[modbus_client] Add continuous option to the read and send actions (#18542)

Co-authored-by: Claude <noreply@anthropic.com>

esphome/components/modbus/__init__.py

@@ -1,17 +1,23 @@
 from __future__ import annotations
 
 import logging
-from typing import Any, Literal
+from typing import Any, Literal, NamedTuple
 
 from esphome import pins
 import esphome.codegen as cg
 from esphome.components import uart
 import esphome.config_validation as cv
-from esphome.const import CONF_ADDRESS, CONF_DISABLE_CRC, CONF_FLOW_CONTROL_PIN, CONF_ID
+from esphome.const import (
+    CONF_ADDRESS,
+    CONF_CONTINUOUS,
+    CONF_DISABLE_CRC,
+    CONF_FLOW_CONTROL_PIN,
+    CONF_ID,
+)
 from esphome.cpp_generator import MockObj
 from esphome.cpp_helpers import gpio_pin_expression
 import esphome.final_validate as fv
-from esphome.types import ConfigType
+from esphome.types import ConfigType, TemplateArgsType
 
 _LOGGER = logging.getLogger(__name__)
 
@@ -48,6 +54,73 @@ CONF_TURNAROUND_TIME = "turnaround_time"
 
 MODBUS_ROLES = ["client", "server"]
 
+
+class _CommandOption(NamedTuple):
+    """One per-command option forwarded to the hub (modbus::CommandOptions)."""
+
+    conf_key: str
+    field: str  # the C++ field, and so the set_<field>() setter name
+    validator: Any  # the static (non-templatable) validator for the key
+    cpp_type: Any  # the C++ type the value is generated as
+    default: Any
+
+
+# Per-direction command options. Single-sourcing the schema and the setter generation here keeps
+# them from drifting; the C++ side must add the matching field per the rules documented on
+# CommandOptions (modbus.h).
+_COMMAND_OPTIONS: dict[str, list[_CommandOption]] = {
+    "read": [_CommandOption(CONF_CONTINUOUS, "continuous", cv.boolean, bool, False)],
+    "write": [],
+}
+
+
+def _command_options(direction: str) -> list[_CommandOption]:
+    try:
+        return _COMMAND_OPTIONS[direction]
+    except KeyError:
+        raise ValueError(f"unknown command-options direction {direction!r}") from None
+
+
+def command_options_schema(
+    *, direction: Literal["read", "write"], templatable: bool = False
+) -> dict[cv.Optional, Any]:
+    """Schema fragment for the per-command options a component forwards to the hub
+    (modbus::CommandOptions). Extend this into any schema that queues commands. Keys are
+    direction-specific so a schema never offers an option the hub would strip (e.g.
+    continuous on a write); the write side has no options yet. For actions (templatable=True the
+    keys also accept lambdas), register the values with register_templatable_command_options().
+    """
+    return {
+        cv.Optional(option.conf_key, default=option.default): (
+            cv.templatable(option.validator) if templatable else option.validator
+        )
+        for option in _command_options(direction)
+    }
+
+
+async def register_templatable_command_options(
+    var: MockObj, config: ConfigType, args: TemplateArgsType, direction: str
+) -> None:
+    """Generate the set_<option>() calls for the given direction's command options present in config.
+    Pass the same direction the action's command_options_schema() used, so the keys generated match
+    the ones the schema offered - a write action never emits a read option's setter. Options the
+    schema did not add are simply absent. The consumer's C++ class declares a matching
+    TEMPLATABLE_VALUE per option (e.g. TEMPLATABLE_VALUE(bool, continuous)).
+    """
+    for option in _command_options(direction):
+        if option.conf_key not in config:
+            continue
+        value = config[option.conf_key]
+        # Skip codegen when the value is its C++ zero (TemplatableFn::value() returns T{} when
+        # unset): behaviourally identical, and saves a thunk plus a setup() call per action.
+        if cg.is_template(value) or value != type(value)():
+            cg.add(
+                getattr(var, f"set_{option.field}")(
+                    await cg.templatable(value, args, option.cpp_type)
+                )
+            )
+
+
 CONFIG_SCHEMA = cv.typed_schema(
     {
         "client": cv.Schema(

