feat(build): add support for the base.Messenger, $.locale.Tr, Form structs to lint-locale-usage (#9095)

- Move a file around to avoid a circular dependency.
- Make lint-locale-usage aware of `base.Messenger`, form struct tags and `$.locale.Tr`.

Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/9095
Reviewed-by: Gusted <gusted@noreply.codeberg.org>
Co-authored-by: Ellen Εμιλία Άννα Zscheile <fogti+devel@ytrizja.de>
Co-committed-by: Ellen Εμιλία Άννα Zscheile <fogti+devel@ytrizja.de>

CODEOWNERS

@@ -38,6 +38,10 @@ routers/.* @gusted
 options/locale/.* @0ko
 options/locale_next/.* @0ko
 
-# Personal interest
+# lint-locale-usage
 build/lint-locale-usage/.* @fogti
+models/unit/.* @fogti
+services/migrations/lint-locale-usage/.* @fogti
+
+# Personal interest
 .*/webhook.* @oliverpool

Makefile

@@ -475,7 +475,7 @@ lint-locale:
 
 .PHONY: lint-locale-usage
 lint-locale-usage:
-	$(GO) run ./build/lint-locale-usage --allow-masked-usages-from=build/lint-locale-usage/allowed-masked-usage.txt
+	$(GO) run ./build/lint-locale-usage/bin --allow-masked-usages-from=build/lint-locale-usage/allowed-masked-usage.txt
 
 .PHONY: lint-md
 lint-md: node_modules

build/lint-locale-usage/allowed-masked-usage.txt

@@ -23,12 +23,6 @@ themes.names.
 # services/context/context.go
 relativetime.
 
-# templates/mail/issue/default.tmpl: $.locale.Tr
-mail.issue.in_tree_path
-
-# templates/package/metadata/arch.tmpl: $.locale.Tr
-packages.details.license
-
 # templates/repo/issue/view_content.tmpl: indirection via $closeTranslationKey
 repo.issues.close
 repo.pulls.close
@@ -48,7 +42,3 @@ projects.type-3.display_name
 # templates/repo/settings/webhook/link_menu.tmpl, templates/webhook/new.tmpl: repo.settings.web_hook_name_
 # tests/integration/repo_archive_text_test.go
 repo.settings.
-
-# services/migrations/migrate.go: messenger calls
-# ToDo: give them a unique prefix
-repo.migrate.

