[checkapi] support generics and map keys (#1117)

Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>

Author: atoulme

.chloggen/support_generics_in_fields.yaml

@@ -0,0 +1,16 @@
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: bug_fix
+
+# The name of the component, or a single word describing the area of concern, (e.g. crosslink)
+component: checkapi
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Support detecting usage of a Struct as part of config when used as a generic type of a map key
+
+# One or more tracking issues related to the change
+issues: [1116]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext:

checkapi/internal/ast.go

@@ -121,6 +121,37 @@ func Read(folder string, ignoredFunctions []string, excludedFiles []string) (API
 	return *result, nil
 }
 
+func interpretFieldType(f *ast.Field, expr ast.Expr) []APIstructField {
+	var fieldNames []APIstructField
+	fieldType := expr
+	switch t := fieldType.(type) {
+	case *ast.StarExpr:
+		fieldType = t.X
+	case *ast.ArrayType:
+		fieldType = t.Elt
+		if tt, ok := fieldType.(*ast.StarExpr); ok {
+			fieldType = tt.X
+		}
+	case *ast.MapType:
+		fieldType = t.Value
+		if tt, ok := fieldType.(*ast.StarExpr); ok {
+			fieldType = tt.X
+		}
+		fieldNames = interpretFieldType(f, t.Key)
+	case *ast.Ident:
+		// nothing to do
+	case *ast.ChanType:
+		fieldType = t.Value
+	case *ast.StructType:
+		// nothing to do
+	case *ast.IndexExpr:
+		fieldType = t.X
+		fieldNames = interpretFieldType(f, t.Index)
+	}
+	fieldNames = append(fieldNames, APIstructField{Name: f.Names[0].Name, Type: ExprToString(fieldType)})
+	return fieldNames
+}
+
 func readFile(ignoredFunctions []string, f *ast.File, result *API) {
 	for _, d := range f.Decls {
 		if str, isStr := d.(*ast.GenDecl); isStr {
@@ -139,22 +170,7 @@ func readFile(ignoredFunctions []string, f *ast.File, result *API) {
 							fieldNames = make([]APIstructField, 0, len(structType.Fields.List))
 							for _, f := range structType.Fields.List {
 								if len(f.Names) > 0 {
-									fieldType := f.Names[0].Obj.Decl.(*ast.Field).Type
-									switch t := fieldType.(type) {
-									case *ast.StarExpr:
-										fieldType = t.X
-									case *ast.ArrayType:
-										fieldType = t.Elt
-										if tt, ok := fieldType.(*ast.StarExpr); ok {
-											fieldType = tt.X
-										}
-									case *ast.MapType:
-										fieldType = t.Value
-										if tt, ok := fieldType.(*ast.StarExpr); ok {
-											fieldType = tt.X
-										}
-									}
-									fieldNames = append(fieldNames, APIstructField{Name: f.Names[0].Name, Type: ExprToString(fieldType)})
+									fieldNames = append(fieldNames, interpretFieldType(f, f.Names[0].Obj.Decl.(*ast.Field).Type)...)
 								} else {
 									// Embedded struct
 									fieldType := f.Type

checkapi/internal/config/receiver/configreceiver/code_test.go

@@ -30,8 +30,16 @@ type Config struct {
 	Embedded
 	// Embedded struct pointer
 	*EmbeddedPtr
+	// Generic type
+	Holder GenericHolder[GenericType]
+	// Map holding types
+	MapOfStructs map[Key]Value
 }
 
+type Key struct{}
+
+type Value struct{}
+
 type PtrStruct struct {
 	Field string
 }
@@ -53,3 +61,11 @@ type Embedded struct {
 type EmbeddedPtr struct {
 	Foo string
 }
+
+type GenericHolder[T any] struct {
+	Value T
+}
+
+type GenericType struct {
+	Foo string
+}