ESPHome Development Assistant

Expert assistant for ESPHome - a system to configure microcontrollers (ESP32, ESP8266, RP2040, LibreTiny chips) using YAML configuration files that generate C++ firmware for home automation.

Project Context

Architecture

Code-generation architecture: Python parses YAML → generates C++ → PlatformIO compiles → flash to device

**Directory Structure:**

**Core Systems:**

1. **Configuration** (`esphome/config*.py`) - YAML parsing/validation with Voluptuous

2. **Code Generation** (`esphome/codegen.py`, `esphome/cpp_generator.py`) - Python → C++ conversion

3. **Component System** (`esphome/components/`) - Modular platform-specific implementations

4. **Core Framework** (`esphome/core/`) - Lifecycle, hardware abstraction, registration

5. **Dashboard** (`esphome/dashboard/`) - Web UI for device management

**Supported Platforms:**

Code Style Requirements

Python

C++

- Functions/methods/variables: `lower_snake_case`

- Classes/structs/enums: `UpperCamelCase`

- Top-level constants: `UPPER_SNAKE_CASE`

- Function-local constants: `lower_snake_case`

- Protected/private fields: `lower_snake_case_with_trailing_underscore_`

Field Visibility Rules

1. Pointer lifetime issues (setters validate/store from known lists)

2. Invariant coupling (fields must stay synchronized)

3. Resource management (setters perform cleanup/registration)

Preprocessor Usage

- Conditional compilation (`#ifdef`, `#ifndef`)

- Compile-time sizes from Python codegen (e.g., `cg.add_define()` for `std::array` dimensions)

Component Development Pattern

Standard Component Structure

```

components/[component_name]/

├── __init__.py # Schema & code generation

├── [component].h # C++ header

├── [component].cpp # C++ implementation

└── [platform]/ # Platform-specific code

├── __init__.py

├── [platform].h

└── [platform].cpp

```

Component Metadata

```python

DEPENDENCIES = ["required_component"]

AUTO_LOAD = ["auto_loaded_component"]

CONFLICTS_WITH = ["incompatible_component"]

CODEOWNERS = ["@github_username"]

MULTI_CONF = True # Allow multiple instances

```

Configuration Schema Pattern

```python

import esphome.codegen as cg

import esphome.config_validation as cv

from esphome.const import CONF_KEY, CONF_ID

CONF_PARAM = "param" # New constant not in esphome/const.py

my_component_ns = cg.esphome_ns.namespace("my_component")

MyComponent = my_component_ns.class_("MyComponent", cg.Component)

CONFIG_SCHEMA = cv.Schema({

cv.GenerateID(): cv.declare_id(MyComponent),

cv.Required(CONF_KEY): cv.string,

cv.Optional(CONF_PARAM, default=42): cv.int_,

}).extend(cv.COMPONENT_SCHEMA)

async def to_code(config):

var = cg.new_Pvariable(config[CONF_ID])

await cg.register_component(var, config)

cg.add(var.set_key(config[CONF_KEY]))

cg.add(var.set_param(config[CONF_PARAM]))

```

C++ Class Pattern

```cpp

namespace esphome::my_component {

class MyComponent : public Component {

public:

void setup() override;

void loop() override;

void dump_config() override;

void set_key(const std::string &key) { this->key_ = key; }

void set_param(int param) { this->param_ = param; }

protected:

std::string key_;

int param_{0};

};

} // namespace esphome::my_component

```

Common Component Types

Sensor Component

```python

from esphome.components import sensor

CONFIG_SCHEMA = sensor.sensor_schema(MySensor).extend(cv.polling_component_schema("60s"))

async def to_code(config):

var = await sensor.new_sensor(config)

await cg.register_component(var, config)

```

Binary Sensor Component

```python

from esphome.components import binary_sensor

CONFIG_SCHEMA = binary_sensor.binary_sensor_schema().extend({ ... })

async def to_code(config):

var = await binary_sensor.new_binary_sensor(config)

```

Switch Component

```python

from esphome.components import switch

CONFIG_SCHEMA = switch.switch_schema().extend({ ... })

async def to_code(config):

var = await switch.new_switch(config)

```

Configuration Validation

Common Validators

Platform/Framework Constraints

Schema Extensions

```python

CONFIG_SCHEMA = cv.Schema({ ... })

.extend(cv.COMPONENT_SCHEMA)

.extend(uart.UART_DEVICE_SCHEMA)

.extend(i2c.i2c_device_schema(0x48))

.extend(spi.spi_device_schema(cs_pin_required=True))

```

Development Workflow

Environment Setup

Running Commands

Execute within project environment:

```bash

python3 script/run-in-env.py <command>

python3 script/run-in-env.py pre-commit run

```

Testing

**Python Tests:**

```bash

pytest

```

**C++ Static Analysis:**

```bash

clang-tidy

```

**Component Tests:**

```bash

Test specific component

./script/test_build_components -c <component>

Test specific platform

./script/test_build_components -t <target>

Test all components together (catch ID conflicts)

./script/test_component_grouping.py -e config --all

```

**YAML test files** located in:

Key Configuration Files

Instructions for AI Assistant

When working on ESPHome:

1. **Always prefix member access** with `this->` in C++ code

2. **Use `protected` fields by default**, only `private` when safety-critical (document why)

3. **Avoid `#define` for constants** - use `const` or enums

4. **Add new defines to `esphome/core/defines.h`** for static analysis

5. **Follow component structure** with `__init__.py` for schema and separate C++ files

6. **Extend appropriate schemas** (sensor, binary_sensor, switch, etc.)

7. **Use platform validators** to restrict components to compatible platforms

8. **Test component integration** with `test_component_grouping.py --all` before finalizing

9. **Run formatters** (`ruff`, `clang-format`) and linters (`flake8`, `clang-tidy`)

10. **Document metadata** (DEPENDENCIES, CODEOWNERS, CONFLICTS_WITH) in component `__init__.py`