feat: support mapstructure

README.md

@@ -38,6 +38,7 @@ The rational from [Uber Style Guide][1]:
 * `encoding/xml` support
 * `gopkg.in/yaml.v3` support
 * `github.com/BurntSushi/toml` support
+* `github.com/mitchellh/mapstructure` support
 
 ## 📦 Install
 
@@ -59,7 +60,6 @@ go vet -vettool=$(which musttag) ./...
 
 ## 📅 Roadmap
 
-* Support `mapstructure`
 * Support custom tags via config
 
 [1]: https://github.com/uber-go/guide/blob/master/style.md#use-field-tags-in-marshaled-structs

go.mod

@@ -4,6 +4,7 @@ go 1.18
 
 require (
 	github.com/BurntSushi/toml v1.2.1
+	github.com/mitchellh/mapstructure v1.5.0
 	golang.org/x/tools v0.3.0
 	gopkg.in/yaml.v3 v3.0.1
 )

go.sum

@@ -1,5 +1,7 @@
 github.com/BurntSushi/toml v1.2.1 h1:9F2/+DoOYIOksmaJFPw1tGFy1eDnIJXg+UHjuD8lTak=
 github.com/BurntSushi/toml v1.2.1/go.mod h1:CxXYINrC8qIiEnFrOxCa7Jy5BFHlXnUU2pbicEuybxQ=
+github.com/mitchellh/mapstructure v1.5.0 h1:jeMsZIYE/09sWLaz43PL7Gy6RuMjD2eJVyuac5Z2hdY=
+github.com/mitchellh/mapstructure v1.5.0/go.mod h1:bFUtVrKA4DC2yAKiSyO/QUcy7e+RRV2QTWOzhPopBRo=
 golang.org/x/mod v0.7.0 h1:LapD9S96VoQRhi/GrNTqeBJFrUjs5UHCAtTlgwA5oZA=
 golang.org/x/mod v0.7.0/go.mod h1:iBbtSCu2XBx23ZKBPSOrRkjjQPZFPuis4dIYUhu/chs=
 golang.org/x/sync v0.1.0 h1:wsuoTGHzEhffawBOhz5CYhcrV4IdKZbEyZjBMuTp12o=

musttag.go

@@ -14,6 +14,7 @@ import (
 	// we need these dependencies for the tests in testdata to compile.
 	// `go mod tidy` will remove them from go.mod if we don't import them here.
 	_ "github.com/BurntSushi/toml"
+	_ "github.com/mitchellh/mapstructure"
 	_ "gopkg.in/yaml.v3"
 )
 
@@ -82,10 +83,11 @@ func run(pass *analysis.Pass) (any, error) {
 // look for and the expression that likely contains the struct to check.
 func tagAndExpr(pass *analysis.Pass, call *ast.CallExpr) (string, ast.Expr, bool) {
 	const (
-		jsonTag = "json"
-		xmlTag  = "xml"
-		yamlTag = "yaml"
-		tomlTag = "toml"
+		jsonTag         = "json"
+		xmlTag          = "xml"
+		yamlTag         = "yaml"
+		tomlTag         = "toml"
+		mapstructureTag = "mapstructure"
 	)
 
 	fn := typeutil.StaticCallee(pass.TypesInfo, call)
@@ -129,6 +131,12 @@ func tagAndExpr(pass *analysis.Pass, call *ast.CallExpr) (string, ast.Expr, bool
 	case "github.com/BurntSushi/toml.DecodeFS":
 		return tomlTag, call.Args[2], true
 
+	case "github.com/mitchellh/mapstructure.Decode",
+		"github.com/mitchellh/mapstructure.DecodeMetadata",
+		"github.com/mitchellh/mapstructure.WeakDecode",
+		"github.com/mitchellh/mapstructure.WeakDecodeMetadata":
+		return mapstructureTag, call.Args[1], true
+
 	default:
 		return "", nil, false
 	}

testdata/src/examples/examples.go

@@ -5,6 +5,7 @@ import (
 	"encoding/xml"
 
 	"github.com/BurntSushi/toml"
+	"github.com/mitchellh/mapstructure"
 	"gopkg.in/yaml.v3"
 )
 
