[core] Use begin/end marker pairs around each component's IIFE

Rename the bracket markers from "// === X ===" (same on both sides)
to "// === begin X ===" and "// === end X ===" so the generated
main.cpp reads unambiguously when scanning by component. Comment-only
components still get a single "begin X" marker since they have no
IIFE to close.

esphome/core/__init__.py

@@ -1052,15 +1052,15 @@ class EsphomeCore:
 
         # Split main_statements at ComponentMarker sentinels into a prefix
         # (statements emitted before any component) plus per-component groups.
-        # Each group's first entry is its marker comment, kept separate so
-        # it can bracket the IIFE rather than be buried inside it.
+        # Each group carries its component name so cpp_main_section can emit
+        # begin/end marker comments bracketing the IIFE.
         prefix: list[str] = []
         components: list[tuple[str, list[str]]] = []
         current = prefix
         for exp in self.main_statements:
             if isinstance(exp, ComponentMarker):
                 body: list[str] = []
-                components.append((str(exp).rstrip(), body))
+                components.append((exp.name, body))
                 current = body
                 continue
             current.append(str(statement(exp)).rstrip())
@@ -1072,16 +1072,18 @@ class EsphomeCore:
         # Each component's block is wrapped in IIFE lambdas so its stack
         # frame is released on return, bounding peak stack during setup().
         # Large blocks are sub-split to cap single heavy components (e.g.
-        # sensor platforms with many filter registrations). The marker
-        # comment brackets the IIFE on both sides so the generated
-        # main.cpp is easy to scan by component.
+        # sensor platforms with many filter registrations). "begin X" and
+        # "end X" marker comments bracket the IIFE so the generated
+        # main.cpp is easy to scan by component; a comment-only component
+        # gets a single "begin X" marker (no IIFE, no end marker).
         pieces = list(prefix)
-        for marker, body in components:
+        for name, body in components:
             wrapped = _wrap_in_iifes(body, max_statements=50)
-            pieces.append(marker)
+            has_iife = any("[]()" in line for line in wrapped)
+            pieces.append(f"// === begin {name} ===")
             pieces.extend(wrapped)
-            if any("[]()" in line for line in wrapped):
-                pieces.append(marker)
+            if has_iife:
+                pieces.append(f"// === end {name} ===")
         return "\n".join(pieces) + "\n\n"
 
     @property

esphome/cpp_generator.py

@@ -436,9 +436,8 @@ class LineComment(Statement):
 
 class ComponentMarker(Statement):
     """Sentinel marker recorded in main_statements when a component's
-    to_code begins emitting code. Used by cpp_main_section to split
-    setup() output into per-component chunks, so each component's
-    stack frame is released on return."""
+    to_code begins emitting code. ``cpp_main_section`` consumes these
+    to bracket each component's IIFE with begin/end comment markers."""
 
     __slots__ = ("name",)
 
@@ -446,7 +445,7 @@ class ComponentMarker(Statement):
         self.name = name
 
     def __str__(self):
-        return f"// === {self.name} ==="
+        return f"// === begin {self.name} ==="
 
 
 class ProgmemAssignmentExpression(AssignmentExpression):

tests/unit_tests/test_core.py

@@ -937,7 +937,7 @@ def test_wrap_in_iifes_unbalanced_braces_fall_through() -> None:
 def test_wrap_in_iifes_skips_comment_only_chunks() -> None:
     # Components that emit only a ComponentMarker + config dump (no C++
     # statements) should not be wrapped in an empty IIFE.
-    lines = ["// === sha256 ===", "// sha256:", "//   {}"]
+    lines = ["// === begin sha256 ===", "// sha256:", "//   {}"]
     assert core._wrap_in_iifes(lines, max_statements=50) == lines
 
 
@@ -961,14 +961,16 @@ def test_cpp_main_section_component_marker_wraps_in_iife() -> None:
     out = target.cpp_main_section
     assert out.count("[]() {") == 2
     assert out.count("}();") == 2
-    # Each component's marker brackets its IIFE (once before, once after).
-    assert out.count("// === logger ===") == 2
-    assert out.count("// === wifi ===") == 2
+    # Each component's IIFE is bracketed by a begin/end marker pair.
+    assert "// === begin logger ===" in out
+    assert "// === end logger ===" in out
+    assert "// === begin wifi ===" in out
+    assert "// === end wifi ===" in out
 
 
 def test_cpp_main_section_comment_only_component_emits_single_marker() -> None:
     # A component that emits no C++ statements (only a ComponentMarker)
-    # should not grow a useless trailing duplicate marker.
+    # gets only a begin marker — no IIFE, so no end marker.
     target = core.EsphomeCore()
     target.main_statements = [
         ComponentMarker("sha256"),
@@ -976,8 +978,10 @@ def test_cpp_main_section_comment_only_component_emits_single_marker() -> None:
         RawStatement("new_wifi();"),
     ]
     out = target.cpp_main_section
-    assert out.count("// === sha256 ===") == 1
-    assert out.count("// === wifi ===") == 2  # wifi has an IIFE
+    assert "// === begin sha256 ===" in out
+    assert "// === end sha256 ===" not in out
+    assert "// === begin wifi ===" in out
+    assert "// === end wifi ===" in out
 
 
 def test_cpp_main_section_prefix_statements_stay_outside_iife() -> None: