feat(parser/plugin): new parser that can load from a plugin (#81)

internal/parser/all.go

@@ -10,6 +10,7 @@ import (
 	_ "github.com/joint-online-judge/JOJ3/internal/parser/healthcheck"
 	_ "github.com/joint-online-judge/JOJ3/internal/parser/keyword"
 	_ "github.com/joint-online-judge/JOJ3/internal/parser/log"
+	_ "github.com/joint-online-judge/JOJ3/internal/parser/plugin"
 	_ "github.com/joint-online-judge/JOJ3/internal/parser/resultdetail"
 	_ "github.com/joint-online-judge/JOJ3/internal/parser/resultstatus"
 	_ "github.com/joint-online-judge/JOJ3/internal/parser/sample"

internal/parser/plugin/meta.go

@@ -0,0 +1,21 @@
+// Package plugin provides functionality to load and run parser plugins
+// dynamically. It is used for custom parsers.
+// The plugin needs to be located at `ModPath` and export a symbol with name
+// `SymName` that implements the stage.Parser interface.
+
+package plugin
+
+import "github.com/joint-online-judge/JOJ3/internal/stage"
+
+var name = "plugin"
+
+type Conf struct {
+	ModPath string
+	SymName string `default:"Parser"`
+}
+
+type Plugin struct{}
+
+func init() {
+	stage.RegisterParser(name, &Plugin{})
+}

internal/parser/plugin/parser.go

@@ -0,0 +1,31 @@
+package plugin
+
+import (
+	"fmt"
+	"plugin"
+
+	"github.com/joint-online-judge/JOJ3/internal/stage"
+)
+
+func (*Plugin) Run(results []stage.ExecutorResult, confAny any) (
+	[]stage.ParserResult, bool, error,
+) {
+	conf, err := stage.DecodeConf[Conf](confAny)
+	if err != nil {
+		return nil, true, err
+	}
+	plug, err := plugin.Open(conf.ModPath)
+	if err != nil {
+		return nil, true, err
+	}
+	symParser, err := plug.Lookup(conf.SymName)
+	if err != nil {
+		return nil, true, err
+	}
+	var parser stage.Parser
+	parser, ok := symParser.(stage.Parser)
+	if !ok {
+		return nil, true, fmt.Errorf("unexpected type from module symbol")
+	}
+	return parser.Run(results, confAny)
+}