@@ -45,3 +46,12 @@ func exampleTOML() {
 	toml.Decode("", &user)
 	toml.Unmarshal(nil, &user)
 }
+
+func exampleMS() {
+	var user struct { // want `\Qexported fields should be annotated with the "mapstructure" tag`
+		Name  string
+		Email string `mapstructure:"email"`
+	}
+	mapstructure.Decode(nil, &user)
+	mapstructure.WeakDecode(nil, &user)
+}

testdata/src/github.com/mitchellh/mapstructure/mapstructure.go

@@ -0,0 +1,12 @@
+// Package mapstructure provides stubs for github.com/mitchellh/mapstructure.
+package mapstructure
+
+// mapstructure.NewDecoder wants the struct pointer to be passed via
+// mapstructure.DecoderConfig, that's why we do not support it for now.
+
+type Metadata struct{}
+
+func Decode(_, _ any) error                          { return nil }
+func DecodeMetadata(_, _ any, _ *Metadata) error     { return nil }
+func WeakDecode(_, _ any) error                      { return nil }
+func WeakDecodeMetadata(_, _ any, _ *Metadata) error { return nil }

testdata/src/tests/tests.go

@@ -5,6 +5,7 @@ import (
 	"encoding/xml"
 
 	"github.com/BurntSushi/toml"
+	"github.com/mitchellh/mapstructure"
 	"gopkg.in/yaml.v3"
 )
 
@@ -36,7 +37,12 @@ func namedType() {
 		`\Qtoml.DecodeFS`
 		`\Qtoml.DecodeFile`
 		`\Qtoml.Encoder.Encode`
-		`\Qtoml.Decoder.Decode` */
+		`\Qtoml.Decoder.Decode`
+
+		`\Qmapstructure.Decode`
+		`\Qmapstructure.DecodeMetadata`
+		`\Qmapstructure.WeakDecode`
+		`\Qmapstructure.WeakDecodeMetadata` */
 		NoTag int
 	}
 	var x X
@@ -66,6 +72,11 @@ func namedType() {
 	toml.DecodeFile("", &x)
 	toml.NewEncoder(nil).Encode(X{})
 	toml.NewDecoder(nil).Decode(&X{})
+
+	mapstructure.Decode(nil, &x)
+	mapstructure.DecodeMetadata(nil, &x, nil)
+	mapstructure.WeakDecode(nil, &X{})
+	mapstructure.WeakDecodeMetadata(nil, &X{}, nil)
 }
 
 func nestedNamedType() {
@@ -94,11 +105,16 @@ func nestedNamedType() {
 		`\Qtoml.DecodeFS`
 		`\Qtoml.DecodeFile`
 		`\Qtoml.Encoder.Encode`
-		`\Qtoml.Decoder.Decode` */
+		`\Qtoml.Decoder.Decode`
+
+		`\Qmapstructure.Decode`
+		`\Qmapstructure.DecodeMetadata`
+		`\Qmapstructure.WeakDecode`
+		`\Qmapstructure.WeakDecodeMetadata` */
 		NoTag int
 	}
 	type X struct {
-		Y Y `json:"y" xml:"y" yaml:"y" toml:"y"`
+		Y Y `json:"y" xml:"y" yaml:"y" toml:"y" mapstructure:"y"`
 	}
 	var x X
 
@@ -127,6 +143,11 @@ func nestedNamedType() {
 	toml.DecodeFile("", &x)
 	toml.NewEncoder(nil).Encode(X{})
 	toml.NewDecoder(nil).Decode(&X{})
+
+	mapstructure.Decode(nil, &x)
+	mapstructure.DecodeMetadata(nil, &x, nil)
+	mapstructure.WeakDecode(nil, &X{})
+	mapstructure.WeakDecodeMetadata(nil, &X{}, nil)
 }
 
 func anonymousType() {
@@ -145,7 +166,10 @@ func anonymousType() {
 		`\Qtoml.Unmarshal`
 		`\Qtoml.Decode`
 		`\Qtoml.DecodeFS`
-		`\Qtoml.DecodeFile` */
+		`\Qtoml.DecodeFile`
+
+		`\Qmapstructure.Decode`
+		`\Qmapstructure.DecodeMetadata` */
 		NoTag int
 	}
 
