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15c0b25d AP |
1 | package gocty |
2 | ||
3 | import ( | |
4 | "reflect" | |
5 | ||
6 | "github.com/zclconf/go-cty/cty" | |
7 | ) | |
8 | ||
9 | // ImpliedType takes an arbitrary Go value (as an interface{}) and attempts | |
10 | // to find a suitable cty.Type instance that could be used for a conversion | |
11 | // with ToCtyValue. | |
12 | // | |
13 | // This allows -- for simple situations at least -- types to be defined just | |
14 | // once in Go and the cty types derived from the Go types, but in the process | |
15 | // it makes some assumptions that may be undesirable so applications are | |
16 | // encouraged to build their cty types directly if exacting control is | |
17 | // required. | |
18 | // | |
19 | // Not all Go types can be represented as cty types, so an error may be | |
20 | // returned which is usually considered to be a bug in the calling program. | |
21 | // In particular, ImpliedType will never use capsule types in its returned | |
22 | // type, because it cannot know the capsule types supported by the calling | |
23 | // program. | |
24 | func ImpliedType(gv interface{}) (cty.Type, error) { | |
25 | rt := reflect.TypeOf(gv) | |
26 | var path cty.Path | |
27 | return impliedType(rt, path) | |
28 | } | |
29 | ||
30 | func impliedType(rt reflect.Type, path cty.Path) (cty.Type, error) { | |
31 | switch rt.Kind() { | |
32 | ||
33 | case reflect.Ptr: | |
34 | return impliedType(rt.Elem(), path) | |
35 | ||
36 | // Primitive types | |
37 | case reflect.Bool: | |
38 | return cty.Bool, nil | |
39 | case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64: | |
40 | return cty.Number, nil | |
41 | case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64: | |
42 | return cty.Number, nil | |
43 | case reflect.Float32, reflect.Float64: | |
44 | return cty.Number, nil | |
45 | case reflect.String: | |
46 | return cty.String, nil | |
47 | ||
48 | // Collection types | |
49 | case reflect.Slice: | |
50 | path := append(path, cty.IndexStep{Key: cty.UnknownVal(cty.Number)}) | |
51 | ety, err := impliedType(rt.Elem(), path) | |
52 | if err != nil { | |
53 | return cty.NilType, err | |
54 | } | |
55 | return cty.List(ety), nil | |
56 | case reflect.Map: | |
57 | if !stringType.AssignableTo(rt.Key()) { | |
58 | return cty.NilType, path.NewErrorf("no cty.Type for %s (must have string keys)", rt) | |
59 | } | |
60 | path := append(path, cty.IndexStep{Key: cty.UnknownVal(cty.String)}) | |
61 | ety, err := impliedType(rt.Elem(), path) | |
62 | if err != nil { | |
63 | return cty.NilType, err | |
64 | } | |
65 | return cty.Map(ety), nil | |
66 | ||
67 | // Structural types | |
68 | case reflect.Struct: | |
69 | return impliedStructType(rt, path) | |
70 | ||
71 | default: | |
72 | return cty.NilType, path.NewErrorf("no cty.Type for %s", rt) | |
73 | } | |
74 | } | |
75 | ||
76 | func impliedStructType(rt reflect.Type, path cty.Path) (cty.Type, error) { | |
77 | if valueType.AssignableTo(rt) { | |
78 | // Special case: cty.Value represents cty.DynamicPseudoType, for | |
79 | // type conformance checking. | |
80 | return cty.DynamicPseudoType, nil | |
81 | } | |
82 | ||
83 | fieldIdxs := structTagIndices(rt) | |
84 | if len(fieldIdxs) == 0 { | |
85 | return cty.NilType, path.NewErrorf("no cty.Type for %s (no cty field tags)", rt) | |
86 | } | |
87 | ||
88 | atys := make(map[string]cty.Type, len(fieldIdxs)) | |
89 | ||
90 | { | |
91 | // Temporary extension of path for attributes | |
92 | path := append(path, nil) | |
93 | ||
94 | for k, fi := range fieldIdxs { | |
95 | path[len(path)-1] = cty.GetAttrStep{Name: k} | |
96 | ||
97 | ft := rt.Field(fi).Type | |
98 | aty, err := impliedType(ft, path) | |
99 | if err != nil { | |
100 | return cty.NilType, err | |
101 | } | |
102 | ||
103 | atys[k] = aty | |
104 | } | |
105 | } | |
106 | ||
107 | return cty.Object(atys), nil | |
108 | } |