[feature] Allow full BCP 47 in language inputs (#2067)

* Allow full BCP 47 in language inputs

Fixes #2066

* Fuse validation and normalization for languages

* Remove outdated comment line

* Move post language canonicalization test

9 files changed, 134 insertions, 72 deletions

diff --git a/internal/api/client/accounts/accountcreate.go b/internal/api/client/accounts/accountcreate.go
index c8247ecf2..473000f6d 100644
--- a/internal/api/client/accounts/accountcreate.go
+++ b/internal/api/client/accounts/accountcreate.go
@@ -87,7 +87,7 @@ func (m *Module) AccountCreatePOSTHandler(c *gin.Context) {
 		return
 	}
 
-	if err := validateCreateAccount(form); err != nil {
+	if err := validateNormalizeCreateAccount(form); err != nil {
 		apiutil.ErrorHandler(c, gtserror.NewErrorBadRequest(err, err.Error()), m.processor.InstanceGetV1)
 		return
 	}
@@ -110,9 +110,10 @@ func (m *Module) AccountCreatePOSTHandler(c *gin.Context) {
 	c.JSON(http.StatusOK, ti)
 }
 
-// validateCreateAccount checks through all the necessary prerequisites for creating a new account,
+// validateNormalizeCreateAccount checks through all the necessary prerequisites for creating a new account,
 // according to the provided account create request. If the account isn't eligible, an error will be returned.
-func validateCreateAccount(form *apimodel.AccountCreateRequest) error {
+// Side effect: normalizes the provided language tag for the user's locale.
+func validateNormalizeCreateAccount(form *apimodel.AccountCreateRequest) error {
 	if form == nil {
 		return errors.New("form was nil")
 	}
@@ -137,9 +138,11 @@ func validateCreateAccount(form *apimodel.AccountCreateRequest) error {
 		return errors.New("agreement to terms and conditions not given")
 	}
 
-	if err := validate.Language(form.Locale); err != nil {
+	locale, err := validate.Language(form.Locale)
+	if err != nil {
 		return err
 	}
+	form.Locale = locale
 
 	return validate.SignUpReason(form.Reason, config.GetAccountsReasonRequired())
 }
diff --git a/internal/api/client/statuses/statuscreate.go b/internal/api/client/statuses/statuscreate.go
index e4d8588c7..e8378f461 100644
--- a/internal/api/client/statuses/statuscreate.go
+++ b/internal/api/client/statuses/statuscreate.go
@@ -98,7 +98,7 @@ func (m *Module) StatusCreatePOSTHandler(c *gin.Context) {
 	// }
 	// form.Status += "\n\nsent from " + user + "'s iphone\n"
 
-	if err := validateCreateStatus(form); err != nil {
+	if err := validateNormalizeCreateStatus(form); err != nil {
 		apiutil.ErrorHandler(c, gtserror.NewErrorBadRequest(err, err.Error()), m.processor.InstanceGetV1)
 		return
 	}
@@ -112,7 +112,9 @@ func (m *Module) StatusCreatePOSTHandler(c *gin.Context) {
 	c.JSON(http.StatusOK, apiStatus)
 }
 
-func validateCreateStatus(form *apimodel.AdvancedStatusCreateForm) error {
+// validateNormalizeCreateStatus checks the form for disallowed combinations of attachments and overlength inputs.
+// Side effect: normalizes the post's language tag.
+func validateNormalizeCreateStatus(form *apimodel.AdvancedStatusCreateForm) error {
 	hasStatus := form.Status != ""
 	hasMedia := len(form.MediaIDs) != 0
 	hasPoll := form.Poll != nil
@@ -162,9 +164,11 @@ func validateCreateStatus(form *apimodel.AdvancedStatusCreateForm) error {
 	}
 
 	if form.Language != "" {
-		if err := validate.Language(form.Language); err != nil {
+		language, err := validate.Language(form.Language)
+		if err != nil {
 			return err
 		}
+		form.Language = language
 	}
 
