refactor(logging): add a logging abstraction and move the job logger onto it (#1295)

Add `act/common/logging`: a printf-style `Logger` on a slog-shaped `Handler`, with a logrus-backed handler as the only backend, plus a `logtest` handler for tests. Move the job logger onto it: `common.Logger` returns `*logging.Logger`, the job log formatters and the `Reporter` hook become handlers, and composite step IDs travel in the context.

Logging is tightly coupled to logrus types (hooks, formatters, `Entry.Data`). Going through our own interface first lets the remaining call sites move over with unchanged behavior, and lets the backend be swapped for `log/slog` in one place afterwards. The global process logger and its masking formatter stay on logrus for now.

Assisted-by: Codet
Co-authored-by: bircni <[email protected]>
Reviewed-on: https://gitea.com/gitea/runner/pulls/1295
Reviewed-by: bircni <[email protected]>

act/common/logging/handler.go

@@ -0,0 +1,114 @@
+// Copyright 2026 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package logging
+
+import (
+	"context"
+	"errors"
+	"slices"
+	"time"
+)
+
+// Attr is a structured key/value pair attached to a log record.
+type Attr struct {
+	Key   string
+	Value any
+}
+
+// Record is one log event. Attrs holds the call-site attributes only, the ones added with
+// Logger.With are accumulated by the Handler.
+type Record struct {
+	Time    time.Time
+	Level   Level
+	Message string
+	PC      uintptr // program counter of the logging call, 0 if unknown
+	Attrs   []Attr
+}
+
+// Attr returns the value of the last attribute named key.
+func (r Record) Attr(key string) (any, bool) {
+	for _, a := range slices.Backward(r.Attrs) {
+		if a.Key == key {
+			return a.Value, true
+		}
+	}
+	return nil, false
+}
+
+// Handler consumes records, and is shaped like slog.Handler so that a slog backend can replace
+// the current one without touching callers. Handle must not modify the Attrs slice it is given.
+type Handler interface {
+	Enabled(ctx context.Context, level Level) bool
+	Handle(ctx context.Context, r Record) error
+	// WithAttrs returns a Handler that adds attrs to every record it handles.
+	WithAttrs(attrs []Attr) Handler
+}
+
+type multiHandler []Handler
+
+// NewMultiHandler fans every record out to all handlers that have its level enabled.
+func NewMultiHandler(handlers ...Handler) Handler {
+	return multiHandler(handlers)
+}
+
+func (m multiHandler) Enabled(ctx context.Context, level Level) bool {
+	for _, h := range m {
+		if h.Enabled(ctx, level) {
+			return true
+		}
+	}
+	return false
+}
+
+func (m multiHandler) Handle(ctx context.Context, r Record) error {
+	var errs []error
+	for _, h := range m {
+		if h.Enabled(ctx, r.Level) {
+			errs = append(errs, h.Handle(ctx, r))
+		}
+	}
+	return errors.Join(errs...)
+}
+
+func (m multiHandler) WithAttrs(attrs []Attr) Handler {
+	out := make(multiHandler, len(m))
+	for i, h := range m {
+		out[i] = h.WithAttrs(attrs)
+	}
+	return out
+}
+
+type discardHandler struct{}
+
+// DiscardHandler drops every record.
+var DiscardHandler Handler = discardHandler{}
+
+func (discardHandler) Enabled(context.Context, Level) bool  { return false }
+func (discardHandler) Handle(context.Context, Record) error { return nil }
+func (d discardHandler) WithAttrs([]Attr) Handler           { return d }
+
+type levelHandler struct {
+	h        Handler
+	minLevel Level
+}
+
+// NewLevelHandler passes only records at or above minLevel on to h.
+func NewLevelHandler(h Handler, minLevel Level) Handler {
+	return levelHandler{h: h, minLevel: minLevel}
+}
+
+func (l levelHandler) Enabled(ctx context.Context, level Level) bool {
+	return level >= l.minLevel && l.h.Enabled(ctx, level)
+}
+
+func (l levelHandler) Handle(ctx context.Context, r Record) error {
+	if r.Level < l.minLevel {
+		return nil
+	}
+	return l.h.Handle(ctx, r)
+}
+
+func (l levelHandler) WithAttrs(attrs []Attr) Handler {
+	return levelHandler{h: l.h.WithAttrs(attrs), minLevel: l.minLevel}
+}