esphome/components/modbus/modbus.cpp

@@ -146,7 +146,7 @@ bool ModbusClientHub::tx_buffer_empty() {
   // other states are mid-transaction or owed bookkeeping, not queued sends - and a READY continuous
   // poll does not count either, since it ranks below every one-shot, so a new send goes out first.
   for (const auto &cmd : this->tx_buffer_) {
-    if (cmd.state == FrameState::READY && !cmd.continuous)
+    if (cmd.state == FrameState::READY && !cmd.options.continuous)
       return false;
   }
   return true;
@@ -946,7 +946,7 @@ bool ModbusDeviceCommand::notify_retired() {
 bool ModbusDeviceCommand::response(std::span<const uint8_t> response_pdu) {
   this->state = this->state == FrameState::WAITING_RETIRED ? FrameState::RETIRED : FrameState::RECEIVED_RESPONSE;
   // A continuous poll is never consumed by its own response; a one-shot consumes one request here.
-  if (!this->continuous)
+  if (!this->options.continuous)
     this->decrement_pending();
   if (this->device == nullptr)
     return false;
@@ -1070,15 +1070,12 @@ bool ModbusClientHub::queue_pdu(uint8_t address, std::span<const uint8_t> pdu, M
     return false;
   }
 
+  // Normalize the caller's options in place (the param is a by-value copy) so everything stored or
+  // merged below carries effective options, never the raw request.
   // continuous is ignored for every mutating code (re-writing a value forever is never intended).
-  const bool mutates = priority == CommandPriority::WRITE;
-  bool continuous = false;
-  if (options.continuous) {
-    if (mutates) {
-      ESP_LOGV(TAG, "continuous is ignored for a mutating function (0x%X, address %" PRIu8 ")", pdu[0], address);
-    } else {
-      continuous = true;
-    }
+  if (options.continuous && priority == CommandPriority::WRITE) {
+    ESP_LOGW(TAG, "continuous is ignored for a mutating function (0x%X, address %" PRIu8 ")", pdu[0], address);
+    options.continuous = false;
   }
 
   // A duplicate of a live entry with the same owner is not queued twice; it resolves against that
@@ -1104,10 +1101,10 @@ bool ModbusClientHub::queue_pdu(uint8_t address, std::span<const uint8_t> pdu, M
       }
       return false;  // dropped: no entry, no callbacks - the refusal is the return value
     }
-    if (continuous) {
+    if (options.continuous) {
       item.make_continuous(true);
       ESP_LOGV(TAG, "Frame already active for %" PRIu8 ", now polled continuously", address);
-    } else if (item.continuous) {
+    } else if (item.options.continuous) {
       // A one-shot duplicate downgrades the poll to a one-shot: it runs one more cycle to serve this
       // request, then stops (mirrors continuous incoming converting a one-shot the other way).
       item.make_continuous(false);
@@ -1140,7 +1137,7 @@ bool ModbusClientHub::queue_pdu(uint8_t address, std::span<const uint8_t> pdu, M
 #endif
   ESP_LOGV(TAG, "Adding frame to tx queue: %" PRIu8 ":%s", address,
            format_hex_pretty_to(hex_buf, pdu.data(), pdu.size()));
-  this->tx_buffer_.emplace_back(device, address, pdu, continuous, this->next_seq_++);
+  this->tx_buffer_.emplace_back(device, address, pdu, options, this->next_seq_++);
   return true;
 }
 

esphome/components/modbus/modbus.h

@@ -118,6 +118,14 @@ enum class FrameState : uint8_t {
 };
 
 // Per-command send options. Append-only; pass via designated initializers ({.continuous = true}).
+// The queue entry stores this struct whole, so a new field arrives at the queue with no plumbing -
+// but it arrives inert. Every new field must define three rules before it does anything:
+//   1. normalization in queue_pdu() (is it valid for this function code? e.g. continuous is
+//      stripped for mutating codes),
+//   2. a merge rule for when a duplicate send absorbs into a live entry (continuous
+//      upgrades/downgrades via make_continuous(); a new field needs its own answer),
+//   3. teardown: retire() resets the whole struct; silent_retire() leaves it, relying on the sweep
+//      to erase the entry.
 struct CommandOptions {
   // A continuous poll lives in the queue until cancelled or failed; ignored for mutating codes.
   bool continuous{false};
@@ -126,26 +134,29 @@ struct CommandOptions {
 struct ModbusDeviceCommand {
   ModbusClientDevice *device;
   ModbusFrame frame;
-  FrameState state{FrameState::READY};
-  // A continuous poll is a subscription: pending fixed at 1, removed only by cancellation or failure.
-  bool continuous{false};
-  // Accepted requests this entry stands for, capped at max_pending(); drains one terminal each.
-  uint8_t pending{1};
   // Place-in-line stamp (hub's free-running counter); selection takes the oldest for round-robin
-  // fairness within a class. Meant to wrap.
+  // fairness within a class. Meant to wrap. Declared ahead of the byte fields so the tail packs
+  // densely and a growing CommandOptions eats trailing padding before enlarging the struct.
   uint16_t seq{0};
+  FrameState state{FrameState::READY};
+  // Accepted requests this entry stands for, capped at max_pending(); drains one terminal each.
+  // A continuous poll is a subscription: pending fixed at 1, removed only by cancellation or failure.
+  uint8_t pending{1};
+  // The entry's LIVE effective options, not a record of the caller's request: queue_pdu() normalizes
+  // before storing, duplicate absorption mutates continuous via make_continuous(), and retire() resets
+  // the struct (silent_retire() leaves it, relying on the sweep to erase the entry). See the
+  // CommandOptions comment for the rules a new field must define.
+  CommandOptions options;
 
