Support nil pointers to structs in properties

Allow primary builders to reduce allocations of empty structures by
allowing nil pointers to concrete struct types.  Property readers will
not recurse into nil pointers, property writers will replace the nil
pointer with a pointer to the zero value of the pointer element type.

Allows a >50% primary builder time improvement with a trivial change in
Soong.

Change-Id: If6ad674bf7bf2a694c335378a074643a97d3c50b

1 files changed, 198 insertions, 136 deletions

diff --git a/unpack_test.go b/unpack_test.go
index 7b314dd..ea4dbc7 100644
--- a/unpack_test.go
+++ b/unpack_test.go
@@ -28,15 +28,17 @@ import (
 var validUnpackTestCases = []struct {
 	input  string
 	output []interface{}
+	empty  []interface{}
 	errs   []error
 }{
-	{`
-		m {
-			name: "abc",
-			blank: "",
-		}
+	{
+		input: `
+			m {
+				name: "abc",
+				blank: "",
+			}
 		`,
-		[]interface{}{
+		output: []interface{}{
 			struct {
 				Name  *string
 				Blank *string
@@ -47,46 +49,46 @@ var validUnpackTestCases = []struct {
 				Unset: nil,
 			},
 		},
-		nil,
 	},
 
-	{`
-		m {
-			name: "abc",
-		}
+	{
+		input: `
+			m {
+				name: "abc",
+			}
 		`,
-		[]interface{}{
+		output: []interface{}{
 			struct {
 				Name string
 			}{
 				Name: "abc",
 			},
 		},
-		nil,
 	},
 
-	{`
-		m {
-			isGood: true,
-		}
+	{
+		input: `
+			m {
+				isGood: true,
+			}
 		`,
-		[]interface{}{
+		output: []interface{}{
 			struct {
 				IsGood bool
 			}{
 				IsGood: true,
 			},
 		},
-		nil,
 	},
 
-	{`
-		m {
-			isGood: true,
-			isBad: false,
-		}
+	{
+		input: `
+			m {
+				isGood: true,
+				isBad: false,
+			}
 		`,
-		[]interface{}{
+		output: []interface{}{
 			struct {
 				IsGood *bool
 				IsBad  *bool
@@ -97,17 +99,17 @@ var validUnpackTestCases = []struct {
 				IsUgly: nil,
 			},
 		},
-		nil,
 	},
 
-	{`
-		m {
-			stuff: ["asdf", "jkl;", "qwert",
-				"uiop", "bnm,"],
-			empty: []
-		}
+	{
+		input: `
+			m {
+				stuff: ["asdf", "jkl;", "qwert",
+					"uiop", "bnm,"],
+				empty: []
+			}
 		`,
-		[]interface{}{
+		output: []interface{}{
 			struct {
 				Stuff []string
 				Empty []string
@@ -118,17 +120,17 @@ var validUnpackTestCases = []struct {
 				Nil:   nil,
 			},
 		},
-		nil,
 	},
 
-	{`
-		m {
-			nested: {
-				name: "abc",
+	{
+		input: `
+			m {
+				nested: {
+					name: "abc",
+				}
 			}
-		}
 		`,
-		[]interface{}{
+		output: []interface{}{
 			struct {
 				Nested struct {
 					Name string
@@ -139,17 +141,17 @@ var validUnpackTestCases = []struct {
 				},
 			},
 		},
-		nil,
 	},
 
-	{`
-		m {
-			nested: {
-				name: "def",
+	{
+		input: `
+			m {
+				nested: {
+					name: "def",
+				}
 			}
-		}
 		`,
-		[]interface{}{
+		output: []interface{}{
 			struct {
 				Nested interface{}
 			}{
@@ -158,19 +160,19 @@ var validUnpackTestCases = []struct {
 				},
 			},
 		},
-		nil,
 	},
 
-	{`
-		m {
-			nested: {
-				foo: "abc",
-			},
-			bar: false,
-			baz: ["def", "ghi"],
-		}
+	{
+		input: `
+			m {
+				nested: {
+					foo: "abc",
+				},
+				bar: false,
+				baz: ["def", "ghi"],
+			}
 		`,
-		[]interface{}{
+		output: []interface{}{
 			struct {
 				Nested struct {
 					Foo string
@@ -185,19 +187,19 @@ var validUnpackTestCases = []struct {
 				Baz: []string{"def", "ghi"},
 			},
 		},
-		nil,
 	},
 
-	{`
-		m {
-			nested: {
-				foo: "abc",
-			},
-			bar: false,
-			baz: ["def", "ghi"],
-		}
+	{
+		input: `
+			m {
+				nested: {
+					foo: "abc",
+				},
+				bar: false,
+				baz: ["def", "ghi"],
+			}
 		`,
-		[]interface{}{
+		output: []interface{}{
 			struct {
 				Nested struct {
 					Foo string `allowNested:"true"`
@@ -214,19 +216,19 @@ var validUnpackTestCases = []struct {
 				Baz: []string{"def", "ghi"},
 			},
 		},
-		nil,
 	},
 
