codegen: Lambda improvements (#1476)

* Use #line directives in generated C++ code for lambdas

The #line directive in gcc is meant specifically for pieces of imported
code included in generated code, exactly what happens with lambdas in
the yaml files: https://gcc.gnu.org/onlinedocs/cpp/Line-Control.html

With this change, if I add the following at line 165 of kithen.yaml:
    - lambda: undefined_var == 5;

then "$ esphome kitchen.yaml compile" shows the following:

INFO Reading configuration kitchen.yaml...
INFO Generating C++ source...
INFO Compiling app...
INFO Running:  platformio run -d kitchen
<...>
Compiling .pioenvs/kitchen/src/main.cpp.o
kitchen.yaml: In lambda function:
kitchen.yaml:165:7: error: 'undefined_var' was not declared in this scope
*** [.pioenvs/kitchen/src/main.cpp.o] Error 1
== [FAILED] Took 2.37 seconds ==

* Silence gcc warning on multiline macros in lambdas

When the \ is used at the end of the C++ source in a lambda (line
continuation, often used in preprocessor macros), esphome will copy that
into main.cpp once as code and once as a // commment.  gcc will complain
about the multiline commment:

Compiling .pioenvs/kitchen/src/main.cpp.o
kitchen.yaml:640:3: warning: multi-line comment [-Wcomment]

Try to replace the \ with a "<cont>" for lack of a better idea.

esphome/config_validation.py

@@ -17,9 +17,10 @@ from esphome.const import ALLOWED_NAME_CHARS, CONF_AVAILABILITY, CONF_COMMAND_TO
     CONF_HOUR, CONF_MINUTE, CONF_SECOND, CONF_VALUE, CONF_UPDATE_INTERVAL, CONF_TYPE_ID, \
     CONF_TYPE, CONF_PACKAGES
 from esphome.core import CORE, HexInt, IPAddress, Lambda, TimePeriod, TimePeriodMicroseconds, \
-    TimePeriodMilliseconds, TimePeriodSeconds, TimePeriodMinutes
+    TimePeriodMilliseconds, TimePeriodSeconds, TimePeriodMinutes, DocumentLocation
 from esphome.helpers import list_starts_with, add_class_to_obj
 from esphome.voluptuous_schema import _Schema
+from esphome.yaml_util import ESPHomeDataBase
 
 _LOGGER = logging.getLogger(__name__)
 
@@ -982,7 +983,11 @@ LAMBDA_ENTITY_ID_PROG = re.compile(r'id\(\s*([a-zA-Z0-9_]+\.[.a-zA-Z0-9_]+)\s*\)
 def lambda_(value):
     """Coerce this configuration option to a lambda."""
     if not isinstance(value, Lambda):
-        value = Lambda(string_strict(value))
+        start_mark = None
+        if isinstance(value, ESPHomeDataBase) and value.esp_range is not None:
+            start_mark = DocumentLocation.copy(value.esp_range.start_mark)
+            start_mark.line += value.content_offset
+        value = Lambda(string_strict(value), start_mark)
     entity_id_parts = re.split(LAMBDA_ENTITY_ID_PROG, value.value)
     if len(entity_id_parts) != 1:
         entity_ids = ' '.join("'{}'".format(entity_id_parts[i])

esphome/core.py

@@ -227,7 +227,7 @@ LAMBDA_PROG = re.compile(r'id\(\s*([a-zA-Z_][a-zA-Z0-9_]*)\s*\)(\.?)')
 
 
 class Lambda:
-    def __init__(self, value):
+    def __init__(self, value, start_mark=None):
         # pylint: disable=protected-access
         if isinstance(value, Lambda):
             self._value = value._value
@@ -235,6 +235,7 @@ class Lambda:
             self._value = value
         self._parts = None
         self._requires_ids = None
+        self._source_location = start_mark
 
     # https://stackoverflow.com/a/241506/229052
     def comment_remover(self, text):
@@ -277,6 +278,10 @@ class Lambda:
     def __repr__(self):
         return f'Lambda<{self.value}>'
 
+    @property
+    def source_location(self):
+        return self._source_location
+
 
 class ID:
     def __init__(self, id, is_declaration=False, type=None, is_manual=None):
@@ -334,9 +339,21 @@ class DocumentLocation:
             mark.column
         )
 
