fix(parsing): allow a directive after a document-end marker

A directive following a document-end marker ('...') begins the next
document's directive section, but the scanner rejected it: the
isDocumentClosed flag set by '...' tripped the directive guard, so a
multi-document stream where each document carries its own directives
('%TAG ...' / '--- doc' / '...' / '%TAG ...' / '--- doc') failed.

A directive now reopens the stream when it follows '...', clearing the
closed flag, while a directive after document content within the same
document stays rejected via the content guard. The directive still
requires its own '---', so a directive after '...' with no document start
is still an error. Multi-document streams already composed through the
stream mode; this removes the scanner-side block on per-document
directives.

Measured against the official YAML test-suite, parse-level conformance
rises from 278/333 (83.5%) to 283/333 (85.0%) with no regression.

CHANGELOG.md

@@ -23,6 +23,13 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Fixed
 
+- A directive after a document-end marker (`...`) now begins the next document instead of being
+  rejected. A multi-document stream where each document carries its own directives
+  (`%TAG ...` / `--- doc` / `...` / `%TAG ...` / `--- doc`) is now accepted, since a directive
+  following `...` opens the next document's directive section. A directive after document content
+  within the same document is still rejected, and a directive after `...` still requires its own
+  `---`. Lifts official test-suite parse-level conformance from 278/333 (83.5%) to 283/333
+  (85.0%), with no regression.
 - A block sequence entry can no longer follow a flow collection that closed earlier on the same
   line (`- { y: z }- invalid`, `- [a] - b`); the entry would begin a sequence inline after a
   complete node. The scanner now tracks a top-level flow close on the current line and rejects a

Sources/Parsing/Scanner.Directives.swift

@@ -88,7 +88,12 @@ extension PureYAML.Parsing.Scanner {
         guard let name = parts.first else {
             return
         }
-        guard !state.hasDocumentContent, !state.hasDocumentStartMarker, !state.isDocumentClosed else {
+        // A directive after a document-end marker (`...`) begins the next document's directive
+        // section, so it reopens the stream for a new document rather than being rejected.
+        if state.isDocumentClosed {
+            state.isDocumentClosed = false
+        }
+        guard !state.hasDocumentContent, !state.hasDocumentStartMarker else {
             throw PureYAML.Parsing.ParseError.unsupportedDirective(name: name, line: start.line)
         }
         // Every directive must be followed by an explicit `---`; record that one is now awaiting it.

Tests/DirectiveAfterDocumentEndTests.swift

@@ -0,0 +1,28 @@
+@testable import PureYAML
+import Testing
+
+@Suite("Directives after a document-end marker")
+struct DirectiveAfterDocumentEndTests {
+    @Test("A directive after `...` begins the next document")
+    func test_directiveAfterDocumentEndStartsNextDocument() throws {
+        let docs = try PureYAML.parseStream("a\n...\n%YAML 1.2\n---\nb\n")
+        #expect(docs.count == 2)
+        #expect(docs[0].value == .string("a"))
+        #expect(docs[1].value == .string("b"))
+    }
+
+    @Test("A %TAG directive may be repeated for each document after `...`")
+    func test_repeatedTagDirectivePerDocument() throws {
+        let docs = try PureYAML.parseStream(
+            "%TAG !m! !my-\n--- !m!light fluorescent\n...\n%TAG !m! !my-\n--- !m!light green\n",
+        )
+        #expect(docs.count == 2)
+    }
+
+    @Test("A directive after `...` still requires its own document start")
+    func test_directiveAfterDocumentEndStillRequiresDocument() throws {
+        #expect(throws: PureYAML.Parsing.ParseError.self) {
+            try PureYAML.parseStream("a\n...\n%YAML 1.2\n")
+        }
+    }
+}