feat: Enhance message handling with HeapString for improved memory management

Author: gedaiu

operation-snapshots.md

@@ -168,7 +168,7 @@ struct Evaluation {
 
     printer.info("ASSERTION FAILED: ");
 
-    foreach(message; result.messages) {
+    foreach(ref message; result.messages) {
       printer.print(message);
     }
 

source/fluentasserts/core/evaluation.d

@@ -190,6 +190,22 @@ struct HeapData(T) {
         ptr[_length++] = item;
       }
     }
+
+    /// Appends contents from another HeapData.
+    void put(ref const HeapData other) @trusted @nogc nothrow {
+      if (other._length == 0) {
+        return;
+      }
+      put(other[]);
+    }
+
+    /// Appends contents from another HeapData (rvalue).
+    void put(const HeapData other) @trusted @nogc nothrow {
+      if (other._length == 0) {
+        return;
+      }
+      put(other[]);
+    }
   }
 
   /// Returns the contents as a slice.

source/fluentasserts/core/heapdata.d

@@ -7,6 +7,7 @@ import std.conv;
 import ddmp.diff;
 
 import fluentasserts.results.message : Message, ResultGlyphs;
+import fluentasserts.core.heapdata : HeapString;
 public import fluentasserts.core.array : FixedArray, FixedAppender, FixedStringArray;
 
 @safe:
@@ -94,18 +95,25 @@ struct AssertResult {
       .replace("\t", ResultGlyphs.tab);
   }
 
-  /// Returns the message as a plain string.
-  string messageString() nothrow @trusted inout {
-    string result;
-    foreach (m; messages) {
-      result ~= m.text;
+  /// Returns the message as a HeapString.
+  HeapString messageString() nothrow @trusted @nogc inout {
+    // Calculate total size needed
+    size_t totalSize = 0;
+    foreach (ref m; messages) {
+      totalSize += m.text.length;
+    }
+
+    // Preallocate and copy
+    HeapString result = HeapString.create(totalSize);
+    foreach (ref m; messages) {
+      result.put(m.text[]);
     }
     return result;
   }
 
   /// Converts the entire result to a displayable string.
   string toString() nothrow @trusted inout {
-    return messageString();
+    return messageString()[].idup;
   }
 
   /// Adds a message to the result.

source/fluentasserts/results/asserts.d

@@ -4,6 +4,8 @@ module fluentasserts.results.message;
 
 import std.string;
 
+import fluentasserts.core.heapdata : HeapString, toHeapString;
+
 @safe:
 
 /// Glyphs used to display special characters in the results.
@@ -119,23 +121,23 @@ struct Message {
   Type type;
 
   /// The text content of this message
-  string text;
+  HeapString text;
 
   /// Constructs a message with the given type and text.
-  this(Type type, string text) nothrow @nogc {
+  this(Type type, string text) nothrow @trusted @nogc {
     this.type = type;
-    this.text = text;
+    this.text = toHeapString(text);
   }
 
   /// Returns the raw text content. Use formattedText() for display with special formatting.
-  string toString() nothrow @nogc inout {
-    return text;
+  const(char)[] toString() nothrow @nogc inout {
+    return text[];
   }
 
   /// Returns the text with special character replacements and type-specific formatting.
   /// This allocates memory and should be used only for display purposes.
   string formattedText() nothrow inout {
-    string content = text;
+    string content = text[].idup;
 
     if (type == Type.value || type == Type.insert || type == Type.delete_) {
       content = content
@@ -147,13 +149,13 @@ struct Message {
 
     switch (type) {
       case Type.title:
-        return "\n\n" ~ text ~ "\n";
+        return "\n\n" ~ text[].idup ~ "\n";
       case Type.insert:
         return "[-" ~ content ~ "]";
       case Type.delete_:
         return "[+" ~ content ~ "]";
       case Type.category:
-        return "\n" ~ text ~ "";
+        return "\n" ~ text[].idup ~ "";
       default:
         return content;
     }

source/fluentasserts/results/message.d

@@ -50,7 +50,7 @@ version (unittest) {
       import std.conv : to;
 
       try {
-        buffer ~= "[" ~ message.type.to!string ~ ":" ~ message.text ~ "]";
+        buffer ~= "[" ~ message.type.to!string ~ ":" ~ message.text[].idup ~ "]";
       } catch (Exception) {
         buffer ~= "ERROR";
       }
@@ -164,7 +164,7 @@ class StringResultPrinter : ResultPrinter {
   nothrow:
 
     void print(Message message) {
-      buffer.put(message.text);
+      buffer.put(message.text[]);
     }
 
     void primary(string text) {