-  // Build a command from a PDU span (caller bounds it to MAX_PDU_SIZE); fully initialized here.
+  // Build a command from a PDU span (caller bounds it to MAX_PDU_SIZE) and pre-normalized options;
+  // fully initialized here.
   ModbusDeviceCommand(ModbusClientDevice *device, uint8_t address, std::span<const uint8_t> pdu,
-                      bool continuous = false, uint16_t seq = 0)
-      : device(device),
-        frame(address, pdu.data(), static_cast<uint16_t>(pdu.size())),
-        continuous(continuous),
-        seq(seq) {}
+                      CommandOptions options = {}, uint16_t seq = 0)
+      : device(device), frame(address, pdu.data(), static_cast<uint16_t>(pdu.size())), seq(seq), options(options) {}
 
   // Transmit ordering class, derived (never stored): a continuous poll ranks below every one-shot.
   CommandPriority priority() const {
-    return this->continuous ? CommandPriority::CONTINUOUS : classify(this->frame.pdu()[0]);
+    return this->options.continuous ? CommandPriority::CONTINUOUS : classify(this->frame.pdu()[0]);
   }
   // Wire-derived class: mutating codes rank WRITE; exception-flagged codes are excluded.
   static CommandPriority classify(uint8_t function_code) {
@@ -161,7 +172,7 @@ struct ModbusDeviceCommand {
   uint8_t max_pending() const {
     const uint8_t fc = this->frame.pdu()[0];
     const bool requeueable = !helpers::is_function_code_exception(fc) && helpers::is_function_code_read_only(fc);
-    return (requeueable && !this->continuous) ? 2 : 1;
+    return (requeueable && !this->options.continuous) ? 2 : 1;
   }
   // Device-scoped clear: detach with no callback (device-less, pending 0). An entry still waiting for
   // a response keeps its state as a reply-ignoring shell that resolves silently; any other goes RETIRED.
@@ -196,11 +207,11 @@ struct ModbusDeviceCommand {
   // retroactively inflating that no-op.
   void make_continuous(bool continuous) {
     if (continuous) {
-      this->continuous = true;
+      this->options.continuous = true;
       this->pending = 1;
     } else {
       this->increment_pending();
-      this->continuous = false;
+      this->options.continuous = false;
     }
   }
   // Address-scoped clear: keep pending and device so the sweep delivers one on_not_sent() per un-run
@@ -218,7 +229,7 @@ struct ModbusDeviceCommand {
     } else if (!this->waiting_state()) {  // an already-retired shell stays put; off the wire -> RETIRED
       this->state = FrameState::RETIRED;
     }
-    this->continuous = false;
+    this->options = {};  // reset every option so a future field is torn down without editing here
   }
 
   // True while the entry is still waiting for a response; the erase pass exempts these even at pending 0.
@@ -253,6 +264,9 @@ struct ModbusDeviceCommand {
   bool notify_retired();
 
   /// True if this command carries the same wire frame (address + PDU) as the given one.
+  /// Cancellation matches the exact frame, not the action instance: a continuous poll whose
+  /// start_address (or other field) is templated produces one poll per distinct frame, and a later
+  /// cancel built from different argument values will not reach the polls it does not byte-match.
   bool same_frame(uint8_t address, std::span<const uint8_t> pdu) const {
     const auto own_pdu = this->frame.pdu();
     return own_pdu.size() == pdu.size() && this->frame.address() == address &&

esphome/components/modbus_client/__init__.py

@@ -7,6 +7,7 @@ from esphome.components import modbus
 import esphome.config_validation as cv
 from esphome.const import (
     CONF_ADDRESS,
+    CONF_CONTINUOUS,
     CONF_COUNT,
     CONF_ID,
     CONF_ON_ERROR,
@@ -156,16 +157,45 @@ _ACTION_BASE_SCHEMA = cv.Schema(
     }
 )
 
