+
+===================== End =====================
diff --git a/crates/oxc_formatter_yaml/tests/fixtures/yaml/document-marker-content/options.json b/crates/oxc_formatter_yaml/tests/fixtures/yaml/document-marker-content/options.json
new file mode 100644
index 0000000000..ffb985f4ac
--- /dev/null
+++ b/crates/oxc_formatter_yaml/tests/fixtures/yaml/document-marker-content/options.json
@@ -0,0 +1 @@
+[{}, { "proseWrap": "always", "printWidth": 10 }]
diff --git a/crates/oxc_formatter_yaml/tests/fixtures/yaml/document-marker-content/scalar.yaml b/crates/oxc_formatter_yaml/tests/fixtures/yaml/document-marker-content/scalar.yaml
new file mode 100644
index 0000000000..bfa712bb32
--- /dev/null
+++ b/crates/oxc_formatter_yaml/tests/fixtures/yaml/document-marker-content/scalar.yaml
@@ -0,0 +1,8 @@
+aaaa bbbb --- cccc
+---
+"aaaa
+  --- x"
+---
+aaaa
+
+  ... x
diff --git a/crates/oxc_formatter_yaml/tests/fixtures/yaml/document-marker-content/scalar.yaml.snap b/crates/oxc_formatter_yaml/tests/fixtures/yaml/document-marker-content/scalar.yaml.snap
new file mode 100644
index 0000000000..e991d2edcf
--- /dev/null
+++ b/crates/oxc_formatter_yaml/tests/fixtures/yaml/document-marker-content/scalar.yaml.snap
@@ -0,0 +1,74 @@
+---
+source: crates/oxc_formatter_yaml/tests/fixtures/mod.rs
+---
+==================== Input ====================
+aaaa bbbb --- cccc
+---
+"aaaa
+  --- x"
+---
+aaaa
+
+  ... x
+
+==================== Output ====================
+------------------
+{ printWidth: 80 }
+------------------
+aaaa bbbb --- cccc
+---
+"aaaa
+  --- x"
+---
+aaaa
+
+  ... x
+
+-------------------
+{ printWidth: 100 }
+-------------------
+aaaa bbbb --- cccc
+---
+"aaaa
+  --- x"
+---
+aaaa
+
+  ... x
+
+---------------------------------------
+{ printWidth: 10, proseWrap: "always" }
+---------------------------------------
+aaaa bbbb
+  --- cccc
+---
+"aaaa ---
+x"
+---
+aaaa
+
+  ... x
+
+---------------------------------------
+{ printWidth: 80, proseWrap: "always" }
+---------------------------------------
+aaaa bbbb --- cccc
+---
+"aaaa --- x"
+---
+aaaa
+
+  ... x
+
+----------------------------------------
+{ printWidth: 100, proseWrap: "always" }
+----------------------------------------
+aaaa bbbb --- cccc
+---
+"aaaa --- x"
+---
+aaaa
+
+  ... x
+
+===================== End =====================