[core] Deduplicate identical stateless lambdas to reduce flash usage (#11918)

tests/component_tests/text/test_text.py

@@ -1,4 +1,6 @@
-"""Tests for the binary sensor component."""
+"""Tests for the text component."""
+
+from esphome.core import CORE
 
 
 def test_text_is_setup(generate_main):
@@ -56,15 +58,22 @@ def test_text_config_value_mode_set(generate_main):
     assert "it_3->traits.set_mode(text::TEXT_MODE_PASSWORD);" in main_cpp
 
 
-def test_text_config_lamda_is_set(generate_main):
+def test_text_config_lambda_is_set(generate_main) -> None:
     """
-    Test if lambda is set for lambda mode (optimized with stateless lambda)
+    Test if lambda is set for lambda mode (optimized with stateless lambda and deduplication)
     """
     # Given
 
     # When
     main_cpp = generate_main("tests/component_tests/text/test_text.yaml")
 
+    # Get both global and main sections to find the shared lambda definition
+    full_cpp = CORE.cpp_global_section + main_cpp
+
     # Then
-    assert "it_4->set_template([]() -> esphome::optional<std::string> {" in main_cpp
-    assert 'return std::string{"Hello"};' in main_cpp
+    # Lambda is deduplicated into a shared function (reference in main section)
+    assert "it_4->set_template(shared_lambda_" in main_cpp
+    # Lambda body should be in the code somewhere
+    assert 'return std::string{"Hello"};' in full_cpp
+    # Verify the shared lambda function is defined (in global section)
+    assert "esphome::optional<std::string> shared_lambda_" in full_cpp