-MODBUS_CLIENT_SEND_SCHEMA = _ACTION_BASE_SCHEMA.extend(
-    {
-        cv.Required(CONF_PDU): cv.templatable(
-            cv.All(
-                cv.ensure_list(cv.hex_uint8_t),
-                cv.Length(min=1, max=modbus.MAX_PDU_SIZE),
-            )
-        ),
-        cv.Optional(CONF_ON_RESPONSE): _handler_schema(),
-    }
+# The write codes recognised by modbus::helpers::is_function_code_write() - keep in sync. 0x17
+# (read/write multiple) is included: it mutates, so the hub treats it as a write despite its read half.
+_WRITE_FUNCTION_CODES = frozenset({0x05, 0x06, 0x0F, 0x10, 0x16, 0x17})
+
+
+def _no_continuous_on_write(config: ConfigType) -> ConfigType:
+    """Reject `continuous: true` on a static write PDU: continuous polling only applies to reads.
+    Only the fully-static case is decidable here; the hub strips the flag from mutating PDUs at
+    runtime, so a templated pdu or continuous falls through to that backstop."""
+    pdu = config[CONF_PDU]
+    if (
+        isinstance(pdu, list)
+        and config.get(CONF_CONTINUOUS) is True
+        # Masking the exception bit (0x90 -> 0x10) makes this check stricter than the runtime hub,
+        # whose classify() treats an exception-flagged code as a read and leaves continuous in place.
+        and pdu[0] & 0x7F in _WRITE_FUNCTION_CODES
+    ):
+        raise cv.Invalid(
+            f"'{CONF_CONTINUOUS}: true' does not apply to a write PDU (function code "
+            f"0x{pdu[0]:02X}); continuous polling only applies to reads",
+            path=[CONF_CONTINUOUS],
+        )
+    return config
+
+
+MODBUS_CLIENT_SEND_SCHEMA = cv.All(
+    _ACTION_BASE_SCHEMA.extend(
+        {
+            cv.Required(CONF_PDU): cv.templatable(
+                cv.All(
+                    cv.ensure_list(cv.hex_uint8_t),
+                    cv.Length(min=1, max=modbus.MAX_PDU_SIZE),
+                )
+            ),
+            **modbus.command_options_schema(direction="read", templatable=True),
+            cv.Optional(CONF_ON_RESPONSE): _handler_schema(),
+        }
+    ),
+    _no_continuous_on_write,
 )
 
 
@@ -174,6 +204,7 @@ async def register_client_action(
     config: ConfigType,
     args: TemplateArgsType,
     response_args: TemplateArgsType,
+    command_direction: str = "read",
 ) -> cg.MockObj:
     """Wire the shared action plumbing: hub parent, templated device address, outcome triggers.
 
@@ -235,6 +266,12 @@ async def register_client_action(
         await automation.build_automation(
             var.get_not_sent_trigger(), [(_PDU_SPAN, "request")], not_sent_conf
         )
+    # Wire any command options the action's schema opted into (e.g. continuous on reads). Pass the
+    # matching direction so a write action never generates a read option's setter; the write side
+    # has no options yet, so this is a no-op there.
+    await modbus.register_templatable_command_options(
+        var, config, args, command_direction
+    )
     return var
 
 
@@ -318,6 +355,7 @@ def _read_schema(max_count: int) -> cv.All:
                 cv.Optional(CONF_COUNT, default=1): cv.templatable(
                     cv.int_range(min=1, max=max_count)
                 ),
+                **modbus.command_options_schema(direction="read", templatable=True),
             }
         ),
         _no_address_overflow(CONF_COUNT),
@@ -379,7 +417,9 @@ async def read_input_registers_to_code(config, action_id, template_arg, args):
 async def _write_single_to_code(config, action_id, template_arg, args, value_type):
     var = cg.new_Pvariable(action_id, template_arg)
     cg.add(var.set_value(await cg.templatable(config[CONF_VALUE], args, value_type)))
-    return await register_client_action(var, config, args, [])
+    return await register_client_action(
+        var, config, args, [], command_direction="write"
+    )
 
 
 @automation.register_action(
@@ -458,7 +498,9 @@ async def write_multiple_registers_to_code(config, action_id, template_arg, args
         arr_id = ID(f"{action_id}_values", is_declaration=True, type=cg.uint16)
         arr = cg.static_const_array(arr_id, cg.ArrayInitializer(*values))
         cg.add(var.set_values_static(arr, len(values)))
-    return await register_client_action(var, config, args, [])
+    return await register_client_action(
+        var, config, args, [], command_direction="write"
+    )
 
 
 @automation.register_action(
@@ -482,7 +524,9 @@ async def write_multiple_coils_to_code(config, action_id, template_arg, args):
         arr_id = ID(f"{action_id}_values", is_declaration=True, type=cg.uint8)
         arr = cg.static_const_array(arr_id, cg.ArrayInitializer(*packed))
         cg.add(var.set_values_static(arr, len(values)))
-    return await register_client_action(var, config, args, [])
+    return await register_client_action(
+        var, config, args, [], command_direction="write"
+    )
 
