4 files changed, 163 insertions, 36 deletions
diff --git a/internal/gtserror/new.go b/internal/gtserror/new.go
index ad20e5cac..bb88d5f6a 100644
--- a/internal/gtserror/new.go
+++ b/internal/gtserror/new.go
@@ -18,48 +18,38 @@
 package gtserror
 
 import (
-	"errors"
 	"net/http"
-
-	"codeberg.org/gruf/go-byteutil"
 )
 
-// NewResponseError crafts an error from provided HTTP response
-// including the method, status and body (if any provided). This
-// will also wrap the returned error using WithStatusCode().
-func NewResponseError(rsp *http.Response) error {
-	var buf byteutil.Buffer
-
-	// Get URL string ahead of time.
-	urlStr := rsp.Request.URL.String()
+// New returns a new error, prepended with caller function name if gtserror.Caller is enabled.
+func New(msg string) error {
+	return newAt(3, msg)
+}
 
-	// Alloc guesstimate of required buf size.
-	buf.Guarantee(0 +
-		len(rsp.Request.Method) +
-		12 + //  request to
-		len(urlStr) +
-		17 + //  failed: status="
-		len(rsp.Status) +
-		8 + // " body="
-		256 + // max body size
-		1, // "
-	)
+// Newf returns a new formatted error, prepended with caller function name if gtserror.Caller is enabled.
+func Newf(msgf string, args ...any) error {
+	return newfAt(3, msgf, args...)
+}
 
-	// Build error message string without
+// NewResponseError crafts an error from provided HTTP response
+// including the method, status and body (if any provided). This
+// will also wrap the returned error using WithStatusCode() and
+// will include the caller function name as a prefix.
+func NewFromResponse(rsp *http.Response) error {
+	// Build error with message without
 	// using "fmt", as chances are this will
 	// be used in a hot code path and we
 	// know all the incoming types involved.
-	_, _ = buf.WriteString(rsp.Request.Method)
-	_, _ = buf.WriteString(" request to ")
-	_, _ = buf.WriteString(urlStr)
-	_, _ = buf.WriteString(" failed: status=\"")
-	_, _ = buf.WriteString(rsp.Status)
-	_, _ = buf.WriteString("\" body=\"")
-	_, _ = buf.WriteString(drainBody(rsp.Body, 256))
-	_, _ = buf.WriteString("\"")
-
-	// Create new error from msg.
-	err := errors.New(buf.String())
+	err := newAt(3, ""+
+		rsp.Request.Method+
+		" request to "+
+		rsp.Request.URL.String()+
+		" failed: status=\""+
+		rsp.Status+
+		"\" body=\""+
+		drainBody(rsp.Body, 256)+
+		"\"",
+	)
 
 	// Wrap error to provide status code.
 	return WithStatusCode(err, rsp.StatusCode)
diff --git a/internal/gtserror/new_caller.go b/internal/gtserror/new_caller.go
new file mode 100644
index 000000000..46ae76d6a
--- /dev/null
+++ b/internal/gtserror/new_caller.go
@@ -0,0 +1,92 @@
+// GoToSocial
+// Copyright (C) GoToSocial Authors admin@gotosocial.org
+// SPDX-License-Identifier: AGPL-3.0-or-later
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+//go:build !noerrcaller
+
+package gtserror
+
+import (
+	"errors"
+	"fmt"
+	"runtime"
+	"strings"
+)
+
+// Caller returns whether created errors will prepend calling function name.
+const Caller = true
+
+// cerror wraps an error with a string
+// prefix of the caller function name.
+type cerror struct {
+	c string
+	e error
+}
+
+func (ce *cerror) Error() string {
+	msg := ce.e.Error()
+	return ce.c + ": " + msg
+}
+
+func (ce *cerror) Unwrap() error {
+	return ce.e
+}
+
+// newAt is the same as New() but allows specifying calldepth.
+func newAt(calldepth int, msg string) error {
+	return &cerror{
+		c: caller(calldepth + 1),
+		e: errors.New(msg),
+	}
+}
+
+// newfAt is the same as Newf() but allows specifying calldepth.
+func newfAt(calldepth int, msgf string, args ...any) error {
+	return &cerror{
+		c: caller(calldepth + 1),
+		e: fmt.Errorf(msgf, args...),
+	}
+}
+
+// caller fetches the calling function name, skipping 'depth'. Results are cached per PC.
+func caller(depth int) string {
+	var pcs [1]uintptr
+
+	// Fetch calling function using calldepth
+	_ = runtime.Callers(depth, pcs[:])
+	fn := runtime.FuncForPC(pcs[0])
+
+	if fn == nil {
+		return ""
+	}
+
+	// Get func name.
+	name := fn.Name()
+
+	// Drop everything but but function name itself
+	if idx := strings.LastIndexByte(name, '.'); idx >= 0 {
+		name = name[idx+1:]
+	}
+
+	const params = `[...]`
+
+	// Drop any generic type parameter markers
+	if idx := strings.Index(name, params); idx >= 0 {
+		name = name[:idx] + name[idx+len(params):]
+	}
+
+	return name
+}
diff --git a/internal/gtserror/new_nocaller.go b/internal/gtserror/new_nocaller.go
new file mode 100644
index 000000000..e4eeb5ec9
--- /dev/null
+++ b/internal/gtserror/new_nocaller.go
@@ -0,0 +1,38 @@
+// GoToSocial
+// Copyright (C) GoToSocial Authors admin@gotosocial.org
+// SPDX-License-Identifier: AGPL-3.0-or-later
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+//go:build noerrcaller
+
+package gtserror
+
+import (
+	"errors"
+	"fmt"
+)
+
+// Caller returns whether created errors will prepend calling function name.
+const Caller = false
+
+// newAt is the same as New() but allows specifying calldepth.
+func newAt(_ int, msg string) error {
+	return errors.New(msg)
+}
+
+// newfAt is the same as Newf() but allows specifying calldepth.
+func newfAt(_ int, msgf string, args ...any) error {
+	return fmt.Errorf(msgf, args...)
+}
diff --git a/internal/gtserror/new_test.go b/internal/gtserror/new_test.go
index b0824b5a7..8b4dae1ba 100644
--- a/internal/gtserror/new_test.go
+++ b/internal/gtserror/new_test.go
@@ -10,6 +10,7 @@ import (
 	"testing"
 
 	"github.com/superseriousbusiness/gotosocial/internal/gtserror"
+	"github.com/superseriousbusiness/gotosocial/internal/log"
 )
 
 func TestResponseError(t *testing.T) {
@@ -53,13 +54,19 @@ func testResponseError(t *testing.T, rsp http.Response) {
 		body = string(b[:trunc])
 	}
 	expect := fmt.Sprintf(
-		"%s request to %s failed: status=\"%s\" body=\"%s\"",
+		"%s%s request to %s failed: status=\"%s\" body=\"%s\"",
+		func() string {
+			if gtserror.Caller {
+				return strings.Split(log.Caller(3), ".")[1] + ": "
+			}
+			return ""
+		}(),
 		rsp.Request.Method,
 		rsp.Request.URL.String(),
 		rsp.Status,
 		body,
 	)
-	err := gtserror.NewResponseError(&rsp)
+	err := gtserror.NewFromResponse(&rsp)
 	if str := err.Error(); str != expect {
 		t.Errorf("unexpected error string: recv=%q expct=%q", str, expect)
 	}