build/lint-locale-usage/bin/handle-go.go

@@ -0,0 +1,177 @@
+// Copyright 2023 The Gitea Authors. All rights reserved.
+// Copyright 2025 The Forgejo Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package main
+
+import (
+	"fmt"
+	"go/ast"
+	goParser "go/parser"
+	"go/token"
+	"reflect"
+	"slices"
+	"strconv"
+	"strings"
+
+	llu "forgejo.org/build/lint-locale-usage"
+	lluUnit "forgejo.org/models/unit/lint-locale-usage"
+	lluMigrate "forgejo.org/services/migrations/lint-locale-usage"
+)
+
+// the `Handle*File` functions follow the following calling convention:
+// * `fname` is the name of the input file
+// * `src` is either `nil` (then the function invokes `ReadFile` to read the file)
+//   or the contents of the file as {`[]byte`, or a `string`}
+
+func HandleGoFile(handler llu.Handler, fname string, src any) error {
+	fset := token.NewFileSet()
+	node, err := goParser.ParseFile(fset, fname, src, goParser.SkipObjectResolution|goParser.ParseComments)
+	if err != nil {
+		return llu.LocatedError{
+			Location: fname,
+			Kind:     "Go parser",
+			Err:      err,
+		}
+	}
+
+	ast.Inspect(node, func(n ast.Node) bool {
+		// search for function calls of the form `anything.Tr(any-string-lit, ...)`
+
+		switch n2 := n.(type) {
+		case *ast.CallExpr:
+			if len(n2.Args) == 0 {
+				return true
+			}
+			funSel, ok := n2.Fun.(*ast.SelectorExpr)
+			if !ok {
+				return true
+			}
+
+			ltf, ok := handler.LocaleTrFunctions[funSel.Sel.Name]
+			if !ok {
+				return true
+			}
+
+			var gotUnexpectedInvoke *int
+
+			for _, argNum := range ltf {
+				if len(n2.Args) <= int(argNum) {
+					argc := len(n2.Args)
+					gotUnexpectedInvoke = &argc
+				} else {
+					handler.HandleGoTrArgument(fset, n2.Args[int(argNum)], "")
+				}
+			}
+
+			if gotUnexpectedInvoke != nil {
+				handler.OnUnexpectedInvoke(fset, funSel.Sel.NamePos, funSel.Sel.Name, *gotUnexpectedInvoke)
+			}
+
+		case *ast.CompositeLit:
+			if strings.HasSuffix(fname, "models/unit/unit.go") {
+				lluUnit.HandleCompositeUnit(handler, fset, n2)
+			}
+
+		case *ast.FuncDecl:
+			matchInsPrefix := handler.HandleGoCommentGroup(fset, n2.Doc, "llu:returnsTrKey")
+			if matchInsPrefix != nil {
+				results := n2.Type.Results.List
+				if len(results) != 1 {
+					handler.OnWarning(fset, n2.Type.Func, fmt.Sprintf("function %s has unexpected return type; expected single return value", n2.Name.Name))
+					return true
+				}
+
+				ast.Inspect(n2.Body, func(n ast.Node) bool {
+					// search for return stmts
+					// TODO: what about nested functions?
+					if ret, ok := n.(*ast.ReturnStmt); ok {
+						for _, res := range ret.Results {
+							ast.Inspect(res, func(n ast.Node) bool {
+								if expr, ok := n.(ast.Expr); ok {
+									handler.HandleGoTrArgument(fset, expr, *matchInsPrefix)
+								}
+								return true
+							})
+						}
+						return false
+					}
+					return true
+				})
+			}
+
+			if strings.HasSuffix(fname, "services/migrations/migrate.go") {
+				lluMigrate.HandleMessengerInFunc(handler, fset, n2)
+			}
+			return true
+		case *ast.GenDecl:
+			switch n2.Tok {
+			case token.CONST, token.VAR:
+				matchInsPrefix := handler.HandleGoCommentGroup(fset, n2.Doc, " llu:TrKeys")
+				if matchInsPrefix == nil {
+					return true
+				}
+				for _, spec := range n2.Specs {
+					// interpret all contained strings as message IDs
+					ast.Inspect(spec, func(n ast.Node) bool {
+						if argLit, ok := n.(*ast.BasicLit); ok {
+							handler.HandleGoTrBasicLit(fset, argLit, *matchInsPrefix)
+							return false
+						}
+						return true
+					})
+				}
+
+			case token.TYPE:
+				// modules/web/middleware/binding.go:Validate uses the convention that structs
+				// entries can have tags.
+				// In particular, `locale:$msgid` should be handled; any fields with `form:-` shouldn't.
+				// Problem: we don't know which structs are forms, actually.
+
+				for _, spec := range n2.Specs {
+					tspec := spec.(*ast.TypeSpec)
+					structNode, ok := tspec.Type.(*ast.StructType)
+					if !ok || !(strings.HasSuffix(tspec.Name.Name, "Form") ||
+						(tspec.Doc != nil &&
+							slices.ContainsFunc(tspec.Doc.List, func(c *ast.Comment) bool {
+								return c.Text == "// swagger:model"
+							}))) {
+						continue
+					}
+					for _, field := range structNode.Fields.List {
+						if field.Names == nil {
+							continue
+						}
+						if len(field.Names) != 1 {
+							handler.OnWarning(fset, field.Type.Pos(), "unsupported multiple field names")
+							continue
+						}
+						msgidPos := field.Names[0].NamePos
+						msgid := "form." + field.Names[0].Name
+						if field.Tag != nil && field.Tag.Kind == token.STRING {
+							rawTag, err := strconv.Unquote(field.Tag.Value)
+							if err != nil {
+								handler.OnWarning(fset, field.Tag.ValuePos, "invalid tag value encountered")
+								continue
+							}
+							tag := reflect.StructTag(rawTag)
+							if tag.Get("form") == "-" {
+								continue
+							}
+							tmp := tag.Get("locale")
+							if len(tmp) != 0 {
+								msgidPos = field.Tag.ValuePos
+								msgid = tmp
+							}
+						}
+						handler.OnMsgid(fset, msgidPos, msgid, true)
+					}
+				}
+			}
+		}
+
+		return true
+	})
+
+	return nil
+}