 
 # Read/write multiple registers (FC 0x17) writes one register block and reads another in a single

esphome/components/modbus_client/modbus_client.h

@@ -68,8 +68,8 @@ template<typename... Ts> class ClientActionBase : public Action<Ts...>, public m
   /// resolves through on_sent() alone), so resolve refusals here via on_not_sent.
   /// Takes a span, not a PduBuffer: the builders return right-sized buffers (a read PDU is 5 bytes), and
   /// a PduBuffer parameter would widen each one to the 253-byte maximum just to cross the call.
-  void send_or_resolve_(std::span<const uint8_t> pdu) {
-    if (!this->queue_pdu(pdu))
+  void send_or_resolve_(std::span<const uint8_t> pdu, modbus::CommandOptions options = {}) {
+    if (!this->queue_pdu(pdu, options))
       this->on_not_sent(pdu);
   }
 
@@ -80,6 +80,26 @@ template<typename... Ts> class ClientActionBase : public Action<Ts...>, public m
   retry_func_t retry_func_{nullptr};
 };
 
+/// The read-side per-command options (modbus::CommandOptions), declared once for every action that
+/// sends a read. Each option is templatable, so it cannot be built in Python the way modbus_controller
+/// builds its static struct; declaring the values here instead of per action means a new read option
+/// costs one TEMPLATABLE_VALUE plus one field below, and every read action picks it up.
+/// The read/write split mirrors _COMMAND_OPTIONS in the modbus component's Python
+/// (command_options_schema(direction="read") adds exactly these keys). When a write-side option
+/// arrives it gets a WriteCommandOptions twin, so write actions never carry read-only members.
+template<typename... Ts> class ReadCommandOptions {
+ public:
+  // Poll: re-queue after each success until downgraded (replay with false) or failed. The hub strips
+  // it for mutating function codes at the door (see modbus::CommandOptions).
+  TEMPLATABLE_VALUE(bool, continuous)
+
+ protected:
+  /// The options for this send, with every templatable value resolved against the action's arguments.
+  modbus::CommandOptions command_options_(const Ts &...x) const {
+    return {.continuous = this->continuous_.value(x...)};
+  }
+};
+
 /// modbus_client.send: fire a raw PDU (function code + data; the hub adds address and CRC). The reply is
 /// delivered raw - on_response(request, response) - deliberately bypassing the typed dispatch, so
 /// non-standard/custom transactions pass through untouched.
@@ -87,7 +107,8 @@ template<typename... Ts> class ClientActionBase : public Action<Ts...>, public m
 /// modbus::helpers::create_*_pdu() builders and return it directly (smaller builder results convert).
 /// A PduBuffer drops bytes past modbus::MAX_PDU_SIZE without reporting it (the hub's oversize check
 /// cannot fire - that limit is the capacity), so an over-long lambda-built PDU is silently truncated.
-template<typename... Ts> class ModbusClientSendAction : public ClientActionBase<Ts...> {
+template<typename... Ts>
+class ModbusClientSendAction : public ClientActionBase<Ts...>, public ReadCommandOptions<Ts...> {
  public:
   TEMPLATABLE_VALUE(modbus::helpers::PduBuffer, pdu)
 
@@ -95,7 +116,7 @@ template<typename... Ts> class ModbusClientSendAction : public ClientActionBase<
     return &this->response_trigger_;
   }
 
-  void play(const Ts &...x) override { this->send_or_resolve_(this->pdu_.value(x...)); }
+  void play(const Ts &...x) override { this->send_or_resolve_(this->pdu_.value(x...), this->command_options_(x...)); }
 
   void on_response(std::span<const uint8_t> request_pdu, std::span<const uint8_t> response_pdu) override {
     this->response_trigger_.trigger(request_pdu, response_pdu);
@@ -140,7 +161,8 @@ template<typename... Ts> class TypedClientActionBase : public ClientActionBase<T
 
 /// modbus_client.read_holding_registers / read_input_registers: on_response delivers the registers in
 /// host byte order as `values` (only valid for the duration of the trigger).
-template<typename... Ts> class ReadRegistersAction : public TypedClientActionBase<Ts...> {
+template<typename... Ts>
+class ReadRegistersAction : public TypedClientActionBase<Ts...>, public ReadCommandOptions<Ts...> {
  public:
   explicit ReadRegistersAction(bool holding) : holding_(holding) {}
   TEMPLATABLE_VALUE(uint16_t, start_address)
@@ -152,7 +174,8 @@ template<typename... Ts> class ReadRegistersAction : public TypedClientActionBas
     const auto function_code =
         this->holding_ ? modbus::FunctionCode::READ_HOLDING_REGISTERS : modbus::FunctionCode::READ_INPUT_REGISTERS;
     this->send_or_resolve_(
-        modbus::helpers::create_read_pdu(function_code, this->start_address_.value(x...), this->count_.value(x...)));
+        modbus::helpers::create_read_pdu(function_code, this->start_address_.value(x...), this->count_.value(x...)),
+        this->command_options_(x...));
   }
   void on_read_registers(modbus::EntityType entity_type, uint16_t start_address, std::span<const uint16_t> registers,
                          modbus::ResponseStatus status) override {
@@ -167,7 +190,7 @@ template<typename... Ts> class ReadRegistersAction : public TypedClientActionBas
 