tests/unit_tests/test_lambda_dedup.py

@@ -0,0 +1,286 @@
+"""Tests for lambda deduplication in cpp_generator."""
+
+from esphome import cpp_generator as cg
+from esphome.core import CORE
+
+
+def test_deduplicate_identical_lambdas() -> None:
+    """Test that identical stateless lambdas are deduplicated."""
+    # Create two identical lambda expressions
+    lambda1 = cg.LambdaExpression(
+        parts=["return 42;"],
+        parameters=[],
+        capture="",
+        return_type=cg.RawExpression("int"),
+    )
+
+    lambda2 = cg.LambdaExpression(
+        parts=["return 42;"],
+        parameters=[],
+        capture="",
+        return_type=cg.RawExpression("int"),
+    )
+
+    # Try to deduplicate them
+    func_name1 = cg._get_shared_lambda_name(lambda1)
+    func_name2 = cg._get_shared_lambda_name(lambda2)
+
+    # Both should get the same function name (deduplication happened)
+    assert func_name1 == func_name2
+    assert func_name1 == "shared_lambda_0"
+
+
+def test_different_lambdas_not_deduplicated() -> None:
+    """Test that different lambdas get different function names."""
+    lambda1 = cg.LambdaExpression(
+        parts=["return 42;"],
+        parameters=[],
+        capture="",
+        return_type=cg.RawExpression("int"),
+    )
+
+    lambda2 = cg.LambdaExpression(
+        parts=["return 24;"],  # Different content
+        parameters=[],
+        capture="",
+        return_type=cg.RawExpression("int"),
+    )
+
+    func_name1 = cg._get_shared_lambda_name(lambda1)
+    func_name2 = cg._get_shared_lambda_name(lambda2)
+
+    # Different lambdas should get different function names
+    assert func_name1 != func_name2
+    assert func_name1 == "shared_lambda_0"
+    assert func_name2 == "shared_lambda_1"
+
+
+def test_different_return_types_not_deduplicated() -> None:
+    """Test that lambdas with different return types are not deduplicated."""
+    lambda1 = cg.LambdaExpression(
+        parts=["return 42;"],
+        parameters=[],
+        capture="",
+        return_type=cg.RawExpression("int"),
+    )
+
+    lambda2 = cg.LambdaExpression(
+        parts=["return 42;"],  # Same content
+        parameters=[],
+        capture="",
+        return_type=cg.RawExpression("float"),  # Different return type
+    )
+
+    func_name1 = cg._get_shared_lambda_name(lambda1)
+    func_name2 = cg._get_shared_lambda_name(lambda2)
+
+    # Different return types = different functions
+    assert func_name1 != func_name2
+
+
+def test_different_parameters_not_deduplicated() -> None:
+    """Test that lambdas with different parameters are not deduplicated."""
+    lambda1 = cg.LambdaExpression(
+        parts=["return x;"],
+        parameters=[("int", "x")],
+        capture="",
+        return_type=cg.RawExpression("int"),
+    )
+
+    lambda2 = cg.LambdaExpression(
+        parts=["return x;"],  # Same content
+        parameters=[("float", "x")],  # Different parameter type
+        capture="",
+        return_type=cg.RawExpression("int"),
+    )
+
+    func_name1 = cg._get_shared_lambda_name(lambda1)
+    func_name2 = cg._get_shared_lambda_name(lambda2)
+
+    # Different parameters = different functions
+    assert func_name1 != func_name2
+
+
+def test_flush_lambda_dedup_declarations() -> None:
+    """Test that deferred declarations are properly stored for later flushing."""
+    # Create a lambda which will create a deferred declaration
+    lambda1 = cg.LambdaExpression(
+        parts=["return 42;"],
+        parameters=[],
+        capture="",
+        return_type=cg.RawExpression("int"),
+    )
+
+    cg._get_shared_lambda_name(lambda1)
+
+    # Check that declaration was stored
+    assert cg._KEY_LAMBDA_DEDUP_DECLARATIONS in CORE.data
+    assert len(CORE.data[cg._KEY_LAMBDA_DEDUP_DECLARATIONS]) == 1
+
+    # Verify the declaration content is correct
+    declaration = CORE.data[cg._KEY_LAMBDA_DEDUP_DECLARATIONS][0]
+    assert "shared_lambda_0" in declaration
+    assert "return 42;" in declaration
+
+    # Note: The actual flushing happens via CORE.add_job with FINAL priority
+    # during real code generation, so we don't test that here
+
+
+def test_shared_function_lambda_expression() -> None:
+    """Test SharedFunctionLambdaExpression behaves correctly."""
+    shared_lambda = cg.SharedFunctionLambdaExpression(
+        func_name="shared_lambda_0",
+        parameters=[],
+        return_type=cg.RawExpression("int"),
+    )
+
+    # Should output just the function name
+    assert str(shared_lambda) == "shared_lambda_0"
+
+    # Should have empty capture (stateless)
+    assert shared_lambda.capture == ""
+
+    # Should have empty content (just a reference)
+    assert shared_lambda.content == ""
+
+
+def test_lambda_deduplication_counter() -> None:
+    """Test that lambda counter increments correctly."""
+    # Create 3 different lambdas
+    for i in range(3):
+        lambda_expr = cg.LambdaExpression(
+            parts=[f"return {i};"],
+            parameters=[],
+            capture="",
+            return_type=cg.RawExpression("int"),
+        )
+        func_name = cg._get_shared_lambda_name(lambda_expr)
