fix(capture): accept a bare pipeline string in video pipelines entries (#701)

* fix(capture): accept a bare pipeline string in video pipelines entries

NEKO_CAPTURE_VIDEO_PIPELINES expects every entry to be a full pipeline config
object, but the singular capture.video.pipeline option trains people to write
the whole pipeline as a plain string, so a dict like {"high": "ximagesrc ...
! appsink"} failed to unmarshal, the error got reduced to a warn and neko fell
back to the default vp8 pipeline silently, also overriding a directly set
video codec

the json string hook decodes the env value into a generic map, so the shorthand
is restored in the mapstructure chain: a string value for an entry now becomes
VideoConfig{GstPipeline: ...}, the same shape the single pipeline option
produces, object entries are untouched

the new config test drives the production env flow (Init + Set) and fails on
master with the same two warnings the reporter saw

Fixes #689

* feat(capture): add shorthand support for pipeline entries as plain strings.

---------

Co-authored-by: Miroslav Šedivý <sedivy.miro@gmail.com>

server/internal/config/capture.go

@@ -2,8 +2,10 @@ package config
 
 import (
 	"os"
+	"reflect"
 	"strings"
 
+	"github.com/go-viper/mapstructure/v2"
 	"github.com/pion/webrtc/v4"
 	"github.com/rs/zerolog/log"
 	"github.com/spf13/cobra"
@@ -322,6 +324,17 @@ func (Capture) InitV2(cmd *cobra.Command) error {
 	return nil
 }
 
+// videoPipelineShorthandHook accepts a bare pipeline string in place of a full
+// video pipeline config, mirroring the capture.video.pipeline shorthand.
+func videoPipelineShorthandHook() mapstructure.DecodeHookFunc {
+	return func(from reflect.Type, to reflect.Type, data any) (any, error) {
+		if from.Kind() == reflect.String && to == reflect.TypeOf(types.VideoConfig{}) {
+			return types.VideoConfig{GstPipeline: data.(string)}, nil
+		}
+		return data, nil
+	}
+}
+
 func (s *Capture) Set() {
 	var ok bool
 
@@ -342,7 +355,10 @@ func (s *Capture) Set() {
 
 	s.VideoIDs = viper.GetStringSlice("capture.video.ids")
 	if err := viper.UnmarshalKey("capture.video.pipelines", &s.VideoPipelines, viper.DecodeHook(
-		utils.JsonStringAutoDecode(s.VideoPipelines),
+		mapstructure.ComposeDecodeHookFunc(
+			utils.JsonStringAutoDecode(s.VideoPipelines),
+			videoPipelineShorthandHook(),
+		),
 	)); err != nil {
 		log.Warn().Err(err).Msgf("unable to parse video pipelines")
 	}

server/internal/config/capture_test.go

@@ -0,0 +1,58 @@
+package config
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/spf13/cobra"
+	"github.com/spf13/viper"
+)
+
+// loadCaptureFromEnv mirrors the production config flow: env prefix setup,
+// flag registration via Init, then value population via Set.
+func loadCaptureFromEnv(t *testing.T, pipelines string) *Capture {
+	t.Helper()
+
+	viper.Reset()
+	viper.SetEnvPrefix("NEKO")
+	viper.SetEnvKeyReplacer(strings.NewReplacer(".", "_"))
+	viper.AutomaticEnv()
+
+	t.Setenv("NEKO_CAPTURE_VIDEO_PIPELINES", pipelines)
+
+	c := &Capture{}
+	cmd := &cobra.Command{}
+	if err := c.Init(cmd); err != nil {
+		t.Fatal(err)
+	}
+	c.Set()
+	return c
+}
+
+func TestVideoPipelinesEnv(t *testing.T) {
+	const pipeline = "ximagesrc display-name={display} show-pointer=false ! appsink name=appsink"
+
+	t.Run("object entries with gst_pipeline keep working", func(t *testing.T) {
+		c := loadCaptureFromEnv(t, `{"high":{"gst_pipeline":"`+pipeline+`"}}`)
+
+		cfg, ok := c.VideoPipelines["high"]
+		if !ok {
+			t.Fatalf("pipeline entry missing, got %v", c.VideoPipelines)
+		}
+		if cfg.GstPipeline != pipeline {
+			t.Errorf("expected pipeline %q, got %q", pipeline, cfg.GstPipeline)
+		}
+	})
+
+	t.Run("bare pipeline string entries are accepted", func(t *testing.T) {
+		c := loadCaptureFromEnv(t, `{"high":"`+pipeline+`"}`)
+
+		cfg, ok := c.VideoPipelines["high"]
+		if !ok {
+			t.Fatalf("bare pipeline string entry was dropped and neko fell back to the default vp8 pipeline, got %v", c.VideoPipelines)
+		}
+		if cfg.GstPipeline != pipeline {
+			t.Errorf("expected pipeline %q, got %q", pipeline, cfg.GstPipeline)
+		}
+	})
+}