 /// modbus_client.read_coils / read_discrete_inputs: on_response delivers the bits as a PackedBits view
 /// (bit 0 = the bit at start_address; only valid for the duration of the trigger).
-template<typename... Ts> class ReadBitsAction : public TypedClientActionBase<Ts...> {
+template<typename... Ts> class ReadBitsAction : public TypedClientActionBase<Ts...>, public ReadCommandOptions<Ts...> {
  public:
   explicit ReadBitsAction(bool coils) : coils_(coils) {}
   TEMPLATABLE_VALUE(uint16_t, start_address)
@@ -179,7 +202,8 @@ template<typename... Ts> class ReadBitsAction : public TypedClientActionBase<Ts.
     const auto function_code =
         this->coils_ ? modbus::FunctionCode::READ_COILS : modbus::FunctionCode::READ_DISCRETE_INPUTS;
     this->send_or_resolve_(
-        modbus::helpers::create_read_pdu(function_code, this->start_address_.value(x...), this->count_.value(x...)));
+        modbus::helpers::create_read_pdu(function_code, this->start_address_.value(x...), this->count_.value(x...)),
+        this->command_options_(x...));
   }
   void on_read_bits(modbus::EntityType entity_type, uint16_t start_address, modbus::PackedBits bits,
                     modbus::ResponseStatus status) override {

tests/component_tests/modbus_client/test_modbus_client.py

@@ -16,7 +16,13 @@ from esphome.components.modbus_client import (
     CONFIG_SCHEMA,
     MODBUS_CLIENT_SEND_SCHEMA,
 )
-from esphome.const import CONF_ADDRESS, CONF_ID, CONF_ON_ERROR, CONF_ON_RESPONSE
+from esphome.const import (
+    CONF_ADDRESS,
+    CONF_CONTINUOUS,
+    CONF_ID,
+    CONF_ON_ERROR,
+    CONF_ON_RESPONSE,
+)
 from esphome.core import Lambda
 from esphome.types import ConfigType
 
@@ -118,6 +124,29 @@ def test_on_no_response_retry_lambda_accepted() -> None:
     )
 
 
+def test_continuous_on_write_pdu_rejected() -> None:
+    """A literal write-code PDU with continuous: true is rejected at config time (reads only)."""
+    with pytest.raises(cv.Invalid, match="does not apply to a write PDU"):
+        MODBUS_CLIENT_SEND_SCHEMA(
+            {
+                CONF_ADDRESS: 0x01,
+                CONF_PDU: [0x06, 0x00, 0x01, 0x00, 0x0A],
+                CONF_CONTINUOUS: True,
+            }
+        )
+
+
+def test_continuous_on_read_pdu_accepted() -> None:
+    """A literal read-code PDU with continuous: true is fine - continuous polling applies to reads."""
+    MODBUS_CLIENT_SEND_SCHEMA(
+        {
+            CONF_ADDRESS: 0x01,
+            CONF_PDU: [0x03, 0x00, 0x10, 0x00, 0x01],
+            CONF_CONTINUOUS: True,
+        }
+    )
+
+
 # The standalone component block. The compile fixtures cover the accepted shapes end to end; these pin
 # the parts a fixture cannot express - a rejection, and a module flag whose absence breaks other
 # components rather than this one.

tests/components/modbus/modbus_client_hub_test.cpp

@@ -322,14 +322,14 @@ TEST(ModbusClientHubPriority, ContinuousReadRequeuesOnSuccessOnly) {
 
   device.read_holding_registers(0x100, 2, {.continuous = true});
   ASSERT_EQ(hub.queued_frames(), 1u);
-  EXPECT_TRUE(hub.queued(0).continuous);
+  EXPECT_TRUE(hub.queued(0).options.continuous);
   hub.force_send_next();
 
   // A matching successful response cycles the continuous entry back to READY.
   const uint8_t ok_response[] = {0x03, 0x04, 0x00, 0x2A, 0x01, 0x00};
   hub.receive_frame_for_test(0x02, ok_response);
   ASSERT_EQ(hub.queued_frames(), 1u);
-  EXPECT_TRUE(hub.queued(0).continuous);
+  EXPECT_TRUE(hub.queued(0).options.continuous);
 