build/lint-locale-usage/bin/lint-locale-usage.go

@@ -16,6 +16,7 @@ import (
 	"sort"
 	"strings"
 
+	llu "forgejo.org/build/lint-locale-usage"
 	"forgejo.org/modules/container"
 	"forgejo.org/modules/translation/localeiter"
 )
@@ -23,27 +24,6 @@ import (
 // this works by first gathering all valid source string IDs from `en-US` reference files
 // and then checking if all used source strings are actually defined
 
-type LocatedError struct {
-	Location string
-	Kind     string
-	Err      error
-}
-
-func (e LocatedError) Error() string {
-	var sb strings.Builder
-
-	sb.WriteString(e.Location)
-	sb.WriteString(":\t")
-	if e.Kind != "" {
-		sb.WriteString(e.Kind)
-		sb.WriteString(": ")
-	}
-	sb.WriteString("ERROR: ")
-	sb.WriteString(e.Err.Error())
-
-	return sb.String()
-}
-
 func InitLocaleTrFunctions() map[string][]uint {
 	ret := make(map[string][]uint)
 
@@ -58,14 +38,6 @@ func InitLocaleTrFunctions() map[string][]uint {
 	return ret
 }
 
-type Handler struct {
-	OnMsgid            func(fset *token.FileSet, pos token.Pos, msgid string)
-	OnMsgidPrefix      func(fset *token.FileSet, pos token.Pos, msgidPrefix string, truncated bool)
-	OnUnexpectedInvoke func(fset *token.FileSet, pos token.Pos, funcname string, argc int)
-	OnWarning          func(fset *token.FileSet, pos token.Pos, msg string)
-	LocaleTrFunctions  map[string][]uint
-}
-
 type StringTrie interface {
 	Matches(key []string) bool
 }
@@ -113,7 +85,7 @@ func (m StringTrieMap) Insert(key []string) {
 func ParseAllowedMaskedUsages(fname string, usedMsgids container.Set[string], allowedMaskedPrefixes StringTrieMap, chkMsgid func(msgid string) bool) error {
 	file, err := os.Open(fname)
 	if err != nil {
-		return LocatedError{
+		return llu.LocatedError{
 			Location: fname,
 			Kind:     "Open",
 			Err:      err,
@@ -133,7 +105,7 @@ func ParseAllowedMaskedUsages(fname string, usedMsgids container.Set[string], al
 			allowedMaskedPrefixes.Insert(strings.Split(linePrefix, "."))
 		} else {
 			if !chkMsgid(line) {
-				return LocatedError{
+				return llu.LocatedError{
 					Location: fmt.Sprintf("%s: line %d", fname, lno),
 					Kind:     "undefined msgid",
 					Err:      errors.New(line),
@@ -143,7 +115,7 @@ func ParseAllowedMaskedUsages(fname string, usedMsgids container.Set[string], al
 		}
 	}
 	if err := scanner.Err(); err != nil {
-		return LocatedError{
+		return llu.LocatedError{
 			Location: fname,
 			Kind:     "Scanner",
 			Err:      err,
@@ -152,15 +124,6 @@ func ParseAllowedMaskedUsages(fname string, usedMsgids container.Set[string], al
 	return nil
 }
 
