Refactor validation error handling to use StringBuilder for prefix management

Author: RaniAgus

javalidation/src/main/java/io/github/raniagus/javalidation/IndexCollectorWrapper.java

@@ -29,7 +29,13 @@ public Supplier<C> supplier() {
 
     @Override
     public BiConsumer<C, Result<T>> accumulator() {
-        return (c, result) -> c.add(result.withPrefix(prefix, "[", index++, "]"));
+        return (c, result) -> c.add(
+                result,
+                new StringBuilder(prefix)
+                        .append('[')
+                        .append(index++)
+                        .append(']')
+        );
     }
 
     @Override

javalidation/src/main/java/io/github/raniagus/javalidation/ResultCollector.java

@@ -24,6 +24,14 @@ void add(Result<T> result) {
         }
     }
 
+    void add(Result<T> result, StringBuilder prefix) {
+        switch (result) {
+            case Result.Ok<T>(T value) -> values.add(value);
+            case Result.Err<T>(ValidationErrors validationErrors) ->
+                    validation.addAll(validationErrors, prefix);
+        }
+    }
+
     R finish() {
         return finish(values, validation);
     }

javalidation/src/main/java/io/github/raniagus/javalidation/Validation.java

@@ -187,24 +187,21 @@ public Validation addAll(ValidationErrors errors) {
      * //     }
      * }</pre>
      *
-     * @param prefix the prefix to add to all field paths (must not be null)
      * @param errors the validation errors to merge (must not be null)
+     * @param prefix the prefix to add to all field paths (must not be null)
      * @return this validation for method chaining
      * @throws NullPointerException if prefix or errors is null
      * @see ValidationErrors#withPrefix(String)
      */
-    public Validation addAll(String prefix, ValidationErrors errors) {
+    public Validation addAll(ValidationErrors errors, StringBuilder prefix) {
         Objects.requireNonNull(prefix);
         Objects.requireNonNull(errors);
         if (!errors.rootErrors().isEmpty()) {
-            addFieldErrors(prefix, errors.rootErrors());
+            addFieldErrors(prefix.toString(), errors.rootErrors());
         }
-        StringBuilder prefixBuilder = new StringBuilder(prefix).append(".");
-        int prefixLength = prefixBuilder.length();
+        StringBuilder prefixResult = prefix.append('.');
         for (Map.Entry<String, List<TemplateString>> entry : errors.fieldErrors().entrySet()) {
-            prefixBuilder.append(entry.getKey());
-            addFieldErrors(prefixBuilder.toString(), entry.getValue());
-            prefixBuilder.setLength(prefixLength);
+            addFieldErrors(prefixResult + entry.getKey(), entry.getValue());
         }
         return this;
     }

javalidation/src/main/java/io/github/raniagus/javalidation/ValidationErrors.java

@@ -178,7 +178,7 @@ public ValidationErrors withPrefix(String prefix) {
         if (!rootErrors.isEmpty()) {
             prefixedFieldErrors.put(prefix, rootErrors);
         }
-        String dotPrefix = prefix + ".";
+        String dotPrefix = prefix + '.';
         for (Map.Entry<String, List<TemplateString>> entry : fieldErrors.entrySet()) {
             prefixedFieldErrors.put(dotPrefix + entry.getKey(), entry.getValue());
         }

javalidation/src/test/java/io/github/raniagus/javalidation/ValidationTest.java

@@ -118,7 +118,7 @@ void givenNull_whenAddAll_thenThrowsNullPointerException() {
     void givenFieldErrors_whenAddAllWithPrefix_thenPrefixesFieldNames() {
         var validationErrors = ValidationErrors.ofField("field", "error");
         var validation = Validation.create()
-                .addAll("root", validationErrors);
+                .addAll(validationErrors, new StringBuilder("root"));
 
         var errors = validation.finish();
         assertThat(errors.fieldErrors()).containsKey("root.field");
@@ -128,29 +128,12 @@ void givenFieldErrors_whenAddAllWithPrefix_thenPrefixesFieldNames() {
     void givenRootErrors_whenAddAllWithPrefix_thenConvertsToFieldErrors() {
         var validationErrors = ValidationErrors.ofRoot("root error");
         var validation = Validation.create()
-                .addAll("prefix", validationErrors);
+                .addAll(validationErrors, new StringBuilder("prefix"));
 
         var errors = validation.finish();
         assertThat(errors.fieldErrors()).containsKey("prefix");
     }
 
-    @Test
-    void givenNullPrefix_whenAddAllWithPrefix_thenThrowsNullPointerException() {
-        var validation = Validation.create();
-        var validationErrors = ValidationErrors.ofRoot("error");
-
-        assertThatThrownBy(() -> validation.addAll(null, validationErrors))
-                .isInstanceOf(NullPointerException.class);
-    }
-
-    @Test
-    void givenNullValidationErrors_whenAddAllWithPrefix_thenThrowsNullPointerException() {
-        var validation = Validation.create();
-
-        assertThatThrownBy(() -> validation.addAll("prefix", null))
-                .isInstanceOf(NullPointerException.class);
-    }
-
     // -- finish --
 
     @Test