   // An exception response ends the poll.
   hub.force_send_next();
@@ -346,13 +346,13 @@ TEST(ModbusClientHubPriority, RetriedContinuousReadStaysContinuous) {
 
   device.read_holding_registers(0x100, 2, {.continuous = true});
   ASSERT_EQ(hub.queued_frames(), 1u);
-  ASSERT_TRUE(hub.queued(0).continuous);
+  ASSERT_TRUE(hub.queued(0).options.continuous);
   hub.force_send_next();
 
   hub.timeout_waiting();  // no response -> device requests retry
 
   ASSERT_EQ(hub.queued_frames(), 1u);
-  EXPECT_TRUE(hub.queued(0).continuous);  // the retried poll stays continuous
+  EXPECT_TRUE(hub.queued(0).options.continuous);  // the retried poll stays continuous
 }
 
 // A one-shot duplicate downgrades a continuous poll to a one-shot (the mirror of a continuous
@@ -363,16 +363,16 @@ TEST(ModbusClientHubPriority, DuplicateSendDowngradesContinuous) {
 
   device.read_holding_registers(0x100, 2, {.continuous = true});
   ASSERT_EQ(hub.queued_frames(), 1u);
-  ASSERT_TRUE(hub.queued(0).continuous);
+  ASSERT_TRUE(hub.queued(0).options.continuous);
 
   device.read_holding_registers(0x100, 2);  // one-shot duplicate downgrades the poll
   ASSERT_EQ(hub.queued_frames(), 1u);
-  EXPECT_FALSE(hub.queued(0).continuous);
+  EXPECT_FALSE(hub.queued(0).options.continuous);
   EXPECT_EQ(hub.queued(0).pending, 1u);
 
   // It runs one more cycle to serve the request, then stops - not re-queued as a poll.
   hub.force_send_next();
-  EXPECT_FALSE(hub.waiting_command().continuous);
+  EXPECT_FALSE(hub.waiting_command().options.continuous);
   const uint8_t ok_response[] = {0x03, 0x04, 0x00, 0x2A, 0x01, 0x00};
   hub.receive_frame_for_test(0x02, ok_response);
   EXPECT_EQ(hub.queued_frames(), 0u);
@@ -407,16 +407,16 @@ TEST(ModbusClientHubPriority, DowngradeAfterTerminalKeepsRequestAlive) {
 
   device.read_holding_registers(0x100, 2, {.continuous = true});
   ASSERT_EQ(hub.queued_frames(), 1u);
-  ASSERT_TRUE(hub.queued(0).continuous);
+  ASSERT_TRUE(hub.queued(0).options.continuous);
 
   hub.force_send_next();
   const uint8_t exception_response[] = {0x83, 0x02};
   hub.receive_frame_for_test(0x02, exception_response);  // exception ends the poll; on_error re-sends
 
-  EXPECT_EQ(device.error_count_, 1);       // one terminal delivered so far
-  ASSERT_EQ(hub.queued_frames(), 1u);      // the re-send survived the sweep instead of being erased
-  EXPECT_FALSE(hub.queued(0).continuous);  // downgraded to a one-shot
-  EXPECT_EQ(hub.queued(0).pending, 1u);    // debt restored so the request runs
+  EXPECT_EQ(device.error_count_, 1);               // one terminal delivered so far
+  ASSERT_EQ(hub.queued_frames(), 1u);              // the re-send survived the sweep instead of being erased
+  EXPECT_FALSE(hub.queued(0).options.continuous);  // downgraded to a one-shot
+  EXPECT_EQ(hub.queued(0).pending, 1u);            // debt restored so the request runs
 
   // And it runs to its own terminal - a good response this time - then the entry is gone.
   hub.force_send_next();
@@ -434,18 +434,18 @@ TEST(ModbusClientHubPriority, ContinuousRequestUpgradesQueuedDuplicate) {
 
   device.read_holding_registers(0x100, 2);
   ASSERT_EQ(hub.queued_frames(), 1u);
-  ASSERT_FALSE(hub.queued(0).continuous);
+  ASSERT_FALSE(hub.queued(0).options.continuous);
 
   device.read_holding_registers(0x100, 2, {.continuous = true});
   ASSERT_EQ(hub.queued_frames(), 1u);
-  EXPECT_TRUE(hub.queued(0).continuous);
+  EXPECT_TRUE(hub.queued(0).options.continuous);
 
