feat: add minLength/maxLength validation for String inputs

comfy_api/latest/_io.py

@@ -326,11 +326,14 @@ class String(ComfyTypeIO):
         '''String input.'''
         def __init__(self, id: str, display_name: str=None, optional=False, tooltip: str=None, lazy: bool=None,
                     multiline=False, placeholder: str=None, default: str=None, dynamic_prompts: bool=None,
-                    socketless: bool=None, force_input: bool=None, extra_dict=None, raw_link: bool=None, advanced: bool=None):
+                    socketless: bool=None, force_input: bool=None, extra_dict=None, raw_link: bool=None, advanced: bool=None,
+                    min_length: int=None, max_length: int=None):
             super().__init__(id, display_name, optional, tooltip, lazy, default, socketless, None, force_input, extra_dict, raw_link, advanced)
             self.multiline = multiline
             self.placeholder = placeholder
             self.dynamic_prompts = dynamic_prompts
+            self.min_length = min_length
+            self.max_length = max_length
             self.default: str
 
         def as_dict(self):
@@ -338,6 +341,8 @@ class String(ComfyTypeIO):
                 "multiline": self.multiline,
                 "placeholder": self.placeholder,
                 "dynamicPrompts": self.dynamic_prompts,
+                "minLength": self.min_length,
+                "maxLength": self.max_length,
             })
 
 @comfytype(io_type="COMBO")

execution.py

@@ -81,7 +81,7 @@ class IsChangedCache:
             return self.is_changed[node_id]
 
         # Intentionally do not use cached outputs here. We only want constants in IS_CHANGED
-        input_data_all, _, v3_data = get_input_data(node["inputs"], class_def, node_id, None)
+        input_data_all, _, v3_data, _ = get_input_data(node["inputs"], class_def, node_id, None)
         try:
             is_changed = await _async_map_node_over_list(self.prompt_id, node_id, class_def, input_data_all, is_changed_name, v3_data=v3_data)
             is_changed = await resolve_map_node_over_list_results(is_changed)
@@ -213,7 +213,35 @@ def get_input_data(inputs, class_def, unique_id, execution_list=None, dynprompt=
                 if h[x] == "API_KEY_COMFY_ORG":
                     input_data_all[x] = [extra_data.get("api_key_comfy_org", None)]
     v3_data["hidden_inputs"] = hidden_inputs_v3
-    return input_data_all, missing_keys, v3_data
+    return input_data_all, missing_keys, v3_data, valid_inputs
+
+def validate_resolved_inputs(input_data_all, class_def, valid_inputs):
+    """Validate resolved input values against schema constraints.
+
+    This is needed because validate_inputs() only sees direct widget values.
+    Linked inputs aren't resolved during validate_inputs(), so this runs after resolution to catch any violations.
+    """
+    for x, values in input_data_all.items():
+        input_type, input_category, extra_info = get_input_info(class_def, x, valid_inputs)
+        if input_type != "STRING":
+            continue
+        min_length = extra_info.get("minLength")
+        max_length = extra_info.get("maxLength")
+        if min_length is None and max_length is None:
+            continue
+        for val in values:
+            if val is None or not isinstance(val, str):
+                continue
+            if min_length is not None and len(val) < min_length:
+                raise ValueError(
+                    f"Input '{x}': value length {len(val)} is shorter than "
+                    f"minimum length of {min_length}"
+                )
+            if max_length is not None and len(val) > max_length:
+                raise ValueError(
+                    f"Input '{x}': value length {len(val)} is longer than "
+                    f"maximum length of {max_length}"
+                )
 
 map_node_over_list = None #Don't hook this please
 
@@ -469,7 +497,7 @@ async def execute(server, dynprompt, caches, current_item, extra_data, executed,
             has_subgraph = False
         else:
             get_progress_state().start_progress(unique_id)
-            input_data_all, missing_keys, v3_data = get_input_data(inputs, class_def, unique_id, execution_list, dynprompt, extra_data)
+            input_data_all, missing_keys, v3_data, valid_inputs = get_input_data(inputs, class_def, unique_id, execution_list, dynprompt, extra_data)
             if server.client_id is not None:
                 server.last_node_id = display_node_id
                 server.send_sync("executing", { "node": unique_id, "display_node": display_node_id, "prompt_id": prompt_id }, server.client_id)
@@ -498,6 +526,8 @@ async def execute(server, dynprompt, caches, current_item, extra_data, executed,
                         execution_list.make_input_strong_link(unique_id, i)
                     return (ExecutionResult.PENDING, None, None)
 
+            validate_resolved_inputs(input_data_all, class_def, valid_inputs)
+
             def execution_block_cb(block):
                 if block.message is not None:
                     mes = {
@@ -940,6 +970,34 @@ async def validate_inputs(prompt_id, prompt, item, validated):
                     errors.append(error)
                     continue
 