-// Truncating a message id prefix to the last dot
-func PrepareMsgidPrefix(s string) (string, bool) {
-	index := strings.LastIndexByte(s, 0x2e)
-	if index == -1 {
-		return "", true
-	}
-	return s[:index], index != len(s)-1
-}
-
 func Usage() {
 	outp := flag.CommandLine.Output()
 	fmt.Fprintf(outp, "Usage of %s:\n", os.Args[0])
@@ -210,6 +173,7 @@ func Usage() {
 func main() {
 	allowMissingMsgids := false
 	allowUnusedMsgids := false
+	allowWeakMissingMsgids := true
 	usedMsgids := make(container.Set[string])
 	allowedMaskedPrefixes := make(StringTrieMap)
 
@@ -228,6 +192,12 @@ func main() {
 		false,
 		"don't return an error code if missing message IDs are found",
 	)
+	flag.BoolVar(
+		&allowWeakMissingMsgids,
+		"allow-weak-missing-msgids",
+		true,
+		"Don't return an error code if missing 'weak' (e.g. \"form.$msgid\") message IDs are found",
+	)
 	flag.BoolVar(
 		&allowUnusedMsgids,
 		"allow-unused-msgids",
@@ -289,7 +259,7 @@ func main() {
 		os.Exit(3)
 	}
 
-	handler := Handler{
+	handler := llu.Handler{
 		OnMsgidPrefix: func(fset *token.FileSet, pos token.Pos, msgidPrefix string, truncated bool) {
 			msgidPrefixSplit := strings.Split(msgidPrefix, ".")
 			if !truncated {
@@ -299,8 +269,11 @@ func main() {
 				fmt.Printf("%s:\tmissing msgid prefix: %s\n", fset.Position(pos).String(), msgidPrefix)
 			}
 		},
-		OnMsgid: func(fset *token.FileSet, pos token.Pos, msgid string) {
+		OnMsgid: func(fset *token.FileSet, pos token.Pos, msgid string, weak bool) {
 			if !msgids.Contains(msgid) {
+				if weak && allowWeakMissingMsgids {
+					return
+				}
 				gotAnyMsgidError = true
 				fmt.Printf("%s:\tmissing msgid: %s\n", fset.Position(pos).String(), msgid)
 			} else {
@@ -314,7 +287,7 @@ func main() {
 		OnWarning: func(fset *token.FileSet, pos token.Pos, msg string) {
 			fmt.Printf("%s:\tWARNING: %s\n", fset.Position(pos).String(), msg)
 		},
-		LocaleTrFunctions: InitLocaleTrFunctions(),
+		LocaleTrFunctions: llu.InitLocaleTrFunctions(),
 	}
 
 	if err := filepath.WalkDir(".", func(fpath string, d fs.DirEntry, err error) error {
@@ -332,7 +305,7 @@ func main() {
 		} else if name == "bindata.go" || fpath == "modules/translation/i18n/i18n_test.go" {
 			// skip false positives
 		} else if strings.HasSuffix(name, ".go") {
-			onError(handler.HandleGoFile(fpath, nil))
+			onError(HandleGoFile(handler, fpath, nil))
 		} else if strings.HasSuffix(name, ".tmpl") {
 			if strings.HasPrefix(fpath, "tests") && strings.HasSuffix(name, ".ini.tmpl") {
 				// skip false positives

build/lint-locale-usage/bin/lint-locale-usage_test.go

@@ -7,24 +7,26 @@ import (
 	"go/token"
 	"testing"
 
+	llu "forgejo.org/build/lint-locale-usage"
+
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 )
 
