Track pointer initialization for zero values (#73)

This fixes a bug where a pointer was initialized, but to the zero value. Like a *bool initialized to &false. Previously this would be considered "unset" because false is the zero value for a boolean. Now envconfig considers whether the pointer was initialized first, before checking whether the value is zero.

Author: sethvargo

envconfig.go

@@ -304,6 +304,7 @@ func processWith(ctx context.Context, i interface{}, l Lookuper, parentNoInit bo
 		}
 
 		// Initialize pointer structs.
+		pointerWasSet := false
 		for ef.Kind() == reflect.Ptr {
 			if ef.IsNil() {
 				if ef.Type().Elem().Kind() != reflect.Struct {
@@ -316,6 +317,7 @@ func processWith(ctx context.Context, i interface{}, l Lookuper, parentNoInit bo
 				// Use an empty struct of the type so we can traverse.
 				ef = reflect.New(ef.Type().Elem()).Elem()
 			} else {
+				pointerWasSet = true
 				ef = ef.Elem()
 			}
 		}
@@ -370,7 +372,7 @@ func processWith(ctx context.Context, i interface{}, l Lookuper, parentNoInit bo
 
 		// The field already has a non-zero value and overwrite is false, do not
 		// overwrite.
-		if !ef.IsZero() && !opts.Overwrite {
+		if (pointerWasSet || !ef.IsZero()) && !opts.Overwrite {
 			continue
 		}
 
@@ -382,7 +384,7 @@ func processWith(ctx context.Context, i interface{}, l Lookuper, parentNoInit bo
 		// If the field already has a non-zero value and there was no value directly
 		// specified, do not overwrite the existing field. We only want to overwrite
 		// when the envvar was provided directly.
-		if !ef.IsZero() && !found {
+		if (pointerWasSet || !ef.IsZero()) && !found {
 			continue
 		}
 

envconfig_test.go

@@ -214,6 +214,18 @@ type Button struct {
 
 type Base64ByteSlice []Base64Bytes
 
+func boolPtr(b bool) *bool {
+	return &b
+}
+
+func stringPtr(s string) *string {
+	return &s
+}
+
+func intPtr(i int) *int {
+	return &i
+}
+
 func TestProcessWith(t *testing.T) {
 	t.Parallel()
 