+                if input_type == "STRING":
+                    if "minLength" in extra_info and len(val) < extra_info["minLength"]:
+                        error = {
+                            "type": "value_shorter_than_min_length",
+                            "message": "Value length {} shorter than min length of {}".format(len(val), extra_info["minLength"]),
+                            "details": f"{x}",
+                            "extra_info": {
+                                "input_name": x,
+                                "input_config": info,
+                                "received_value": val,
+                            }
+                        }
+                        errors.append(error)
+                        continue
+                    if "maxLength" in extra_info and len(val) > extra_info["maxLength"]:
+                        error = {
+                            "type": "value_longer_than_max_length",
+                            "message": "Value length {} longer than max length of {}".format(len(val), extra_info["maxLength"]),
+                            "details": f"{x}",
+                            "extra_info": {
+                                "input_name": x,
+                                "input_config": info,
+                                "received_value": val,
+                            }
+                        }
+                        errors.append(error)
+                        continue
+
                 if isinstance(input_type, list) or input_type == io.Combo.io_type:
                     if input_type == io.Combo.io_type:
                         combo_options = extra_info.get("options", [])
@@ -971,7 +1029,7 @@ async def validate_inputs(prompt_id, prompt, item, validated):
                         continue
 
     if len(validate_function_inputs) > 0 or validate_has_kwargs:
-        input_data_all, _, v3_data = get_input_data(inputs, obj_class, unique_id)
+        input_data_all, _, v3_data, _ = get_input_data(inputs, obj_class, unique_id)
         input_filtered = {}
         for x in input_data_all:
             if x in validate_function_inputs or validate_has_kwargs:

tests/execution/test_execution.py

@@ -1011,3 +1011,49 @@ class TestExecution:
         """Test getting a non-existent job returns 404"""
         job = client.get_job("nonexistent-job-id")
         assert job is None, "Non-existent job should return None"
+
+
+    @pytest.mark.parametrize("text, expect_error", [
+        ("hello", False),       # 5 chars, within [3, 10]
+        ("abc", False),         # 3 chars, exact min boundary
+        ("abcdefghij", False),  # 10 chars, exact max boundary
+        ("ab", True),           # 2 chars, below min
+        ("abcdefghijk", True),  # 11 chars, above max
+        ("", True),             # 0 chars, below min
+    ])
+    def test_string_length_widget_validation(self, text, expect_error, client: ComfyClient, builder: GraphBuilder):
+        """Test minLength/maxLength validation for direct widget values (validate_inputs path)."""
+        g = builder
+        node = g.node("StubStringWithLength", text=text)
+        g.node("SaveImage", images=node.out(0))
+        if expect_error:
+            with pytest.raises(urllib.error.HTTPError) as exc_info:
+                client.run(g)
+            assert exc_info.value.code == 400
+        else:
+            client.run(g)
+
+
+    @pytest.mark.parametrize("text, expect_error", [
+        ("hello", False),       # 5 chars, within [3, 10]
+        ("abc", False),         # 3 chars, exact min boundary
+        ("abcdefghij", False),  # 10 chars, exact max boundary
+        ("ab", True),           # 2 chars, below min
+        ("abcdefghijk", True),  # 11 chars, above max
+        ("", True),             # 0 chars, below min
+    ])
+    def test_string_length_linked_validation(self, text, expect_error, client: ComfyClient, builder: GraphBuilder):
+        """Test minLength/maxLength validation for linked inputs (validate_resolved_inputs path)."""
+        g = builder
+        str_node = g.node("StubStringOutput", value=text)
+        node = g.node("StubStringWithLength", text=str_node.out(0))
+        g.node("SaveImage", images=node.out(0))
+
+        if expect_error:
+            try:
+                client.run(g)
+                assert False, "Should have raised an error"
+            except Exception as e:
+                assert 'prompt_id' in e.args[0], f"Did not get proper error message: {e}"
+        else:
+            client.run(g)

tests/execution/testing_nodes/testing-pack/stubs.py

@@ -113,12 +113,48 @@ class StubFloat:
     def stub_float(self, value):
         return (value,)
 
+class StubStringOutput:
+    @classmethod
+    def INPUT_TYPES(cls):
+        return {
+            "required": {
+                "value": ("STRING", {"default": ""}),
+            },
+        }
+
+    RETURN_TYPES = ("STRING",)
+    FUNCTION = "stub_string"
+
+    CATEGORY = "Testing/Stub Nodes"
+
+    def stub_string(self, value):
+        return (value,)
+
+class StubStringWithLength:
+    @classmethod
+    def INPUT_TYPES(cls):
+        return {
+            "required": {
+                "text": ("STRING", {"default": "hello", "minLength": 3, "maxLength": 10}),
+            },
+        }
+
+    RETURN_TYPES = ("IMAGE",)
+    FUNCTION = "stub_string_with_length"
+
+    CATEGORY = "Testing/Stub Nodes"
+
+    def stub_string_with_length(self, text):
+        return (torch.zeros(1, 64, 64, 3),)
+
 TEST_STUB_NODE_CLASS_MAPPINGS = {
     "StubImage": StubImage,
     "StubConstantImage": StubConstantImage,
     "StubMask": StubMask,
     "StubInt": StubInt,
     "StubFloat": StubFloat,
+    "StubStringOutput": StubStringOutput,
+    "StubStringWithLength": StubStringWithLength,
 }
 TEST_STUB_NODE_DISPLAY_NAME_MAPPINGS = {
     "StubImage": "Stub Image",
@@ -126,4 +162,6 @@ TEST_STUB_NODE_DISPLAY_NAME_MAPPINGS = {
     "StubMask": "Stub Mask",
     "StubInt": "Stub Int",
     "StubFloat": "Stub Float",
+    "StubStringOutput": "Stub String Output",
+    "StubStringWithLength": "Stub String With Length",
 }