 	return nil
diff --git a/internal/api/client/statuses/statuscreate_test.go b/internal/api/client/statuses/statuscreate_test.go
index 05f24c24c..d47a74bbc 100644
--- a/internal/api/client/statuses/statuscreate_test.go
+++ b/internal/api/client/statuses/statuscreate_test.go
@@ -391,6 +391,42 @@ func (suite *StatusCreateTestSuite) TestAttachNewMediaSuccess() {
 	suite.Equal(statusResponse.ID, gtsAttachment.StatusID)
 }
 
+// Post a new status with a language tag that is not in canonical format
+func (suite *StatusCreateTestSuite) TestPostNewStatusWithNoncanonicalLanguageTag() {
+	t := suite.testTokens["local_account_1"]
+	oauthToken := oauth.DBTokenToToken(t)
+
+	// setup
+	recorder := httptest.NewRecorder()
+	ctx, _ := testrig.CreateGinTestContext(recorder, nil)
+	ctx.Set(oauth.SessionAuthorizedApplication, suite.testApplications["application_1"])
+	ctx.Set(oauth.SessionAuthorizedToken, oauthToken)
+	ctx.Set(oauth.SessionAuthorizedUser, suite.testUsers["local_account_1"])
+	ctx.Set(oauth.SessionAuthorizedAccount, suite.testAccounts["local_account_1"])
+	ctx.Request = httptest.NewRequest(http.MethodPost, fmt.Sprintf("http://localhost:8080/%s", statuses.BasePath), nil) // the endpoint we're hitting
+	ctx.Request.Header.Set("accept", "application/json")
+	ctx.Request.Form = url.Values{
+		"status":   {"English? what's English? i speak American"},
+		"language": {"en-us"},
+	}
+	suite.statusModule.StatusCreatePOSTHandler(ctx)
+
+	suite.EqualValues(http.StatusOK, recorder.Code)
+
+	result := recorder.Result()
+	defer result.Body.Close()
+	b, err := ioutil.ReadAll(result.Body)
+	suite.NoError(err)
+
+	statusReply := &apimodel.Status{}
+	err = json.Unmarshal(b, statusReply)
+	suite.NoError(err)
+
+	suite.Equal("<p>English? what's English? i speak American</p>", statusReply.Content)
+	suite.NotNil(statusReply.Language)
+	suite.Equal("en-US", *statusReply.Language)
+}
+
 func TestStatusCreateTestSuite(t *testing.T) {
 	suite.Run(t, new(StatusCreateTestSuite))
 }
diff --git a/internal/processing/account/create.go b/internal/processing/account/create.go
index 1a172b865..32a59d1ef 100644
--- a/internal/processing/account/create.go
+++ b/internal/processing/account/create.go
@@ -34,8 +34,7 @@ import (
 // Create processes the given form for creating a new account,
 // returning an oauth token for that account if successful.
 //
-// Fields on the form should have already been validated by the
-// caller, before this function is called.
+// Precondition: the form's fields should have already been validated and normalized by the caller.
 func (p *Processor) Create(
 	ctx context.Context,
 	appToken oauth2.TokenInfo,
diff --git a/internal/processing/account/update.go b/internal/processing/account/update.go
index 01c62d7e3..f75b3c8d9 100644
--- a/internal/processing/account/update.go
+++ b/internal/processing/account/update.go
@@ -222,10 +222,11 @@ func (p *Processor) Update(ctx context.Context, account *gtsmodel.Account, form
 
 	if form.Source != nil {
 		if form.Source.Language != nil {
-			if err := validate.Language(*form.Source.Language); err != nil {
+			language, err := validate.Language(*form.Source.Language)
+			if err != nil {
 				return nil, gtserror.NewErrorBadRequest(err)
 			}
-			account.Language = *form.Source.Language
+			account.Language = language
 		}
 
 		if form.Source.Sensitive != nil {
diff --git a/internal/processing/status/create.go b/internal/processing/status/create.go
index 2d9c3a196..36842ee07 100644
--- a/internal/processing/status/create.go
+++ b/internal/processing/status/create.go
@@ -37,6 +37,8 @@ import (
 )
 