+    @classmethod
+    def copy(cls, location):
+        return cls(
+            location.document,
+            location.line,
+            location.column
+        )
+
     def __str__(self):
         return f'{self.document} {self.line}:{self.column}'
 
+    @property
+    def as_line_directive(self):
+        return f'#line {self.line + 1} "{self.document}"'
+
 
 class DocumentRange:
     def __init__(self, start_mark: DocumentLocation, end_mark: DocumentLocation):

esphome/cpp_generator.py

@@ -1,6 +1,7 @@
 import abc
 import inspect
 import math
+import re
 
 # pylint: disable=unused-import, wrong-import-order
 from typing import Any, Generator, List, Optional, Tuple, Type, Union, Sequence
@@ -188,13 +189,14 @@ class ParameterListExpression(Expression):
 
 
 class LambdaExpression(Expression):
-    __slots__ = ("parts", "parameters", "capture", "return_type")
+    __slots__ = ("parts", "parameters", "capture", "return_type", "source")
 
-    def __init__(self, parts, parameters, capture: str = '=', return_type=None):
+    def __init__(self, parts, parameters, capture: str = '=', return_type=None, source=None):
         self.parts = parts
         if not isinstance(parameters, ParameterListExpression):
             parameters = ParameterListExpression(*parameters)
         self.parameters = parameters
+        self.source = source
         self.capture = capture
         self.return_type = safe_exp(return_type) if return_type is not None else None
 
@@ -202,7 +204,10 @@ class LambdaExpression(Expression):
         cpp = f'[{self.capture}]({self.parameters})'
         if self.return_type is not None:
             cpp += f' -> {self.return_type}'
-        cpp += f' {{\n{self.content}\n}}'
+        cpp += ' {\n'
+        if self.source is not None:
+            cpp += f'{self.source.as_line_directive}\n'
+        cpp += f'{self.content}\n}}'
         return indent_all_but_first_and_last(cpp)
 
     @property
@@ -360,7 +365,7 @@ class LineComment(Statement):
         self.value = value
 
     def __str__(self):
-        parts = self.value.split('\n')
+        parts = re.sub(r'\\\s*\n', r'<cont>\n', self.value, re.MULTILINE).split('\n')
         parts = [f'// {x}' for x in parts]
         return '\n'.join(parts)
 
@@ -555,7 +560,7 @@ def process_lambda(
         else:
             parts[i * 3 + 1] = var
         parts[i * 3 + 2] = ''
-    yield LambdaExpression(parts, parameters, capture, return_type)
+    yield LambdaExpression(parts, parameters, capture, return_type, value.source_location)
 
 
 def is_template(value):

esphome/yaml_util.py

@@ -11,7 +11,8 @@ import yaml.constructor
 
 from esphome import core
 from esphome.config_helpers import read_config_file
-from esphome.core import EsphomeError, IPAddress, Lambda, MACAddress, TimePeriod, DocumentRange
+from esphome.core import EsphomeError, IPAddress, Lambda, MACAddress, TimePeriod, \
+    DocumentRange, DocumentLocation
 from esphome.helpers import add_class_to_obj
 from esphome.util import OrderedDict, filter_yaml_files
 
@@ -30,9 +31,16 @@ class ESPHomeDataBase:
     def esp_range(self):
         return getattr(self, '_esp_range', None)
 
+    @property
+    def content_offset(self):
+        return getattr(self, '_content_offset', 0)
+
     def from_node(self, node):
         # pylint: disable=attribute-defined-outside-init
         self._esp_range = DocumentRange.from_marks(node.start_mark, node.end_mark)
+        if isinstance(node, yaml.ScalarNode):
+            if node.style is not None and node.style in '|>':
+                self._content_offset = 1
 
 
 class ESPForceValue:
@@ -257,7 +265,10 @@ class ESPHomeLoader(yaml.SafeLoader):  # pylint: disable=too-many-ancestors
 
     @_add_data_ref
     def construct_lambda(self, node):
-        return Lambda(str(node.value))
+        start_mark = DocumentLocation.from_mark(node.start_mark)
+        if node.style is not None and node.style in '|>':
+            start_mark.line += 1
+        return Lambda(str(node.value), start_mark)
 
     @_add_data_ref
     def construct_force(self, node):