feat(config): inherit assignment configuration via extends

config/assignment.go

@@ -27,6 +27,10 @@ func GetAssignmentConfig(course, assignment string, onlyForStudentsOrGroups ...s
 			Msg("configuration for assignment not found")
 	}
 
+	// Resolve `extends` inheritance before reading any fields so the rest of
+	// the config loading sees the merged, effective configuration.
+	resolveAssignmentInheritance(course, assignment)
+
 	assignmentKey := course + "." + assignment
 	per := per(assignmentKey)
 

config/inheritance.go

@@ -0,0 +1,119 @@
+package config
+
+import (
+	"fmt"
+	"strings"
+
+	"github.com/rs/zerolog/log"
+	"github.com/spf13/viper"
+)
+
+// inheritKey is the assignment config field used to inherit configuration from
+// another assignment within the same course (OOP-style single inheritance).
+//
+//	blatt10:
+//	  extends: blatt09     # inherit everything from blatt09 ...
+//	  assignmentpath: blatt-10   # ... and override only what differs
+const inheritKey = "extends"
+
+// resolveAssignmentInheritance resolves the `extends` chain for the given
+// assignment and writes the merged, effective configuration back into viper at
+// the assignment key. After this call the rest of the config loading reads the
+// inherited values transparently via the usual viper.Get* calls.
+//
+// Inheritance semantics (child overrides parent):
+//   - maps (e.g. mergeRequest, startercode, deferredBranches) are deep-merged,
+//     so a child can override a single nested field while keeping the rest;
+//   - scalars and slices (e.g. branches, issueNumbers) are replaced wholesale.
+//
+// Parents may themselves extend other assignments; chains are resolved
+// recursively. Cycles and missing parents are fatal.
+func resolveAssignmentInheritance(course, assignment string) {
+	assignmentKey := course + "." + assignment
+	if !viper.IsSet(assignmentKey + "." + inheritKey) {
+		return
+	}
+
+	merged := mergedAssignmentMap(course, assignment, map[string]bool{})
+	delete(merged, inheritKey)
+	viper.Set(assignmentKey, merged)
+}
+
+// mergedAssignmentMap returns the assignment's configuration map with all parent
+// configuration (via `extends`) merged in. The child's own values win.
+func mergedAssignmentMap(course, assignment string, seen map[string]bool) map[string]any {
+	if seen[assignment] {
+		log.Fatal().
+			Str("course", course).
+			Str("assignment", assignment).
+			Msg("cyclic 'extends' inheritance detected in assignment configuration")
+	}
+	seen[assignment] = true
+
+	own := viper.GetStringMap(course + "." + assignment)
+
+	parentRaw, ok := own[inheritKey]
+	if !ok {
+		return own
+	}
+
+	parent, ok := parentRaw.(string)
+	if !ok || strings.TrimSpace(parent) == "" {
+		log.Fatal().
+			Str("course", course).
+			Str("assignment", assignment).
+			Msg("'extends' must be the name of another assignment in the same course")
+	}
+	parent = strings.TrimSpace(parent)
+
+	if !viper.IsSet(course + "." + parent) {
+		log.Fatal().
+			Str("course", course).
+			Str("assignment", assignment).
+			Str("extends", parent).
+			Msg("assignment referenced by 'extends' not found")
+	}
+
+	parentMap := mergedAssignmentMap(course, parent, seen)
+
+	return deepMerge(parentMap, own)
+}
+
+// deepMerge returns a new map with child merged onto parent. Nested maps are
+// merged recursively; all other values (scalars, slices) are replaced by the
+// child's value.
+func deepMerge(parent, child map[string]any) map[string]any {
+	out := make(map[string]any, len(parent)+len(child))
+	for k, v := range parent {
+		out[k] = v
+	}
+	for k, childVal := range child {
+		if parentVal, ok := out[k]; ok {
+			parentMap, parentIsMap := asStringMap(parentVal)
+			childMap, childIsMap := asStringMap(childVal)
+			if parentIsMap && childIsMap {
+				out[k] = deepMerge(parentMap, childMap)
+				continue
+			}
+		}
+		out[k] = childVal
+	}
+	return out
+}
+
+// asStringMap normalizes the YAML/viper map representations (map[string]any or
+// map[any]any) into map[string]any, reporting whether the value was a map.
+func asStringMap(v any) (map[string]any, bool) {
+	switch m := v.(type) {
+	case map[string]any:
+		return m, true
+	case map[any]any:
+		out := make(map[string]any, len(m))
+		for k, val := range m {
+			out[fmt.Sprint(k)] = val
+		}
+		return out, true
+	default:
+		return nil, false
+	}
+}