-func buildHandler(ret *[]string) Handler {
-	return Handler{
-		OnMsgid: func(fset *token.FileSet, pos token.Pos, msgid string) {
+func buildHandler(ret *[]string) llu.Handler {
+	return llu.Handler{
+		OnMsgid: func(fset *token.FileSet, pos token.Pos, msgid string, weak bool) {
 			*ret = append(*ret, msgid)
 		},
 		OnUnexpectedInvoke: func(fset *token.FileSet, pos token.Pos, funcname string, argc int) {},
-		LocaleTrFunctions:  InitLocaleTrFunctions(),
+		LocaleTrFunctions:  llu.InitLocaleTrFunctions(),
 	}
 }
 
 func HandleGoFileWrapped(t *testing.T, fname, src string) []string {
 	var ret []string
 	handler := buildHandler(&ret)
-	require.NoError(t, handler.HandleGoFile(fname, src))
+	require.NoError(t, HandleGoFile(handler, fname, src))
 	return ret
 }
 

build/lint-locale-usage/handle-go.go

@@ -2,18 +2,17 @@
 // Copyright 2025 The Forgejo Authors. All rights reserved.
 // SPDX-License-Identifier: MIT
 
-package main
+package lintLocaleUsage
 
 import (
 	"fmt"
 	"go/ast"
-	goParser "go/parser"
 	"go/token"
 	"strconv"
 	"strings"
 )
 
-func (handler Handler) handleGoTrBasicLit(fset *token.FileSet, argLit *ast.BasicLit, prefix string) {
+func (handler Handler) HandleGoTrBasicLit(fset *token.FileSet, argLit *ast.BasicLit, prefix string) {
 	if argLit.Kind == token.STRING {
 		// extract string content
 		arg, err := strconv.Unquote(argLit.Value)
@@ -29,14 +28,14 @@ func (handler Handler) handleGoTrBasicLit(fset *token.FileSet, argLit *ast.Basic
 			}
 			handler.OnMsgidPrefix(fset, argLit.ValuePos, prep, trunc)
 		} else {
-			handler.OnMsgid(fset, argLit.ValuePos, arg)
+			handler.OnMsgid(fset, argLit.ValuePos, arg, false)
 		}
 	}
 }
 
-func (handler Handler) handleGoTrArgument(fset *token.FileSet, n ast.Expr, prefix string) {
+func (handler Handler) HandleGoTrArgument(fset *token.FileSet, n ast.Expr, prefix string) {
 	if argLit, ok := n.(*ast.BasicLit); ok {
-		handler.handleGoTrBasicLit(fset, argLit, prefix)
+		handler.HandleGoTrBasicLit(fset, argLit, prefix)
 	} else if argBinExpr, ok := n.(*ast.BinaryExpr); ok {
 		if argBinExpr.Op != token.ADD {
 			// pass
@@ -57,7 +56,7 @@ func (handler Handler) handleGoTrArgument(fset *token.FileSet, n ast.Expr, prefi
 	}
 }
 