 // Create processes the given form to create a new status, returning the api model representation of that status if it's OK.
+//
+// Precondition: the form's fields should have already been validated and normalized by the caller.
 func (p *Processor) Create(ctx context.Context, account *gtsmodel.Account, application *gtsmodel.Application, form *apimodel.AdvancedStatusCreateForm) (*apimodel.Status, gtserror.WithCode) {
 	accountURIs := uris.GenerateURIsForAccount(account.Username)
 	thisStatusID := id.NewULID()
@@ -55,7 +57,6 @@ func (p *Processor) Create(ctx context.Context, account *gtsmodel.Account, appli
 		ContentWarning:           text.SanitizePlaintext(form.SpoilerText),
 		ActivityStreamsType:      ap.ObjectNote,
 		Sensitive:                &sensitive,
-		Language:                 form.Language,
 		CreatedWithApplicationID: application.ID,
 		Text:                     form.Status,
 	}
diff --git a/internal/processing/status/create_test.go b/internal/processing/status/create_test.go
index 2a797516d..2c86e5a29 100644
--- a/internal/processing/status/create_test.go
+++ b/internal/processing/status/create_test.go
@@ -208,6 +208,40 @@ func (suite *StatusCreateTestSuite) TestProcessMediaDescriptionTooShort() {
 	suite.Nil(apiStatus)
 }
 
+func (suite *StatusCreateTestSuite) TestProcessLanguageWithScriptPart() {
+	ctx := context.Background()
+
+	creatingAccount := suite.testAccounts["local_account_1"]
+	creatingApplication := suite.testApplications["application_1"]
+
+	statusCreateForm := &apimodel.AdvancedStatusCreateForm{
+		StatusCreateRequest: apimodel.StatusCreateRequest{
+			Status:      "你好世界", // hello world
+			MediaIDs:    []string{},
+			Poll:        nil,
+			InReplyToID: "",
+			Sensitive:   false,
+			SpoilerText: "",
+			Visibility:  apimodel.VisibilityPublic,
+			ScheduledAt: "",
+			Language:    "zh-Hans",
+			ContentType: apimodel.StatusContentTypePlain,
+		},
+		AdvancedVisibilityFlagsForm: apimodel.AdvancedVisibilityFlagsForm{
+			Federated: nil,
+			Boostable: nil,
+			Replyable: nil,
+			Likeable:  nil,
+		},
+	}
+
+	apiStatus, err := suite.status.Create(ctx, creatingAccount, creatingApplication, statusCreateForm)
+	suite.NoError(err)
+	suite.NotNil(apiStatus)
+
+	suite.Equal("zh-Hans", *apiStatus.Language)
+}
+
 func TestStatusCreateTestSuite(t *testing.T) {
 	suite.Run(t, new(StatusCreateTestSuite))
 }
diff --git a/internal/validate/formvalidation.go b/internal/validate/formvalidation.go
index 76ce6a8de..1b5996b4b 100644
--- a/internal/validate/formvalidation.go
+++ b/internal/validate/formvalidation.go
@@ -99,14 +99,19 @@ func Email(email string) error {
 	return err
 }
 
-// Language checks that the given language string is a 2- or 3-letter ISO 639 code.
-// Returns an error if the language cannot be parsed. See: https://pkg.go.dev/golang.org/x/text/language
-func Language(lang string) error {
+// Language checks that the given language string is a valid, if not necessarily canonical, BCP 47 language tag.
+// Returns a canonicalized version of the tag if the language can be parsed.
+// Returns an error if the language cannot be parsed.
+// See: https://pkg.go.dev/golang.org/x/text/language
+func Language(lang string) (string, error) {
 	if lang == "" {
-		return errors.New("no language provided")
+		return "", errors.New("no language provided")
 	}
-	_, err := language.ParseBase(lang)
-	return err
+	parsed, err := language.Parse(lang)
+	if err != nil {
+		return "", err
+	}
+	return parsed.String(), err
 }
 