   // And it behaves as a poll from here: success cycles it back to READY.
   hub.force_send_next();
   const uint8_t ok_response[] = {0x03, 0x04, 0x00, 0x2A, 0x01, 0x00};
   hub.receive_frame_for_test(0x02, ok_response);
   ASSERT_EQ(hub.queued_frames(), 1u);
-  EXPECT_TRUE(hub.queued(0).continuous);
+  EXPECT_TRUE(hub.queued(0).options.continuous);
 }
 
 // The transmit order is one key with three levels: writes, then one-shot reads, then continuous
@@ -473,7 +473,7 @@ TEST(ModbusClientHubPriority, WritesThenOneShotReadsThenContinuousPolls) {
   EXPECT_EQ(hub.waiting_command().frame.pdu()[1], 0x02);  // then the one-shot read
   hub.timeout_waiting();
   hub.force_send_next();
-  EXPECT_TRUE(hub.waiting_command().continuous);  // and the poll takes what is left
+  EXPECT_TRUE(hub.waiting_command().options.continuous);  // and the poll takes what is left
 }
 
 // continuous is ignored for writes: the frame still sends at WRITE priority, once.
@@ -485,7 +485,7 @@ TEST(ModbusClientHubPriority, ContinuousIgnoredForWrites) {
   device.queue_pdu(write_pdu, {.continuous = true});
   ASSERT_EQ(hub.queued_frames(), 1u);
   EXPECT_EQ(hub.queued(0).priority(), CommandPriority::WRITE);
-  EXPECT_FALSE(hub.queued(0).continuous);
+  EXPECT_FALSE(hub.queued(0).options.continuous);
 }
 
 // A queued continuous poll does not count against immediate-send readiness: it ranks below every
@@ -496,7 +496,7 @@ TEST(ModbusClientHubPriority, ContinuousPollDoesNotBlockImmediateSend) {
 
   EXPECT_TRUE(hub.tx_buffer_empty());  // nothing queued
   device.read_holding_registers(0x100, 2, {.continuous = true});
-  ASSERT_TRUE(hub.queued(0).continuous);
+  ASSERT_TRUE(hub.queued(0).options.continuous);
   EXPECT_TRUE(hub.tx_buffer_empty());  // a READY continuous poll still leaves room to send now
 
   device.read_holding_registers(0x200, 2);  // a one-shot does count
@@ -1878,8 +1878,8 @@ TEST(ModbusClientHubPriority, ResendFromOnResponseAbsorbsIntoCompletingCommand)
   const uint8_t ok_response[] = {0x03, 0x04, 0x00, 0x2A, 0x01, 0x00};
   hub.receive_frame_for_test(0x02, ok_response);  // handler re-sends the identical frame mid-completion
 
-  ASSERT_EQ(hub.queued_frames(), 1u);      // absorbed into the same entry, not a fresh twin
-  EXPECT_FALSE(hub.queued(0).continuous);  // the one-shot re-send downgraded the poll
+  ASSERT_EQ(hub.queued_frames(), 1u);              // absorbed into the same entry, not a fresh twin
+  EXPECT_FALSE(hub.queued(0).options.continuous);  // the one-shot re-send downgraded the poll
 }
 
 // An exception-flagged function code is never silently re-sendable, even though the read check

tests/components/modbus_client/common.yaml

@@ -51,6 +51,7 @@ button:
       # A pdu lambda can hand-assemble bytes or return a modbus::helpers::create_*_pdu() builder result.
       - modbus_client.send:
           address: 0x01
+          continuous: true
           pdu: !lambda "return modbus::helpers::create_read_pdu(modbus::FunctionCode::READ_HOLDING_REGISTERS, 0x0010, 1);"
       - modbus_client.send:
           address: !lambda "return 1;"
@@ -91,6 +92,7 @@ button:
           address: !lambda "return 1;"
           start_address: 0x10
           count: 2
+          continuous: true
           on_response:
             then:
               - lambda: 'ESP_LOGI("modbus_client.test", "first=%u n=%u", values[0], (unsigned) values.size());'
@@ -98,6 +100,7 @@ button:
             then:
               - logger.log: "typed read timeout"
       - modbus_client.read_input_registers:
+          continuous: !lambda "return false;"
           address: 0x01
           start_address: 0x20
           on_custom_response:
@@ -113,12 +116,14 @@ button:
           address: 0x01
           start_address: 0x03
           count: 16
+          continuous: true
           on_response:
             then:
               - lambda: 'ESP_LOGI("modbus_client.test", "coil0=%d n=%u", bits[0], (unsigned) bits.size());'
       - modbus_client.read_discrete_inputs:
           address: 0x01
           start_address: 0x00
+          continuous: true
           on_error:
             then:
               - lambda: 'ESP_LOGW("modbus_client.test", "fc 0x%X exception %d", request.empty() ? 0 : request[0], (int) exception_code);'