+        assert func_name == f"shared_lambda_{i}"
+
+
+def test_lambda_format_body() -> None:
+    """Test that format_body correctly formats lambda body with source."""
+    # Without source
+    lambda1 = cg.LambdaExpression(
+        parts=["return 42;"],
+        parameters=[],
+        capture="",
+        return_type=None,
+        source=None,
+    )
+    assert lambda1.format_body() == "return 42;"
+
+    # With source would need a proper source object, skip for now
+
+
+def test_stateful_lambdas_not_deduplicated() -> None:
+    """Test that stateful lambdas (non-empty capture) are not deduplicated."""
+    # _get_shared_lambda_name is only called for stateless lambdas (capture == "")
+    # Stateful lambdas bypass deduplication entirely in process_lambda
+
+    # Verify that a stateful lambda would NOT get deduplicated
+    # by checking it's not in the stateless dedup cache
+    stateful_lambda = cg.LambdaExpression(
+        parts=["return x + y;"],
+        parameters=[],
+        capture="=",  # Non-empty capture means stateful
+        return_type=cg.RawExpression("int"),
+    )
+
+    # Stateful lambdas should NOT be passed to _get_shared_lambda_name
+    # This is enforced by the `if capture == ""` check in process_lambda
+    # We verify the lambda has a non-empty capture
+    assert stateful_lambda.capture != ""
+    assert stateful_lambda.capture == "="
+
+
+def test_static_variable_detection() -> None:
+    """Test detection of static variables in lambda code."""
+    # Should detect static variables
+    assert cg._has_static_variables("static int counter = 0;")
+    assert cg._has_static_variables("static bool flag = false; return flag;")
+    assert cg._has_static_variables("  static  float  value  =  1.0;  ")
+
+    # Should NOT detect static_cast, static_assert, etc. (with underscores)
+    assert not cg._has_static_variables("return static_cast<int>(value);")
+    assert not cg._has_static_variables("static_assert(sizeof(int) == 4);")
+    assert not cg._has_static_variables("auto ptr = static_pointer_cast<Foo>(bar);")
+
+    # Edge case: 'cast', 'assert', 'pointer_cast' are NOT C++ keywords
+    # Someone could use them as type names, but we should NOT flag them
+    # because they're not actually static variables with state
+    # NOTE: These are valid C++ but extremely unlikely in ESPHome lambdas
+    assert not cg._has_static_variables("static cast obj;")  # 'cast' as type name
+    assert not cg._has_static_variables("static assert value;")  # 'assert' as type name
+    assert not cg._has_static_variables(
+        "static pointer_cast ptr;"
+    )  # 'pointer_cast' as type
+
+    # Should NOT detect in comments
+    assert not cg._has_static_variables("// static int x = 0;\nreturn 42;")
+    assert not cg._has_static_variables("/* static int y = 0; */ return 42;")
+
+    # Should detect even with comments elsewhere
+    assert cg._has_static_variables("// comment\nstatic int x = 0;\nreturn x;")
+
+    # Should NOT detect non-static code
+    assert not cg._has_static_variables("int counter = 0; return counter++;")
+    assert not cg._has_static_variables("return 42;")
+
+    # Should handle newlines between static and type/variable
+    assert cg._has_static_variables("static int\nfoo = 0;")
+    assert cg._has_static_variables("static\nint\nbar = 0;")
+    assert cg._has_static_variables(
+        "static  int  \n  foo  =  0;"
+    )  # Mixed spaces/newlines
+
+
+def test_lambdas_with_static_not_deduplicated() -> None:
+    """Test that lambdas with static variables are not deduplicated."""
+    # Two identical lambdas with static variables
+    lambda1 = cg.LambdaExpression(
+        parts=["static int counter = 0; return counter++;"],
+        parameters=[],
+        capture="",
+        return_type=cg.RawExpression("int"),
+    )
+
+    lambda2 = cg.LambdaExpression(
+        parts=["static int counter = 0; return counter++;"],
+        parameters=[],
+        capture="",
+        return_type=cg.RawExpression("int"),
+    )
+
+    # Should return None (not deduplicated)
+    func_name1 = cg._get_shared_lambda_name(lambda1)
+    func_name2 = cg._get_shared_lambda_name(lambda2)
+
+    assert func_name1 is None
+    assert func_name2 is None
+
+
+def test_lambdas_without_static_still_deduplicated() -> None:
+    """Test that lambdas without static variables are still deduplicated."""
+    # Two identical lambdas WITHOUT static variables
+    lambda1 = cg.LambdaExpression(
+        parts=["int counter = 0; return counter++;"],  # No static
+        parameters=[],
+        capture="",
+        return_type=cg.RawExpression("int"),
+    )
+
+    lambda2 = cg.LambdaExpression(
+        parts=["int counter = 0; return counter++;"],  # No static
+        parameters=[],
+        capture="",
+        return_type=cg.RawExpression("int"),
+    )
+
+    # Should be deduplicated (same function name)
+    func_name1 = cg._get_shared_lambda_name(lambda1)
+    func_name2 = cg._get_shared_lambda_name(lambda2)
+
+    assert func_name1 is not None
+    assert func_name2 is not None
+    assert func_name1 == func_name2