-func (handler Handler) handleGoCommentGroup(fset *token.FileSet, cg *ast.CommentGroup, commentPrefix string) *string {
+func (handler Handler) HandleGoCommentGroup(fset *token.FileSet, cg *ast.CommentGroup, commentPrefix string) *string {
 	if cg == nil {
 		return nil
 	}
@@ -87,131 +86,3 @@ func (handler Handler) handleGoCommentGroup(fset *token.FileSet, cg *ast.Comment
 		return &matchInsPrefix
 	}
 }
-
-// the `Handle*File` functions follow the following calling convention:
-// * `fname` is the name of the input file
-// * `src` is either `nil` (then the function invokes `ReadFile` to read the file)
-//   or the contents of the file as {`[]byte`, or a `string`}
-
-func (handler Handler) HandleGoFile(fname string, src any) error {
-	fset := token.NewFileSet()
-	node, err := goParser.ParseFile(fset, fname, src, goParser.SkipObjectResolution|goParser.ParseComments)
-	if err != nil {
-		return LocatedError{
-			Location: fname,
-			Kind:     "Go parser",
-			Err:      err,
-		}
-	}
-
-	ast.Inspect(node, func(n ast.Node) bool {
-		// search for function calls of the form `anything.Tr(any-string-lit, ...)`
-
-		switch n2 := n.(type) {
-		case *ast.CallExpr:
-			if len(n2.Args) == 0 {
-				return true
-			}
-			funSel, ok := n2.Fun.(*ast.SelectorExpr)
-			if !ok {
-				return true
-			}
-
-			ltf, ok := handler.LocaleTrFunctions[funSel.Sel.Name]
-			if !ok {
-				return true
-			}
-
-			var gotUnexpectedInvoke *int
-
-			for _, argNum := range ltf {
-				if len(n2.Args) <= int(argNum) {
-					argc := len(n2.Args)
-					gotUnexpectedInvoke = &argc
-				} else {
-					handler.handleGoTrArgument(fset, n2.Args[int(argNum)], "")
-				}
-			}
-
-			if gotUnexpectedInvoke != nil {
-				handler.OnUnexpectedInvoke(fset, funSel.Sel.NamePos, funSel.Sel.Name, *gotUnexpectedInvoke)
-			}
-		case *ast.CompositeLit:
-			ident, ok := n2.Type.(*ast.Ident)
-			if !ok {
-				return true
-			}
-
-			// special case: models/unit/unit.go
-			if strings.HasSuffix(fname, "unit.go") && ident.Name == "Unit" {
-				if len(n2.Elts) != 6 {
-					handler.OnWarning(fset, n2.Pos(), "unexpected initialization of 'Unit' (unexpected number of arguments)")
-				}
-				// NameKey has index 2
-				//   invoked like '{{ctx.Locale.Tr $unit.NameKey}}'
-				nameKey, ok := n2.Elts[2].(*ast.BasicLit)
-				if !ok || nameKey.Kind != token.STRING {
-					handler.OnWarning(fset, n2.Elts[2].Pos(), "unexpected initialization of 'Unit' (expected string literal as NameKey)")
-					return true
-				}
-
-				// extract string content
-				arg, err := strconv.Unquote(nameKey.Value)
-				if err == nil {
-					// found interesting strings
-					handler.OnMsgid(fset, nameKey.ValuePos, arg)
-				}
-			}
-		case *ast.FuncDecl:
-			matchInsPrefix := handler.handleGoCommentGroup(fset, n2.Doc, "llu:returnsTrKey")
-			if matchInsPrefix == nil {
-				return true
-			}
-			results := n2.Type.Results.List
-			if len(results) != 1 {
-				handler.OnWarning(fset, n2.Type.Func, fmt.Sprintf("function %s has unexpected return type; expected single return value", n2.Name.Name))
-				return true
-			}
-
-			ast.Inspect(n2.Body, func(n ast.Node) bool {
-				// search for return stmts
-				// TODO: what about nested functions?
-				if ret, ok := n.(*ast.ReturnStmt); ok {
-					for _, res := range ret.Results {
-						ast.Inspect(res, func(n ast.Node) bool {
-							if expr, ok := n.(ast.Expr); ok {
-								handler.handleGoTrArgument(fset, expr, *matchInsPrefix)
-							}
-							return true
-						})
-					}
-					return false
-				}
-				return true
-			})
-			return true
-		case *ast.GenDecl:
-			if !(n2.Tok == token.CONST || n2.Tok == token.VAR) {
-				return true
-			}
-			matchInsPrefix := handler.handleGoCommentGroup(fset, n2.Doc, " llu:TrKeys")
-			if matchInsPrefix == nil {
-				return true
-			}
-			for _, spec := range n2.Specs {
-				// interpret all contained strings as message IDs
-				ast.Inspect(spec, func(n ast.Node) bool {
-					if argLit, ok := n.(*ast.BasicLit); ok {
-						handler.handleGoTrBasicLit(fset, argLit, *matchInsPrefix)
-						return false
-					}
-					return true
-				})
-			}
-		}
-
-		return true
-	})
-
-	return nil
-}

build/lint-locale-usage/handle-tmpl.go

@@ -2,7 +2,7 @@
 // Copyright 2025 The Forgejo Authors. All rights reserved.
 // SPDX-License-Identifier: MIT
 