-	{`
-		m {
-			nested: {
-				foo: "abc",
-			},
-			bar: false,
-			baz: ["def", "ghi"],
-		}
+	{
+		input: `
+			m {
+				nested: {
+					foo: "abc",
+				},
+				bar: false,
+				baz: ["def", "ghi"],
+			}
 		`,
-		[]interface{}{
+		output: []interface{}{
 			struct {
 				Nested struct {
 					Foo string
@@ -241,24 +243,25 @@ var validUnpackTestCases = []struct {
 				Baz: []string{"def", "ghi"},
 			},
 		},
-		[]error{
+		errs: []error{
 			&Error{
 				Err: fmt.Errorf("filtered field nested.foo cannot be set in a Blueprint file"),
-				Pos: mkpos(27, 4, 8),
+				Pos: mkpos(30, 4, 9),
 			},
 		},
 	},
 
 	// Anonymous struct
-	{`
-		m {
-			name: "abc",
-			nested: {
-				name: "def",
-			},
-		}
+	{
+		input: `
+			m {
+				name: "abc",
+				nested: {
+					name: "def",
+				},
+			}
 		`,
-		[]interface{}{
+		output: []interface{}{
 			struct {
 				EmbeddedStruct
 				Nested struct {
@@ -277,19 +280,19 @@ var validUnpackTestCases = []struct {
 				},
 			},
 		},
-		nil,
 	},
 
 	// Anonymous interface
-	{`
-		m {
-			name: "abc",
-			nested: {
-				name: "def",
-			},
-		}
+	{
+		input: `
+			m {
+				name: "abc",
+				nested: {
+					name: "def",
+				},
+			}
 		`,
-		[]interface{}{
+		output: []interface{}{
 			struct {
 				EmbeddedInterface
 				Nested struct {
@@ -308,19 +311,19 @@ var validUnpackTestCases = []struct {
 				},
 			},
 		},
-		nil,
 	},
 
 	// Anonymous struct with name collision
-	{`
-		m {
-			name: "abc",
-			nested: {
-				name: "def",
-			},
-		}
+	{
+		input: `
+			m {
+				name: "abc",
+				nested: {
+					name: "def",
+				},
+			}
 		`,
-		[]interface{}{
+		output: []interface{}{
 			struct {
 				Name string
 				EmbeddedStruct
@@ -344,19 +347,19 @@ var validUnpackTestCases = []struct {
 				},
 			},
 		},
-		nil,
 	},
 
 	// Anonymous interface with name collision
-	{`
-		m {
-			name: "abc",
-			nested: {
-				name: "def",
-			},
-		}
+	{
+		input: `
+			m {
+				name: "abc",
+				nested: {
+					name: "def",
+				},
+			}
 		`,
-		[]interface{}{
+		output: []interface{}{
 			struct {
 				Name string
 				EmbeddedInterface
@@ -380,21 +383,21 @@ var validUnpackTestCases = []struct {
 				},
 			},
 		},
-		nil,
 	},
 
 	// Variables
-	{`
-		list = ["abc"]
-		string = "def"
-		list_with_variable = [string]
-		m {
-			name: string,
-			list: list,
-			list2: list_with_variable,
-		}
+	{
+		input: `
+			list = ["abc"]
+			string = "def"
+			list_with_variable = [string]
+			m {
+				name: string,
+				list: list,
+				list2: list_with_variable,
+			}
 		`,
-		[]interface{}{
+		output: []interface{}{
 			struct {
 				Name  string
 				List  []string
@@ -405,18 +408,18 @@ var validUnpackTestCases = []struct {
 				List2: []string{"def"},
 			},
 		},
-		nil,
 	},
 
 	// Multiple property structs
-	{`
-		m {
-			nested: {
-				name: "abc",
+	{
+		input: `
+			m {
+				nested: {
+					name: "abc",
+				}
 			}
-		}
 		`,
-		[]interface{}{
+		output: []interface{}{
 			struct {
 				Nested struct {
 					Name string
@@ -438,7 +441,62 @@ var validUnpackTestCases = []struct {
 			struct {
 			}{},
 		},
-		nil,
+	},
+
+	// Nil pointer to struct
+	{
+		input: `
+			m {
+				nested: {
+					name: "abc",
+				}
+			}
+		`,
+		output: []interface{}{
+			struct {
+				Nested *struct {
+					Name string
+				}
+			}{
+				Nested: &struct{ Name string }{
+					Name: "abc",
+				},
+			},
+		},
+		empty: []interface{}{
+			&struct {
+				Nested *struct {
+					Name string
+				}
+			}{},
+		},
+	},
+
+	// Interface containing nil pointer to struct
+	{
+		input: `
+			m {
+				nested: {
+					name: "abc",
+				}
+			}
+		`,
+		output: []interface{}{
+			struct {
+				Nested interface{}
+			}{
+				Nested: &EmbeddedStruct{
+					Name: "abc",
+				},
+			},
+		},
+		empty: []interface{}{
+			&struct {
+				Nested interface{}
+			}{
+				Nested: (*EmbeddedStruct)(nil),
+			},
+		},
 	},
 }
 
@@ -464,9 +522,13 @@ func TestUnpackProperties(t *testing.T) {
 				continue
 			}
 
-			output := []interface{}{}
-			for _, p := range testCase.output {
-				output = append(output, proptools.CloneEmptyProperties(reflect.ValueOf(p)).Interface())
+			var output []interface{}
+			if len(testCase.empty) > 0 {
+				output = testCase.empty
+			} else {
+				for _, p := range testCase.output {
+					output = append(output, proptools.CloneEmptyProperties(reflect.ValueOf(p)).Interface())
+				}
 			}
 			_, errs = unpackProperties(module.Properties, output...)
 			if len(errs) != 0 && len(testCase.errs) == 0 {