1// Copyright 2019 Google Inc. All rights reserved.
2//
3// Licensed under the Apache License, Version 2.0 (the "License");
4// you may not use this file except in compliance with the License.
5// You may obtain a copy of the License at
6//
7//     http://www.apache.org/licenses/LICENSE-2.0
8//
9// Unless required by applicable law or agreed to in writing, software
10// distributed under the License is distributed on an "AS IS" BASIS,
11// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12// See the License for the specific language governing permissions and
13// limitations under the License.
14
15package android
16
17import (
18	"fmt"
19	"reflect"
20
21	"github.com/google/blueprint/proptools"
22)
23
24// This file implements support for automatically adding dependencies on any module referenced
25// with the ":module" module reference syntax in a property that is annotated with `android:"path"`.
26// The dependency is used by android.PathForModuleSrc to convert the module reference into the path
27// to the output file of the referenced module.
28
29func registerPathDepsMutator(ctx RegisterMutatorsContext) {
30	ctx.BottomUp("pathdeps", pathDepsMutator).Parallel()
31}
32
33// The pathDepsMutator automatically adds dependencies on any module that is listed with the
34// ":module" module reference syntax in a property that is tagged with `android:"path"`.
35func pathDepsMutator(ctx BottomUpMutatorContext) {
36	props := ctx.Module().base().generalProperties
37	addPathDepsForProps(ctx, props)
38}
39
40func addPathDepsForProps(ctx BottomUpMutatorContext, props []interface{}) {
41	// Iterate through each property struct of the module extracting the contents of all properties
42	// tagged with `android:"path"`.
43	var pathProperties []string
44	for _, ps := range props {
45		pathProperties = append(pathProperties, pathPropertiesForPropertyStruct(ps)...)
46	}
47
48	// Remove duplicates to avoid multiple dependencies.
49	pathProperties = FirstUniqueStrings(pathProperties)
50
51	// Add dependencies to anything that is a module reference.
52	for _, s := range pathProperties {
53		if m, t := SrcIsModuleWithTag(s); m != "" {
54			ctx.AddDependency(ctx.Module(), sourceOrOutputDepTag(t), m)
55		}
56	}
57}
58
59// pathPropertiesForPropertyStruct uses the indexes of properties that are tagged with
60// android:"path" to extract all their values from a property struct, returning them as a single
61// slice of strings.
62func pathPropertiesForPropertyStruct(ps interface{}) []string {
63	v := reflect.ValueOf(ps)
64	if v.Kind() != reflect.Ptr || v.Elem().Kind() != reflect.Struct {
65		panic(fmt.Errorf("type %s is not a pointer to a struct", v.Type()))
66	}
67
68	// If the property struct is a nil pointer it can't have any paths set in it.
69	if v.IsNil() {
70		return nil
71	}
72
73	// v is now the reflect.Value for the concrete property struct.
74	v = v.Elem()
75
76	// Get or create the list of indexes of properties that are tagged with `android:"path"`.
77	pathPropertyIndexes := pathPropertyIndexesForPropertyStruct(ps)
78
79	var ret []string
80
81	for _, i := range pathPropertyIndexes {
82		var values []reflect.Value
83		fieldsByIndex(v, i, &values)
84		for _, sv := range values {
85			if !sv.IsValid() {
86				// Skip properties inside a nil pointer.
87				continue
88			}
89
90			// If the field is a non-nil pointer step into it.
91			if sv.Kind() == reflect.Ptr {
92				if sv.IsNil() {
93					continue
94				}
95				sv = sv.Elem()
96			}
97
98			// Collect paths from all strings and slices of strings.
99			switch sv.Kind() {
100			case reflect.String:
101				ret = append(ret, sv.String())
102			case reflect.Slice:
103				ret = append(ret, sv.Interface().([]string)...)
104			default:
105				panic(fmt.Errorf(`field %s in type %s has tag android:"path" but is not a string or slice of strings, it is a %s`,
106					v.Type().FieldByIndex(i).Name, v.Type(), sv.Type()))
107			}
108		}
109	}
110
111	return ret
112}
113
114// fieldsByIndex is similar to reflect.Value.FieldByIndex, but is more robust: it doesn't track
115// nil pointers and it returns multiple values when there's slice of struct.
116func fieldsByIndex(v reflect.Value, index []int, values *[]reflect.Value) {
117	// leaf case
118	if len(index) == 1 {
119		if isSliceOfStruct(v) {
120			for i := 0; i < v.Len(); i++ {
121				*values = append(*values, v.Index(i).Field(index[0]))
122			}
123		} else {
124			// Dereference it if it's a pointer.
125			if v.Kind() == reflect.Ptr {
126				if v.IsNil() {
127					return
128				}
129				v = v.Elem()
130			}
131			*values = append(*values, v.Field(index[0]))
132		}
133		return
134	}
135
136	// recursion
137	if v.Kind() == reflect.Ptr {
138		// don't track nil pointer
139		if v.IsNil() {
140			return
141		}
142		v = v.Elem()
143	} else if isSliceOfStruct(v) {
144		// do the recursion for all elements
145		for i := 0; i < v.Len(); i++ {
146			fieldsByIndex(v.Index(i).Field(index[0]), index[1:], values)
147		}
148		return
149	}
150	fieldsByIndex(v.Field(index[0]), index[1:], values)
151	return
152}
153
154func isSliceOfStruct(v reflect.Value) bool {
155	return v.Kind() == reflect.Slice && v.Type().Elem().Kind() == reflect.Struct
156}
157
158var pathPropertyIndexesCache OncePer
159
160// pathPropertyIndexesForPropertyStruct returns a list of all of the indexes of properties in
161// property struct type that are tagged with `android:"path"`.  Each index is a []int suitable for
162// passing to reflect.Value.FieldByIndex.  The value is cached in a global cache by type.
163func pathPropertyIndexesForPropertyStruct(ps interface{}) [][]int {
164	key := NewCustomOnceKey(reflect.TypeOf(ps))
165	return pathPropertyIndexesCache.Once(key, func() interface{} {
166		return proptools.PropertyIndexesWithTag(ps, "android", "path")
167	}).([][]int)
168}
169