-package main
+package lintLocaleUsage
 
 import (
 	"fmt"
@@ -48,18 +48,29 @@ func (handler Handler) handleTemplateNode(fset *token.FileSet, node tmplParser.N
 		}
 
 		funcname := ""
-		if nodeChain, ok := nodeCommand.Args[0].(*tmplParser.ChainNode); ok {
+		switch nodeCommand.Args[0].Type() {
+		case tmplParser.NodeChain:
+			nodeChain := nodeCommand.Args[0].(*tmplParser.ChainNode)
 			if nodeIdent, ok := nodeChain.Node.(*tmplParser.IdentifierNode); ok {
 				if nodeIdent.Ident != "ctx" || len(nodeChain.Field) != 2 || nodeChain.Field[0] != "Locale" {
 					return
 				}
 				funcname = nodeChain.Field[1]
 			}
-		} else if nodeField, ok := nodeCommand.Args[0].(*tmplParser.FieldNode); ok {
+
+		case tmplParser.NodeField:
+			nodeField := nodeCommand.Args[0].(*tmplParser.FieldNode)
 			if len(nodeField.Ident) != 2 || !(nodeField.Ident[0] == "locale" || nodeField.Ident[0] == "Locale") {
 				return
 			}
 			funcname = nodeField.Ident[1]
+
+		case tmplParser.NodeVariable:
+			nodeVar := nodeCommand.Args[0].(*tmplParser.VariableNode)
+			if len(nodeVar.Ident) != 3 || !(nodeVar.Ident[0] == "$" && nodeVar.Ident[1] == "locale") {
+				return
+			}
+			funcname = nodeVar.Ident[2]
 		}
 
 		var gotUnexpectedInvoke *int
@@ -93,7 +104,7 @@ func (handler Handler) handleTemplateMsgid(fset *token.FileSet, node tmplParser.
 	case tmplParser.NodeString:
 		nodeString := node.(*tmplParser.StringNode)
 		// found interesting strings
-		handler.OnMsgid(fset, pos, nodeString.Text)
+		handler.OnMsgid(fset, pos, nodeString.Text, false)
 
 	case tmplParser.NodePipe:
 		nodePipe := node.(*tmplParser.PipeNode)
@@ -132,7 +143,7 @@ func (handler Handler) handleTemplateMsgid(fset *token.FileSet, node tmplParser.
 
 		if len(nodeCommand.Args) == 2 {
 			// found interesting strings
-			handler.OnMsgid(fset, stringPos, msgidPrefix)
+			handler.OnMsgid(fset, stringPos, msgidPrefix, false)
 		} else {
 			if nodeIdent.Ident == "printf" {
 				parts := strings.SplitN(msgidPrefix, "%", 2)

build/lint-locale-usage/handler.go

@@ -0,0 +1,62 @@
+// Copyright 2023 The Gitea Authors. All rights reserved.
+// Copyright 2025 The Forgejo Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package lintLocaleUsage
+
+import (
+	"go/token"
+	"strings"
+)
+
+type LocatedError struct {
+	Location string
+	Kind     string
+	Err      error
+}
+
+func (e LocatedError) Error() string {
+	var sb strings.Builder
+
+	sb.WriteString(e.Location)
+	sb.WriteString(":\t")
+	if e.Kind != "" {
+		sb.WriteString(e.Kind)
+		sb.WriteString(": ")
+	}
+	sb.WriteString("ERROR: ")
+	sb.WriteString(e.Err.Error())
+
+	return sb.String()
+}
+
+func InitLocaleTrFunctions() map[string][]uint {
+	ret := make(map[string][]uint)
+
+	f0 := []uint{0}
+	ret["Tr"] = f0
+	ret["TrString"] = f0
+	ret["TrHTML"] = f0
+
+	ret["TrPluralString"] = []uint{1}
+	ret["TrN"] = []uint{1, 2}
+
+	return ret
+}
+
+type Handler struct {
+	OnMsgid            func(fset *token.FileSet, pos token.Pos, msgid string, weak bool)
+	OnMsgidPrefix      func(fset *token.FileSet, pos token.Pos, msgidPrefix string, truncated bool)
+	OnUnexpectedInvoke func(fset *token.FileSet, pos token.Pos, funcname string, argc int)
+	OnWarning          func(fset *token.FileSet, pos token.Pos, msg string)
+	LocaleTrFunctions  map[string][]uint
+}
+
+// Truncating a message id prefix to the last dot
+func PrepareMsgidPrefix(s string) (string, bool) {
+	index := strings.LastIndexByte(s, 0x2e)
+	if index == -1 {
+		return "", true
+	}
+	return s[:index], index != len(s)-1
+}

