don't try to add a line to a closed block directive (#113)

rdar://105221177

Author: QuietMisdreavus

Sources/Markdown/Parser/BlockDirectiveParser.swift

@@ -1009,7 +1009,10 @@ struct ParseContainerStack {
                 // A pending block directive can accept this line if it is in the middle of
                 // parsing arguments text (to allow indentation to align arguments) or
                 // if the line isn't taking part in a code block.
-                let canAcceptLine = pendingBlockDirective.parseState == .argumentsText || !isCodeFenceOrIndentedCodeBlock(on: line)
+                let canAcceptLine =
+                    pendingBlockDirective.parseState != .done &&
+                    (pendingBlockDirective.parseState == .argumentsText ||
+                     !isCodeFenceOrIndentedCodeBlock(on: line))
                 if canAcceptLine && pendingBlockDirective.accept(line) {
                     pop()
                     push(.blockDirective(pendingBlockDirective, children))

Tests/MarkdownTests/Parsing/BlockDirectiveParserTests.swift

@@ -991,7 +991,7 @@ class BlockDirectiveArgumentParserTests: XCTestCase {
         }
         """
         let document = Document(parsing: source, options: [.parseBlockDirectives])
-
+        
         let expectedDump = #"""
         Document @1:1-4:2
         ├─ BlockDirective @1:1-1:19 name: "blah"
@@ -1003,4 +1003,21 @@ class BlockDirectiveArgumentParserTests: XCTestCase {
         """#
         XCTAssertEqual(document.debugDescription(options: .printSourceLocations), expectedDump)
     }
+
+    func testSingleLineDirectiveWithTrailingContent() {
+        let source = """
+        @blah { content }
+        content
+        """
+        let document = Document(parsing: source, options: [.parseBlockDirectives])
+        let expectedDump = #"""
+        Document @1:1-2:8
+        ├─ BlockDirective @1:1-1:18 name: "blah"
+        │  └─ Paragraph @1:9-1:16
+        │     └─ Text @1:9-1:16 "content"
+        └─ Paragraph @2:1-2:8
+           └─ Text @2:1-2:8 "content"
+        """#
+        XCTAssertEqual(document.debugDescription(options: .printSourceLocations), expectedDump)
+    }
 }