 // SignUpReason checks that a sufficient reason is given for a server signup request
diff --git a/internal/validate/formvalidation_test.go b/internal/validate/formvalidation_test.go
index 534e5b849..40830407c 100644
--- a/internal/validate/formvalidation_test.go
+++ b/internal/validate/formvalidation_test.go
@@ -159,60 +159,39 @@ func (suite *ValidationTestSuite) TestValidateEmail() {
 }
 
 func (suite *ValidationTestSuite) TestValidateLanguage() {
-	empty := ""
-	notALanguage := "this isn't a language at all!"
-	english := "en"
-	capitalEnglish := "EN"
-	arabic3Letters := "ara"
-	mixedCapsEnglish := "eN"
-	englishUS := "en-us"
-	dutch := "nl"
-	german := "de"
-	var err error
-
-	err = validate.Language(empty)
-	if suite.Error(err) {
-		suite.Equal(errors.New("no language provided"), err)
-	}
-
-	err = validate.Language(notALanguage)
-	if suite.Error(err) {
-		suite.Equal(errors.New("language: tag is not well-formed"), err)
-	}
-
-	err = validate.Language(english)
-	if suite.NoError(err) {
-		suite.Equal(nil, err)
-	}
-
-	err = validate.Language(capitalEnglish)
-	if suite.NoError(err) {
-		suite.Equal(nil, err)
-	}
-
-	err = validate.Language(arabic3Letters)
-	if suite.NoError(err) {
-		suite.Equal(nil, err)
-	}
-
-	err = validate.Language(mixedCapsEnglish)
-	if suite.NoError(err) {
-		suite.Equal(nil, err)
-	}
-
-	err = validate.Language(englishUS)
-	if suite.Error(err) {
-		suite.Equal(errors.New("language: tag is not well-formed"), err)
-	}
-
-	err = validate.Language(dutch)
-	if suite.NoError(err) {
-		suite.Equal(nil, err)
-	}
-
-	err = validate.Language(german)
-	if suite.NoError(err) {
-		suite.Equal(nil, err)
+	testCases := []struct {
+		name, input, expected, err string
+	}{
+		{name: "empty", err: "no language provided"},
+		{name: "notALanguage", input: "this isn't a language at all!", err: "language: tag is not well-formed"},
+		{name: "english", input: "en", expected: "en"},
+		// Should be all lowercase
+		{name: "capitalEnglish", input: "EN", expected: "en"},
+		// Overlong, should be in ISO 639-1 format
+		{name: "arabic3Letters", input: "ara", expected: "ar"},
+		// Should be all lowercase
+		{name: "mixedCapsEnglish", input: "eN", expected: "en"},
+		// Region should be capitalized
+		{name: "englishUS", input: "en-us", expected: "en-US"},
+		{name: "dutch", input: "nl", expected: "nl"},
+		{name: "german", input: "de", expected: "de"},
+		{name: "chinese", input: "zh", expected: "zh"},
+		{name: "chineseSimplified", input: "zh-Hans", expected: "zh-Hans"},
+		{name: "chineseTraditional", input: "zh-Hant", expected: "zh-Hant"},
+	}
+
+	for _, testCase := range testCases {
+		testCase := testCase
+		suite.Run(testCase.name, func() {
+			actual, actualErr := validate.Language(testCase.input)
+			if testCase.err == "" {
+				suite.Equal(testCase.expected, actual)
+				suite.NoError(actualErr)
+			} else {
+				suite.Empty(actual)
+				suite.EqualError(actualErr, testCase.err)
+			}
+		})
 	}
 }