config/inheritance_test.go

@@ -0,0 +1,214 @@
+package config
+
+import (
+	"testing"
+
+	"github.com/spf13/viper"
+)
+
+// baseAssignment sets up a fully-featured parent assignment ("blatt09") that
+// children inherit from.
+func baseAssignment(t *testing.T) {
+	t.Helper()
+	resetViper(t)
+
+	viper.Set("gitlab.host", "https://gitlab.example.org")
+	viper.Set("mpd", true)
+	viper.Set("mpd.coursepath", "mpd")
+	viper.Set("mpd.semesterpath", "ss26")
+	viper.Set("mpd.useCoursenameAsPrefix", true)
+	viper.Set("mpd.students", []string{"alice"})
+
+	viper.Set("mpd.blatt09", true)
+	viper.Set("mpd.blatt09.assignmentpath", "blatt-09")
+	viper.Set("mpd.blatt09.description", "Blatt 9")
+	viper.Set("mpd.blatt09.per", "student")
+	viper.Set("mpd.blatt09.mergeRequest", map[string]any{
+		"mergeMethod":  "semi_linear",
+		"squashOption": "never",
+		"pipeline":     true,
+	})
+	viper.Set("mpd.blatt09.startercode", map[string]any{
+		"url":        "git@gitlab.lrz.de:mpd/labs/blatt-09.git",
+		"fromBranch": "startercode",
+		"template":   true,
+	})
+	viper.Set("mpd.blatt09.branches", []map[string]any{
+		{"name": "main", "mergeOnly": true},
+	})
+	viper.Set("mpd.blatt09.deferredBranches", map[string]any{
+		"devcontainer": map[string]any{
+			"url":        "git@gitlab.lrz.de:mpd/devcontainer.git",
+			"fromBranch": "main",
+			"toBranch":   "devcontainer",
+		},
+		"solution": map[string]any{
+			"fromBranch":    "solution",
+			"orphan":        true,
+			"orphanMessage": "Lösung 9",
+		},
+	})
+}
+
+func TestInheritance_OverridesAndInherits(t *testing.T) {
+	baseAssignment(t)
+
+	// blatt10 extends blatt09 and only overrides what differs.
+	viper.Set("mpd.blatt10", true)
+	viper.Set("mpd.blatt10.extends", "blatt09")
+	viper.Set("mpd.blatt10.assignmentpath", "blatt-10")
+	viper.Set("mpd.blatt10.description", "Blatt 10")
+	// override only one nested field of startercode
+	viper.Set("mpd.blatt10.startercode", map[string]any{
+		"url": "git@gitlab.lrz.de:mpd/labs/blatt-10.git",
+	})
+
+	cfg := GetAssignmentConfig("mpd", "blatt10")
+
+	// overridden scalars
+	if cfg.Path != "mpd/ss26/blatt-10" {
+		t.Fatalf("Path = %q, want mpd/ss26/blatt-10", cfg.Path)
+	}
+	if cfg.Description != "Blatt 10" {
+		t.Fatalf("Description = %q, want Blatt 10", cfg.Description)
+	}
+
+	// inherited mergeRequest
+	if cfg.MergeRequest == nil || cfg.MergeRequest.MergeMethod != SemiLinearHistory {
+		t.Fatalf("MergeRequest = %#v, want inherited semi_linear", cfg.MergeRequest)
+	}
+	if !cfg.MergeRequest.PipelineMustSucceed {
+		t.Fatal("PipelineMustSucceed should be inherited as true")
+	}
+
+	// startercode: url overridden, rest deep-merged from parent
+	if cfg.Startercode == nil {
+		t.Fatal("Startercode should not be nil")
+	}
+	if cfg.Startercode.URL != "git@gitlab.lrz.de:mpd/labs/blatt-10.git" {
+		t.Fatalf("Startercode.URL = %q, want overridden blatt-10 url", cfg.Startercode.URL)
+	}
+	if cfg.Startercode.FromBranch != "startercode" {
+		t.Fatalf("Startercode.FromBranch = %q, want inherited 'startercode'", cfg.Startercode.FromBranch)
+	}
+	if !cfg.Startercode.Template {
+		t.Fatal("Startercode.Template should be inherited as true")
+	}
+
+	// deferredBranches inherited
+	if len(cfg.DeferredBranches) != 2 {
+		t.Fatalf("DeferredBranches len = %d, want 2", len(cfg.DeferredBranches))
+	}
+	if db, ok := cfg.DeferredBranches["solution"]; !ok || db.OrphanMessage != "Lösung 9" {
