Test that the berry stanza view and block scan agree

The hosted berry writers read the lock as blank-line stanzas and the
vendored backend and field readers through scan_blocks. A test now
asserts both name the same blocks in the same order across LF, CRLF,
BOM, header-comment and no-trailing-newline locks, so the two reads
cannot drift on any shape yarn writes.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

Author: mikolalysenko

crates/socket-patch-core/src/formats/yarn/stanzas.rs

@@ -173,4 +173,43 @@ mod tests {
         assert_eq!(stanza_key("# yarn lockfile"), None);
         assert_eq!(stanza_key("  version: 8"), None);
     }
+
+    /// The stanza view and [`super::super::blocks::scan_blocks`] are two
+    /// reads of one berry lock (the hosted writers use the first, the
+    /// vendored backend and the field readers the second): on every shape
+    /// yarn writes — LF, CRLF, a BOM, a header comment, sub-maps, a final
+    /// entry with or without a trailing newline — they must name the same
+    /// blocks in the same order. (A blank line inside a block, which yarn
+    /// never writes, is where they would part.)
+    #[test]
+    fn stanza_keys_match_the_block_scan_on_every_line_ending() {
+        use super::super::blocks::scan_blocks;
+        let lf = "# This file is generated by running \"yarn install\" inside your project.\n\
+                  # Manual changes might be lost - proceed with caution!\n\n\
+                  __metadata:\n  version: 8\n  cacheKey: 10c0\n\n\
+                  \"@scope/a@npm:^1.0.0, @scope/a@npm:^1.2.0\":\n  version: 1.2.0\n  \
+                  resolution: \"@scope/a@npm:1.2.0\"\n  dependencies:\n    b: \"npm:^2\"\n  \
+                  checksum: 10c0/aa\n  languageName: node\n  linkType: hard\n\n\
+                  \"app@workspace:.\":\n  version: 0.0.0-use.local\n  resolution: \"app@workspace:.\"\n\n\
+                  \"b@npm:^2\":\n  version: 2.0.0\n  resolution: \"b@npm:2.0.0\"\n  bin:\n    b: cli.js\n";
+        let crlf = lf.replace('\n', "\r\n");
+        for text in [
+            lf.to_string(),
+            lf.trim_end().to_string(),
+            crlf.clone(),
+            format!("\u{feff}{crlf}"),
+            format!("\u{feff}{lf}\n\n"),
+        ] {
+            let stanzas = BerryStanzas::parse(&text);
+            let from_stanzas: Vec<&str> = stanzas
+                .stanzas
+                .iter()
+                .filter_map(|s| stanza_key(s))
+                .collect();
+            let blocks = scan_blocks(&text);
+            let from_blocks: Vec<&str> = blocks.iter().map(|b| b.key.as_str()).collect();
+            assert_eq!(from_stanzas, from_blocks, "{text:?}");
+            assert_eq!(from_blocks.len(), 4, "{text:?}");
+        }
+    }
 }