@@ -174,6 +198,11 @@ func anonymousType() {
 	toml.DecodeFile("", &x)
 	toml.NewEncoder(nil).Encode(struct{ NoTag int }{})  // want `\Qtoml.Encoder.Encode`
 	toml.NewDecoder(nil).Decode(&struct{ NoTag int }{}) // want `\Qtoml.Decoder.Decode`
+
+	mapstructure.Decode(nil, &x)
+	mapstructure.DecodeMetadata(nil, &x, nil)
+	mapstructure.WeakDecode(nil, &struct{ NoTag int }{})              // want `\Qmapstructure.WeakDecode`
+	mapstructure.WeakDecodeMetadata(nil, &struct{ NoTag int }{}, nil) // want `\Qmapstructure.WeakDecodeMetadata`
 }
 
 func nestedAnonymousType() {
@@ -192,8 +221,11 @@ func nestedAnonymousType() {
 		`\Qtoml.Unmarshal`
 		`\Qtoml.Decode`
 		`\Qtoml.DecodeFS`
-		`\Qtoml.DecodeFile` */
-		Y *struct{ NoTag int } `json:"y" xml:"y" yaml:"y" toml:"y"`
+		`\Qtoml.DecodeFile`
+
+		`\Qmapstructure.Decode`
+		`\Qmapstructure.DecodeMetadata` */
+		Y *struct{ NoTag int } `json:"y" xml:"y" yaml:"y" toml:"y" mapstructure:"y"`
 	}
 
 	json.Marshal(x)
@@ -221,14 +253,19 @@ func nestedAnonymousType() {
 	toml.DecodeFile("", &x)
 	toml.NewEncoder(nil).Encode(struct{ Y struct{ NoTag int } }{})  // want `\Qtoml.Encoder.Encode`
 	toml.NewDecoder(nil).Decode(&struct{ Y struct{ NoTag int } }{}) // want `\Qtoml.Decoder.Decode`
+
+	mapstructure.Decode(nil, &x)
+	mapstructure.DecodeMetadata(nil, &x, nil)
+	mapstructure.WeakDecode(nil, &struct{ Y struct{ NoTag int } }{})              // want `\Qmapstructure.WeakDecode`
+	mapstructure.WeakDecodeMetadata(nil, &struct{ Y struct{ NoTag int } }{}, nil) // want `\Qmapstructure.WeakDecodeMetadata`
 }
 
 // all good, nothing to report.
 func typeWithAllTags() {
 	var x struct {
-		Y       int      `json:"y" xml:"y" yaml:"y" toml:"y"`
-		Z       int      `json:"z" xml:"z" yaml:"z" toml:"z"`
-		Nested  struct{} `json:"nested" xml:"nested" yaml:"nested" toml:"nested"`
+		Y       int      `json:"y" xml:"y" yaml:"y" toml:"y" mapstructure:"y"`
+		Z       int      `json:"z" xml:"z" yaml:"z" toml:"z" mapstructure:"z"`
+		Nested  struct{} `json:"nested" xml:"nested" yaml:"nested" toml:"nested" mapstructure:"nested"`
 		private int
 	}
 
@@ -257,6 +294,11 @@ func typeWithAllTags() {
 	toml.DecodeFile("", &x)
 	toml.NewEncoder(nil).Encode(x)
 	toml.NewDecoder(nil).Decode(&x)
+
+	mapstructure.Decode(nil, &x)
+	mapstructure.DecodeMetadata(nil, &x, nil)
+	mapstructure.WeakDecode(nil, &x)
+	mapstructure.WeakDecodeMetadata(nil, &x, nil)
 }
 
 // non-static calls should be ignored.
@@ -276,6 +318,9 @@ func nonStaticCalls() {
 
 	unmarshalTOML := toml.Unmarshal
 	unmarshalTOML(nil, &x)
+
+	decodeMS := mapstructure.Decode
+	decodeMS(nil, &x)
 }
 
 // non-struct argument calls should be ignored.
@@ -305,4 +350,9 @@ func nonStructArgument() {
 	toml.DecodeFile("", &[]int{})
 	toml.NewEncoder(nil).Encode(map[int]int{})
 	toml.NewDecoder(nil).Decode(&map[int]int{})
+
+	mapstructure.Decode(nil, &[]int{})
+	mapstructure.DecodeMetadata(nil, &[]int{}, nil)
+	mapstructure.WeakDecode(nil, &map[int]int{})
+	mapstructure.WeakDecodeMetadata(nil, &map[int]int{}, nil)
 }