internal/postgres: populate modules.incompatible field

This change modifies the InsertModule function to insert modules with an
Incompatible field for the new Incompatible column in the modules table.

A test is added to check the latest version of inserted modules.

Updates golang/go#37714

Change-Id: I7ef04b8709f9499d747d9795531cbc83b5de25ad
Reviewed-on: https://go-review.googlesource.com/c/pkgsite/+/247757
Reviewed-by: Julie Qiu <julie@golang.org>

internal/postgres/insert_module.go

@@ -183,8 +183,9 @@ func insertModule(ctx context.Context, db *database.DB, m *internal.Module) (_ i
 			series_path,
 			source_info,
 			redistributable,
-			has_go_mod)
-		VALUES($1,$2,$3,$4,$5,$6,$7,$8,$9,$10, $11)
+			has_go_mod,
+			incompatible)
+		VALUES($1,$2,$3,$4,$5,$6,$7,$8,$9,$10,$11,$12)
 		ON CONFLICT
 			(module_path, version)
 		DO UPDATE SET
@@ -204,6 +205,7 @@ func insertModule(ctx context.Context, db *database.DB, m *internal.Module) (_ i
 		sourceInfoJSON,
 		m.IsRedistributable,
 		m.HasGoMod,
+		isIncompatible(m.Version),
 	).Scan(&moduleID)
 	if err != nil {
 		return 0, err
@@ -557,13 +559,19 @@ func lock(ctx context.Context, tx *database.DB, modulePath string) (err error) {
 	return nil
 }
 
+// isIncompatible reports whether the build metadata of the version is
+// "+incompatible", https://semver.org clause 10.
+func isIncompatible(version string) bool {
+	return strings.HasSuffix(version, "+incompatible")
+}
+
 // isLatestVersion reports whether version is the latest version of the module.
 func isLatestVersion(ctx context.Context, db *database.DB, modulePath, version string) (_ bool, err error) {
 	defer derrors.Wrap(&err, "isLatestVersion(ctx, tx, %q)", modulePath)
 
 	row := db.QueryRow(ctx, `
 		SELECT version FROM modules WHERE module_path = $1
-		ORDER BY version_type = 'release' DESC, sort_version DESC
+		ORDER BY incompatible, version_type = 'release' DESC, sort_version DESC
 		LIMIT 1`,
 		modulePath)
 	var v string

internal/postgres/insert_module_test.go

@@ -343,6 +343,67 @@ func TestPostgres_ReadAndWriteModuleOtherColumns(t *testing.T) {
 	}
 }
 
+func TestLatestVersion(t *testing.T) {
+	// Verify that finding the latest version of a module prefers
+	// non-incompatible versions first.
+	defer ResetTestDB(testDB, t)
+	ctx := context.Background()
+
+	for _, mod := range []struct {
+		version      string
+		modulePath   string
+		Incompatible bool
+	}{
+		{
+			version:    "v1.5.2",
+			modulePath: sample.ModulePath,
+		},
+		{
+			version:    "v2.0.0+incompatible",
+			modulePath: sample.ModulePath,
+		},
+		{
+			version:    "v2.0.1",
+			modulePath: sample.ModulePath + "/v2",
+		},
+	} {
+		m := sample.DefaultModule()
+		m.Version = mod.version
+		m.ModulePath = mod.modulePath
+
+		if err := testDB.InsertModule(ctx, m); err != nil {
+			t.Fatal(err)
+		}
+	}
+
+	for _, tc := range []struct {
+		name        string
+		modulePath  string
+		wantVersion string
+	}{
+		{
+			name:        "test v1 version",
+			modulePath:  sample.ModulePath,
+			wantVersion: "v1.5.2",
+		},
+		{
+			name:        "test v2 version",
+			modulePath:  sample.ModulePath + "/v2",
+			wantVersion: "v2.0.1",
+		},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			isLatest, err := isLatestVersion(ctx, testDB.db, tc.modulePath, tc.wantVersion)
+			if err != nil {
+				t.Fatal(err)
+			}
+			if !isLatest {
+				t.Errorf("\n%+v is not the Latest version: %+v", tc.modulePath, tc.wantVersion)
+			}
+		})
+	}
+}
+
 func TestDeleteModule(t *testing.T) {
 	ctx, cancel := context.WithTimeout(context.Background(), testTimeout)
 	defer cancel()