bpf2go: import package structs when all structs are typedefs

When deciding whether to import package structs, the logic only considered
typical struct declarations. Typedefs also need to be taken into account.

Signed-off-by: Ron Federman <ron@odigos.io>
Co-authored-by: Timo Beckers <timo@isovalent.com>

Author: RonFed

cmd/bpf2go/gen/output.go

@@ -169,7 +169,7 @@ func Generate(args GenerateArgs) error {
 		if err != nil {
 			return fmt.Errorf("generating %s: %w", name, err)
 		}
-		_, ok := typ.(*btf.Struct)
+		_, ok := btf.As[*btf.Struct](typ)
 		needsStructsPkg = needsStructsPkg || ok
 		typeDecls = append(typeDecls, decl)
 	}

cmd/bpf2go/gen/output_test.go

@@ -118,3 +118,56 @@ func TestObjects(t *testing.T) {
 	qt.Assert(t, qt.StringContains(str, "Var1 *ebpf.Variable `ebpf:\"var_1\"`"))
 	qt.Assert(t, qt.StringContains(str, "ProgFoo1 *ebpf.Program `ebpf:\"prog_foo_1\"`"))
 }
+
+func TestGenerateStructTypes(t *testing.T) {
+	ts := &btf.Struct{
+		Name: "test_struct",
+		Size: 8,
+		Members: []btf.Member{
+			{
+				Name:   "field1",
+				Type:   &btf.Int{Size: 8, Encoding: btf.Unsigned},
+				Offset: 0,
+			},
+		},
+	}
+	td := &btf.Typedef{
+		Name: "test_typedef",
+		Type: ts,
+	}
+
+	tests := []struct {
+		name     string
+		types    []btf.Type
+		expected string
+	}{
+		{
+			name:     "simple struct",
+			types:    []btf.Type{ts},
+			expected: "type stemTestStruct struct {\n\t_      structs.HostLayout\n\tField1 uint64\n}",
+		},
+		{
+			name:     "typedef struct",
+			types:    []btf.Type{td},
+			expected: "type stemTestTypedef struct {\n\t_      structs.HostLayout\n\tField1 uint64\n}",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			var buf bytes.Buffer
+			err := Generate(GenerateArgs{
+				Package:     "test",
+				Stem:        "stem",
+				Types:       tt.types,
+				Output:      &buf,
+				Constraints: nil,
+			})
+			qt.Assert(t, qt.IsNil(err))
+
+			str := buf.String()
+			qt.Assert(t, qt.StringContains(str, tt.expected))
+			qt.Assert(t, qt.StringContains(str, "\"structs\""))
+		})
+	}
+}