test: simplify tests

builtin.go → builtins.go

@@ -1,7 +1,7 @@
 package musttag
 
-// builtin is a set of functions supported out of the box.
-var builtin = []Func{
+// builtins is a set of functions supported out of the box.
+var builtins = []Func{
 	// https://pkg.go.dev/encoding/json
 	{Name: "encoding/json.Marshal", Tag: "json", ArgPos: 0},
 	{Name: "encoding/json.MarshalIndent", Tag: "json", ArgPos: 0},

musttag.go

@@ -34,14 +34,14 @@ func New(funcs ...Func) *analysis.Analyzer {
 		Flags:    flags(&flagFuncs),
 		Requires: []*analysis.Analyzer{inspect.Analyzer},
 		Run: func(pass *analysis.Pass) (any, error) {
-			l := len(builtin) + len(funcs) + len(flagFuncs)
+			l := len(builtins) + len(funcs) + len(flagFuncs)
 			m := make(map[string]Func, l)
 			toMap := func(slice []Func) {
 				for _, fn := range slice {
 					m[fn.Name] = fn
 				}
 			}
-			toMap(builtin)
+			toMap(builtins)
 			toMap(funcs)
 			toMap(flagFuncs)
 			return run(pass, m)
@@ -84,9 +84,9 @@ var (
 	}
 
 	// HACK(junk1tm): mainModulePackages() does not return packages from `testdata`,
-	// because it is ignored by the `go list` command.
-	// For tests to pass we need add these packages manually.
-	testPackages []string
+	// because it is ignored by the go tool, and thus, by the `go list` command.
+	// For tests to pass we need to add the package with tests to the main module manually.
+	testPackage string
 )
 
 // run starts the analysis.
@@ -95,8 +95,8 @@ func run(pass *analysis.Pass, funcs map[string]Func) (any, error) {
 	if err != nil {
 		return nil, err
 	}
-	for _, pkg := range testPackages {
-		mainModule[pkg] = struct{}{}
+	if testPackage != "" {
+		mainModule[testPackage] = struct{}{}
 	}
 
 	// store previous reports to prevent reporting

musttag_test.go

@@ -18,17 +18,16 @@ func TestAnalyzer(t *testing.T) {
 	// So, to be able to run tests with external dependencies,
 	// we first need to write a GOPATH-like tree of stubs.
 	prepareTestFiles(t)
-
-	testPackages = []string{"tests", "examples"}
+	testPackage = "tests"
 
 	analyzer := New(
 		Func{Name: "example.com/custom.Marshal", Tag: "custom", ArgPos: 0},
 		Func{Name: "example.com/custom.Unmarshal", Tag: "custom", ArgPos: 1},
 	)
 
-	t.Run("examples", func(t *testing.T) {
+	t.Run("builtins", func(t *testing.T) {
 		testdata := analysistest.TestData()
-		analysistest.Run(t, testdata, analyzer, "examples")
+		analysistest.Run(t, testdata, analyzer, "builtins")
 	})
 
 	t.Run("tests", func(t *testing.T) {
@@ -104,7 +103,7 @@ func prepareTestFiles(t *testing.T) {
 		}
 	}
 	hardlink("tests", "tests.go")
-	hardlink("examples", "examples.go")
+	hardlink("builtins", "builtins.go")
 
 	for file, data := range stubs {
 		target := filepath.Join(testdata, "src", file)

testdata/builtins.go

@@ -0,0 +1,84 @@
+package tests
+
+import (
+	"encoding/json"
+	"encoding/xml"
+
+	// these packages are generated before the tests are run.
+	"example.com/custom"
+	"github.com/BurntSushi/toml"
+	"github.com/mitchellh/mapstructure"
+	"gopkg.in/yaml.v3"
+)
+
+// TODO(junk1tm): drop `reportOnce` and test each builtin function.
+
+func testJSON() {
+	var user struct { // want `exported fields should be annotated with the "json" tag`
+		Name  string
+		Email string `json:"email"`
+	}
+	json.Marshal(user)
+	json.MarshalIndent(user, "", "")
+	json.Unmarshal(nil, &user)
+	json.NewEncoder(nil).Encode(user)
+	json.NewDecoder(nil).Decode(&user)
+}
+
+func testXML() {
+	var user struct { // want `exported fields should be annotated with the "xml" tag`
+		Name  string
+		Email string `xml:"email"`
+	}
+	xml.Marshal(user)
+	xml.MarshalIndent(user, "", "")
+	xml.Unmarshal(nil, &user)
+	xml.NewEncoder(nil).Encode(user)
+	xml.NewDecoder(nil).Decode(&user)
+	xml.NewEncoder(nil).EncodeElement(user, xml.StartElement{})
+	xml.NewDecoder(nil).DecodeElement(&user, &xml.StartElement{})
+}
+
+func testYAML() {
+	var user struct { // want `exported fields should be annotated with the "yaml" tag`
+		Name  string
+		Email string `yaml:"email"`
+	}
+	yaml.Marshal(user)
+	yaml.Unmarshal(nil, &user)
+	yaml.NewEncoder(nil).Encode(user)
+	yaml.NewDecoder(nil).Decode(&user)
+}
+
+func testTOML() {
+	var user struct { // want `exported fields should be annotated with the "toml" tag`
+		Name  string
+		Email string `toml:"email"`
+	}
+	toml.Unmarshal(nil, &user)
+	toml.Decode("", &user)
+	toml.DecodeFS(nil, "", &user)
+	toml.DecodeFile("", &user)
+	toml.NewEncoder(nil).Encode(user)
+	toml.NewDecoder(nil).Decode(&user)
+}
+
+func testMapstructure() {
+	var user struct { // want `exported fields should be annotated with the "mapstructure" tag`
+		Name  string
+		Email string `mapstructure:"email"`
+	}
+	mapstructure.Decode(nil, &user)
+	mapstructure.DecodeMetadata(nil, &user, nil)
+	mapstructure.WeakDecode(nil, &user)
+	mapstructure.WeakDecodeMetadata(nil, &user, nil)
+}
+
+func testCustom() {
+	var user struct { // want `exported fields should be annotated with the "custom" tag`
+		Name  string
+		Email string `custom:"email"`
+	}
+	custom.Marshal(user)
+	custom.Unmarshal(nil, &user)
+}