track inner indentation for doxygen commands

Sources/Markdown/Markdown.docc/Markdown/DoxygenCommands.md

@@ -29,9 +29,16 @@ This is the thing that is modified.
 }
 ```
 
-Doxygen commands are not parsed within code blocks or block directive content. No indentation
-adjustment is performed on paragraph arguments that span multiple lines, unlike with block directive
-content.
+Trailing lines in a command's description are allowed to be indented relative to the command. For
+example, the description below is parsed as a paragraph, not a code block:
+
+```markdown
+\param thing
+    The thing.
+    This is the thing that is modified.
+```
+
+Doxygen commands are not parsed within code blocks or block directive content.
 
 ## Topics
 

Sources/Markdown/Parser/BlockDirectiveParser.swift

@@ -241,14 +241,26 @@ struct PendingDoxygenCommand {
 
     var atLocation: SourceLocation
 
+    var atSignIndentation: Int
+
     var nameLocation: SourceLocation
 
+    var innerIndentation: Int? = nil
+
     var kind: CommandKind
 
     var endLocation: SourceLocation
 
+    var indentationAdjustment: Int {
+        innerIndentation ?? atSignIndentation
+    }
+
     mutating func addLine(_ line: TrimmedLine) {
         endLocation = SourceLocation(line: line.lineNumber ?? 0, column: line.untrimmedText.count + 1, source: line.source)
+
+        if innerIndentation == nil, line.location?.line != atLocation.line, !line.isEmptyOrAllWhitespace {
+            innerIndentation = line.indentationColumnCount
+        }
     }
 }
 
@@ -655,8 +667,8 @@ private enum ParseContainer: CustomStringConvertible {
             return parent?.indentationAdjustment(under: nil) ?? 0
         case .blockDirective(let pendingBlockDirective, _):
             return pendingBlockDirective.indentationColumnCount
-        case .doxygenCommand:
-            return parent?.indentationAdjustment(under: nil) ?? 0
+        case .doxygenCommand(let pendingCommand, _):
+            return pendingCommand.indentationAdjustment
         }
     }
 
@@ -842,6 +854,7 @@ struct ParseContainerStack {
         guard !isCodeFenceOrIndentedCodeBlock(on: line) else { return nil }
 
         var remainder = line
+        let indent = remainder.lexWhitespace()
         guard let at = remainder.lex(until: { ch in
             switch ch {
             case "@", "\\":
@@ -871,6 +884,7 @@ struct ParseContainerStack {
             remainder.lexWhitespace()
             var pendingCommand = PendingDoxygenCommand(
                 atLocation: at.range!.lowerBound,
+                atSignIndentation: indent?.text.count ?? 0,
                 nameLocation: name.range!.lowerBound,
                 kind: .param(name: paramName.text),
                 endLocation: name.range!.upperBound)
@@ -879,6 +893,7 @@ struct ParseContainerStack {
         case "return", "returns", "result":
             var pendingCommand = PendingDoxygenCommand(
                 atLocation: at.range!.lowerBound,
+                atSignIndentation: indent?.text.count ?? 0,
                 nameLocation: name.range!.lowerBound,
                 kind: .returns,
                 endLocation: name.range!.upperBound)

Tests/MarkdownTests/Parsing/DoxygenCommandParserTests.swift

@@ -91,6 +91,65 @@ class DoxygenCommandParserTests: XCTestCase {
         XCTAssertEqual(document.debugDescription(), expectedDump)
     }
 
+    func testParseIndentedDescription() {
+        let source = """
+        @param thing
+            The thing.
+        """
+
+        let document = Document(parsing: source, options: parseOptions)
+
+        let expectedDump = """
+        Document
+        └─ DoxygenParameter parameter: thing
+           └─ Paragraph
+              └─ Text "The thing."
+        """
+        XCTAssertEqual(document.debugDescription(), expectedDump)
+    }
+
+    func testParseMultilineIndentedDescription() {
+        let source = """
+        @param thing The thing.
+            This is the thing that is messed with.
+        """
+
+        let document = Document(parsing: source, options: parseOptions)
+
+        let expectedDump = """
+        Document
+        └─ DoxygenParameter parameter: thing
+           └─ Paragraph
+              ├─ Text "The thing."
+              ├─ SoftBreak
+              └─ Text "This is the thing that is messed with."
+        """
+        XCTAssertEqual(document.debugDescription(), expectedDump)
+    }
+
+    func testParseWithIndentedAtSign() {
+        let source = """
+        Method description.
+
+         @param thing The thing.
+            This is the thing that is messed with.
+        """
+
+        let document = Document(parsing: source, options: parseOptions)
+
+        let expectedDump = """
+        Document
+        ├─ Paragraph
+        │  └─ Text "Method description."
+        └─ DoxygenParameter parameter: thing
+           └─ Paragraph
+              ├─ Text "The thing."
+              ├─ SoftBreak
+              └─ Text "This is the thing that is messed with."
+        """
+        XCTAssertEqual(document.debugDescription(), expectedDump)
+    }
+
     func testBreakDescriptionWithBlankLine() {
         let source = """
         @param thing The thing.
@@ -188,7 +247,6 @@ class DoxygenCommandParserTests: XCTestCase {
 
         let document = Document(parsing: source, options: parseOptions)
 
-        // FIXME: The source location for the first description line is wrong
         let expectedDump = """
         Document @1:1-2:39
         └─ DoxygenParameter @1:1-2:39 parameter: thing
@@ -200,6 +258,48 @@ class DoxygenCommandParserTests: XCTestCase {
         XCTAssertEqual(document.debugDescription(options: .printSourceLocations), expectedDump)
     }
 
+    func testSourceLocationsWithIndentation() {
+        let source = """
+        @param thing The thing.
+            This is the thing that is messed with.
+        """
+
+        let document = Document(parsing: source, options: parseOptions)
+
+        let expectedDump = """
+        Document @1:1-2:43
+        └─ DoxygenParameter @1:1-2:43 parameter: thing
+           └─ Paragraph @1:14-2:43
+              ├─ Text @1:14-1:24 "The thing."
+              ├─ SoftBreak
+              └─ Text @2:5-2:43 "This is the thing that is messed with."
+        """
+        XCTAssertEqual(document.debugDescription(options: .printSourceLocations), expectedDump)
+    }
+
+    func testSourceLocationsWithIndentedAtSign() {
+        let source = """
+        Method description.
+
+         @param thing The thing.
+            This is the thing that is messed with.
+        """
+
+        let document = Document(parsing: source, options: parseOptions)
+
+        let expectedDump = """
+        Document @1:1-4:43
+        ├─ Paragraph @1:1-1:20
+        │  └─ Text @1:1-1:20 "Method description."
+        └─ DoxygenParameter @3:2-4:43 parameter: thing
+           └─ Paragraph @3:15-4:43
+              ├─ Text @3:15-3:25 "The thing."
+              ├─ SoftBreak
+              └─ Text @4:5-4:43 "This is the thing that is messed with."
+        """
+        XCTAssertEqual(document.debugDescription(options: .printSourceLocations), expectedDump)
+    }
+
     func testDoesNotParseWithoutOption() {
         do {
             let source = """