+		t.Fatalf("inherited solution deferred branch = %#v", db)
+	}
+
+	// branches inherited
+	if len(cfg.Branches) != 1 || cfg.Branches[0].Name != "main" || !cfg.Branches[0].MergeOnly {
+		t.Fatalf("Branches = %#v, want inherited [main mergeOnly]", cfg.Branches)
+	}
+}
+
+func TestInheritance_DeepMergeNestedDeferredBranch(t *testing.T) {
+	baseAssignment(t)
+
+	viper.Set("mpd.blatt10", true)
+	viper.Set("mpd.blatt10.extends", "blatt09")
+	viper.Set("mpd.blatt10.assignmentpath", "blatt-10")
+	// override only the orphanMessage of the inherited "solution" deferred branch
+	viper.Set("mpd.blatt10.deferredBranches", map[string]any{
+		"solution": map[string]any{
+			"orphanMessage": "Lösung 10",
+		},
+	})
+
+	cfg := GetAssignmentConfig("mpd", "blatt10")
+
+	if len(cfg.DeferredBranches) != 2 {
+		t.Fatalf("DeferredBranches len = %d, want 2 (devcontainer kept)", len(cfg.DeferredBranches))
+	}
+	sol, ok := cfg.DeferredBranches["solution"]
+	if !ok {
+		t.Fatal("solution deferred branch missing")
+	}
+	if sol.OrphanMessage != "Lösung 10" {
+		t.Fatalf("solution.OrphanMessage = %q, want overridden 'Lösung 10'", sol.OrphanMessage)
+	}
+	if sol.FromBranch != "solution" {
+		t.Fatalf("solution.FromBranch = %q, want inherited 'solution'", sol.FromBranch)
+	}
+	if _, ok := cfg.DeferredBranches["devcontainer"]; !ok {
+		t.Fatal("devcontainer deferred branch should be inherited")
+	}
+}
+
+func TestInheritance_MultiLevelChain(t *testing.T) {
+	baseAssignment(t)
+
+	viper.Set("mpd.blatt10", true)
+	viper.Set("mpd.blatt10.extends", "blatt09")
+	viper.Set("mpd.blatt10.assignmentpath", "blatt-10")
+
+	viper.Set("mpd.blatt11", true)
+	viper.Set("mpd.blatt11.extends", "blatt10")
+	viper.Set("mpd.blatt11.assignmentpath", "blatt-11")
+
+	cfg := GetAssignmentConfig("mpd", "blatt11")
+
+	if cfg.Path != "mpd/ss26/blatt-11" {
+		t.Fatalf("Path = %q, want mpd/ss26/blatt-11", cfg.Path)
+	}
+	// inherited transitively from blatt09 via blatt10
+	if cfg.MergeRequest == nil || cfg.MergeRequest.MergeMethod != SemiLinearHistory {
+		t.Fatalf("MergeRequest = %#v, want transitively inherited semi_linear", cfg.MergeRequest)
+	}
+	if cfg.Startercode == nil || cfg.Startercode.FromBranch != "startercode" {
+		t.Fatalf("Startercode = %#v, want transitively inherited", cfg.Startercode)
+	}
+}
+
+func TestInheritance_NoExtendsIsUnaffected(t *testing.T) {
+	baseAssignment(t)
+
+	cfg := GetAssignmentConfig("mpd", "blatt09")
+
+	if cfg.Path != "mpd/ss26/blatt-09" {
+		t.Fatalf("Path = %q", cfg.Path)
+	}
+	if cfg.Startercode == nil || cfg.Startercode.URL != "git@gitlab.lrz.de:mpd/labs/blatt-09.git" {
+		t.Fatalf("Startercode = %#v", cfg.Startercode)
+	}
+}
+
+func TestDeepMerge(t *testing.T) {
+	parent := map[string]any{
+		"a": 1,
+		"b": map[string]any{"x": 1, "y": 2},
+		"c": []string{"keep"},
+	}
+	child := map[string]any{
+		"b": map[string]any{"y": 20, "z": 30},
+		"c": []string{"replaced"},
+		"d": 4,
+	}
+
+	got := deepMerge(parent, child)
+
+	if got["a"] != 1 {
+		t.Fatalf("a = %v, want inherited 1", got["a"])
+	}
+	if got["d"] != 4 {
+		t.Fatalf("d = %v, want 4", got["d"])
+	}
+	bm, ok := asStringMap(got["b"])
+	if !ok {
+		t.Fatalf("b is not a map: %#v", got["b"])
+	}
+	if bm["x"] != 1 || bm["y"] != 20 || bm["z"] != 30 {
+		t.Fatalf("merged b = %#v, want {x:1 y:20 z:30}", bm)
+	}
+	cs, ok := got["c"].([]string)
+	if !ok || len(cs) != 1 || cs[0] != "replaced" {
+		t.Fatalf("c = %#v, want slice replaced wholesale", got["c"])
+	}
+}