Fix text rendering regression for indented documents (#65)

Plot 0.9.0 introduced a minor regression for documents that are rendered with indentation,
in that plain text nodes would always be rendered on a new line. This patch fixes that by
differentiating between plain text output and element-based output, and only the latter
causes a new line to be inserted, preserving the previous rendering behavior.

Components that are made up of just plain text also get this behavior, and the unit test
that verifies indented documents has been expanded to also cover these cases.

Sources/Plot/Internal/ElementRenderingBuffer.swift

@@ -35,8 +35,8 @@ internal final class ElementRenderingBuffer {
         }
     }
 
-    func add(_ text: String) {
-        if indentation != nil {
+    func add(_ text: String, isPlainText: Bool) {
+        if !isPlainText, indentation != nil {
             body.append("\n")
         }
 

Sources/Plot/Internal/Renderer.swift

@@ -12,6 +12,7 @@ internal struct Renderer {
     private var environment: Environment
     private var elementWrapper: ElementWrapper?
     private var elementBuffer: ElementRenderingBuffer?
+    private var containsElement = false
 }
 
 extension Renderer {
@@ -30,7 +31,7 @@ extension Renderer {
     }
 
     mutating func renderRawText(_ text: String) {
-        renderRawText(text, wrapIfNeeded: true)
+        renderRawText(text, isPlainText: true, wrapIfNeeded: true)
     }
 
     mutating func renderText(_ text: String) {
@@ -72,8 +73,13 @@ extension Renderer {
         }
 
         deferredAttributes.forEach(buffer.add)
-        renderRawText(buffer.flush(), wrapIfNeeded: false)
         elementBuffer?.containsChildElements = true
+        containsElement = true
+
+        renderRawText(buffer.flush(),
+            isPlainText: false,
+            wrapIfNeeded: false
+        )
     }
 
     mutating func renderAttribute<T>(_ attribute: Attribute<T>) {
@@ -119,20 +125,29 @@ extension Renderer {
             )
         }
 
-        renderRawText(renderer.result, wrapIfNeeded: false)
+        renderRawText(renderer.result,
+            isPlainText: !renderer.containsElement,
+            wrapIfNeeded: false
+        )
+
+        containsElement = renderer.containsElement
     }
 }
 
 private extension Renderer {
-    mutating func renderRawText(_ text: String, wrapIfNeeded: Bool) {
+    mutating func renderRawText(
+        _ text: String,
+        isPlainText: Bool,
+        wrapIfNeeded: Bool
+    ) {
         if wrapIfNeeded {
             if let wrapper = elementWrapper {
                 return renderComponent(wrapper.body(Node<Any>.raw(text)))
             }
         }
 
         if let elementBuffer = elementBuffer {
-            elementBuffer.add(text)
+            elementBuffer.add(text, isPlainText: isPlainText)
         } else {
             if indentation != nil && !result.isEmpty {
                 result.append("\n")

Tests/PlotTests/DocumentTests.swift

@@ -26,9 +26,16 @@ final class DocumentTests: XCTestCase {
                     .element(named: "two", nodes: [
                         .selfClosedElement(named: "three")
                     ]),
-                    .element(named: "four")
+                    .text("four "),
+                    .component(Text("five")),
+                    .component(Element.named("six", nodes: [
+                        .text("seven")
+                    ])),
+                    .element(named: "eight", nodes: [
+                        .text("nine")
+                    ])
                 ]),
-                .selfClosed(named: "five", attributes: [
+                .selfClosed(named: "ten", attributes: [
                     Attribute(name: "key", value: "value")
                 ])
             ]
@@ -38,10 +45,11 @@ final class DocumentTests: XCTestCase {
         <one>
             <two>
                 <three/>
-            </two>
-            <four></four>
+            </two>four five
+            <six>seven</six>
+            <eight>nine</eight>
         </one>
-        <five key="value"/>
+        <ten key="value"/>
         """)
     }