models/unit/lint-locale-usage/llu.go

@@ -0,0 +1,38 @@
+// Copyright 2025 The Forgejo Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package lintLocaleUsage
+
+import (
+	"go/ast"
+	"go/token"
+	"strconv"
+
+	llu "forgejo.org/build/lint-locale-usage"
+)
+
+func HandleCompositeUnit(handler llu.Handler, fset *token.FileSet, n *ast.CompositeLit) {
+	ident, ok := n.Type.(*ast.Ident)
+	if !ok || ident.Name != "Unit" {
+		return
+	}
+
+	if len(n.Elts) != 6 {
+		handler.OnWarning(fset, n.Pos(), "unexpected initialization of 'Unit' (unexpected number of arguments)")
+		return
+	}
+	// NameKey has index 2
+	//   invoked like '{{ctx.Locale.Tr $unit.NameKey}}'
+	nameKey, ok := n.Elts[2].(*ast.BasicLit)
+	if !ok || nameKey.Kind != token.STRING {
+		handler.OnWarning(fset, n.Elts[2].Pos(), "unexpected initialization of 'Unit' (expected string literal as NameKey)")
+		return
+	}
+
+	// extract string content
+	arg, err := strconv.Unquote(nameKey.Value)
+	if err == nil {
+		// found interesting strings
+		handler.OnMsgid(fset, nameKey.ValuePos, arg, false)
+	}
+}

services/migrations/lint-locale-usage/llu.go

@@ -0,0 +1,45 @@
+// Copyright 2025 The Forgejo Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package lintLocaleUsage
+
+import (
+	"go/ast"
+	"go/token"
+
+	llu "forgejo.org/build/lint-locale-usage"
+	"forgejo.org/modules/container"
+)
+
+// special case: services/migrations/migrate.go
+func HandleMessengerInFunc(handler llu.Handler, fset *token.FileSet, n2 *ast.FuncDecl) {
+	messenger := make(container.Set[string])
+	for _, i := range n2.Type.Params.List {
+		if ret, ok := i.Type.(*ast.SelectorExpr); ok && ret.Sel.Name == "Messenger" {
+			if ret, ok := ret.X.(*ast.Ident); ok && ret.Name == "base" {
+				for _, j := range i.Names {
+					messenger.Add(j.Name)
+				}
+			}
+		}
+	}
+	if len(messenger) == 0 {
+		return
+	}
+	ast.Inspect(n2.Body, func(n ast.Node) bool {
+		// search for "messenger" function calls
+		call, ok := n.(*ast.CallExpr)
+		if !ok {
+			return true
+		}
+		if ret, ok := call.Fun.(*ast.Ident); !(ok && messenger.Contains(ret.Name)) {
+			return true
+		}
+		if len(call.Args) != 1 {
+			handler.OnWarning(fset, call.Lparen, "unexpected invocation of base.Messenger (expected exactly 1 argument)")
+			return true
+		}
+		handler.HandleGoTrArgument(fset, call.Args[0], "")
+		return true
+	})
+}