Packages feature (#1052)

* Started to work on packages feature

* Added some more validation to packages config

* Fixed some linter warnings

* Updated tests

* Reordered consts to avoid linter error

* Reordered consts to avoid linter error

* Refactored test yaml files to integrate into existing test pipeline

Co-authored-by: Dmitry Berezovsky <dmitry.berezovsky@logicify.com>

esphome/components/packages/__init__.py

@@ -0,0 +1,51 @@
+from deepmerge import conservative_merger as package_merger
+
+import esphome.config_validation as cv
+
+from esphome.const import CONF_PACKAGES
+
+VALID_PACKAGE_NAME_CHARS = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789_'
+
+
+def _merge_package(config, package_name, package_config):
+    config = config.copy()
+    package_merger.merge(config, package_config)
+    return config
+
+
+def _is_valid_package_name(value: str) -> bool:
+    if not value:
+        return False
+    if value[0].isdigit():
+        return False
+    try:
+        cv.valid_name(value)
+    except cv.Invalid:
+        return False
+    return True
+
+
+def do_packages_pass(config: dict):
+    if CONF_PACKAGES not in config:
+        return
+    packages = config[CONF_PACKAGES]
+    temp_config = config.copy()
+    with cv.prepend_path(CONF_PACKAGES):
+        if packages is not None and not isinstance(packages, dict):
+            raise cv.Invalid("Packages must be a key to value mapping, got {} instead"
+                             "".format(type(packages)))
+        for package_name, package_config in packages.items():
+            with cv.prepend_path(package_name):
+                if not isinstance(package_config, dict):
+                    raise cv.Invalid("Package definition must be a dictionary containing valid "
+                                     "esphome configuration to be merged with the main "
+                                     "config, got {} instead"
+                                     .format(type(package_config)))
+                if not _is_valid_package_name(package_name):
+                    raise cv.Invalid("Package name is invalid. Valid name should consist of "
+                                     "letters, numbers and underscores. It shouldn't also "
+                                     "start with number")
+                temp_config = _merge_package(temp_config, package_name, package_config)
+        del temp_config[CONF_PACKAGES]
+        config.clear()
+        config.update(temp_config)