@@ -1445,35 +1457,49 @@ func TestProcessWith(t *testing.T) {
 
 		// Pointer pointers
 		{
-			name: "string_pointer",
+			name: "pointer_string",
 			input: &struct {
 				Field *string `env:"FIELD"`
 			}{},
 			exp: &struct {
 				Field *string `env:"FIELD"`
 			}{
-				Field: func() *string { s := "foo"; return &s }(),
+				Field: stringPtr("foo"),
 			},
 			lookuper: MapLookuper(map[string]string{
 				"FIELD": "foo",
 			}),
 		},
 		{
-			name: "string_pointer_pointer",
+			name: "pointer_pointer_string",
 			input: &struct {
 				Field **string `env:"FIELD"`
 			}{},
 			exp: &struct {
 				Field **string `env:"FIELD"`
 			}{
-				Field: func() **string { s := "foo"; ptr := &s; return &ptr }(),
+				Field: func() **string { ptr := stringPtr("foo"); return &ptr }(),
 			},
 			lookuper: MapLookuper(map[string]string{
 				"FIELD": "foo",
 			}),
 		},
 		{
-			name: "map_pointer",
+			name: "pointer_int",
+			input: &struct {
+				Field *int `env:"FIELD"`
+			}{},
+			exp: &struct {
+				Field *int `env:"FIELD"`
+			}{
+				Field: intPtr(5),
+			},
+			lookuper: MapLookuper(map[string]string{
+				"FIELD": "5",
+			}),
+		},
+		{
+			name: "pointer_map",
 			input: &struct {
 				Field *map[string]string `env:"FIELD"`
 			}{},
@@ -1490,7 +1516,7 @@ func TestProcessWith(t *testing.T) {
 			}),
 		},
 		{
-			name: "slice_pointer",
+			name: "pointer_slice",
 			input: &struct {
 				Field *[]string `env:"FIELD"`
 			}{},
@@ -1507,7 +1533,21 @@ func TestProcessWith(t *testing.T) {
 			}),
 		},
 		{
-			name: "bool_pointer",
+			name: "pointer_bool",
+			input: &struct {
+				Field *bool `env:"FIELD"`
+			}{},
+			exp: &struct {
+				Field *bool `env:"FIELD"`
+			}{
+				Field: boolPtr(true),
+			},
+			lookuper: MapLookuper(map[string]string{
+				"FIELD": "true",
+			}),
+		},
+		{
+			name: "pointer_bool_noinit",
 			input: &struct {
 				Field *bool `env:"FIELD,noinit"`
 			}{},
@@ -1518,6 +1558,118 @@ func TestProcessWith(t *testing.T) {
 			},
 			lookuper: MapLookuper(nil),
 		},
+		{
+			name: "pointer_bool_default_field_set_env_unset",
+			input: &struct {
+				Field *bool `env:"FIELD,default=true"`
+			}{
+				Field: boolPtr(false),
+			},
+			exp: &struct {
+				Field *bool `env:"FIELD,default=true"`
+			}{
+				Field: boolPtr(false),
+			},
+			lookuper: MapLookuper(nil),
+		},
+		{
+			name: "pointer_bool_default_field_set_env_set",
+			input: &struct {
+				Field *bool `env:"FIELD,default=true"`
+			}{
+				Field: boolPtr(false),
+			},
+			exp: &struct {
+				Field *bool `env:"FIELD,default=true"`
+			}{
+				Field: boolPtr(false),
+			},
+			lookuper: MapLookuper(map[string]string{
+				"FIELD": "true",
+			}),
+		},
+		{
+			name: "pointer_bool_default_field_unset_env_set",
+			input: &struct {
+				Field *bool `env:"FIELD,default=true"`
+			}{},
+			exp: &struct {
+				Field *bool `env:"FIELD,default=true"`
+			}{
+				Field: boolPtr(false),
+			},
+			lookuper: MapLookuper(map[string]string{
+				"FIELD": "false",
+			}),
+		},
+		{
+			name: "pointer_bool_default_field_unset_env_unset",
+			input: &struct {
+				Field *bool `env:"FIELD,default=true"`
+			}{},
+			exp: &struct {
+				Field *bool `env:"FIELD,default=true"`
+			}{
+				Field: boolPtr(true),
+			},
+			lookuper: MapLookuper(nil),
+		},
+		{
+			name: "pointer_bool_default_overwrite_field_set_env_unset",
+			input: &struct {
+				Field *bool `env:"FIELD,overwrite,default=true"`
+			}{
+				Field: boolPtr(false),
+			},
+			exp: &struct {
+				Field *bool `env:"FIELD,overwrite,default=true"`
+			}{
+				Field: boolPtr(false),
+			},
+			lookuper: MapLookuper(nil),
+		},
+		{
+			name: "pointer_bool_default_overwrite_field_set_env_set",
+			input: &struct {
+				Field *bool `env:"FIELD,overwrite,default=true"`
+			}{
+				Field: boolPtr(false),
+			},
+			exp: &struct {
+				Field *bool `env:"FIELD,overwrite,default=true"`
+			}{
+				Field: boolPtr(true),
+			},
+			lookuper: MapLookuper(map[string]string{
+				"FIELD": "true",
+			}),
+		},
+		{
+			name: "pointer_bool_default_overwrite_field_unset_env_set",
+			input: &struct {
+				Field *bool `env:"FIELD,overwrite,default=true"`
+			}{},
+			exp: &struct {
+				Field *bool `env:"FIELD,overwrite,default=true"`
+			}{
+				Field: boolPtr(false),
+			},
+			lookuper: MapLookuper(map[string]string{
+				"FIELD": "false",
+			}),
+		},
+		{
+			name: "pointer_bool_default_overwrite_field_unset_env_unset",
+			input: &struct {
+				Field *bool `env:"FIELD,overwrite,default=true"`
+			}{},
+			exp: &struct {
+				Field *bool `env:"FIELD,overwrite,default=true"`
+			}{
+				Field: boolPtr(true),
+			},
+			lookuper: MapLookuper(nil),
+		},
 
 		// Marshallers
 		{