Render error caret for the last character of the parsing context

core/src/main/java/org/spongepowered/configurate/loader/ParsingException.java

@@ -175,7 +175,9 @@ public int column() {
 
         if (this.context != null) {
             message.append(System.lineSeparator()).append(this.context);
-            if (this.column >= 0 && this.column < this.context.length()) {
+            // column is 1-indexed: column == context.length() points at the last character,
+            // so the caret drawn at position (column - 1) stays within the context bounds.
+            if (this.column >= 0 && this.column <= this.context.length()) {
                 message.append(System.lineSeparator());
                 if (this.column > 0) {
                     final char[] spaces = new char[this.column - 1];

core/src/test/java/org/spongepowered/configurate/loader/ParsingExceptionTest.java

@@ -0,0 +1,36 @@
+package org.spongepowered.configurate.loader;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import org.junit.jupiter.api.Test;
+
+class ParsingExceptionTest {
+
+    // column is 1-indexed, so column == context.length() points at the last char.
+    // The caret must be rendered there too. Previously the guard was
+    // `column < context.length()`, which dropped the caret for the last char (#625).
+    @Test
+    void caretRenderedForLastColumn() {
+        final String context = "hello"; // length 5
+        final String message = new ParsingException(1, context.length(), context, "err", null).getMessage();
+
+        // The caret sits under the last character: (length - 1) leading spaces, then '^'.
+        final int caretIndex = message.indexOf('^');
+        assertTrue(caretIndex >= 0, "a caret should be rendered for the last column");
+        int leadingSpaces = 0;
+        for (int i = caretIndex - 1; i >= 0 && message.charAt(i) == ' '; i--) {
+            leadingSpaces++;
+        }
+        assertEquals(context.length() - 1, leadingSpaces, "caret should be aligned under the last character");
+    }
+
+    @Test
+    void caretNotRenderedBeyondContext() {
+        final String context = "hello";
+        final String message = new ParsingException(1, context.length() + 1, context, "err", null).getMessage();
+        assertFalse(message.contains("^"), "caret should not be rendered past the context");
+    }
+
+}