简化 context builder 的防御性兼容逻辑

internal/context/builder.go

@@ -8,21 +8,18 @@ import (
 type DefaultBuilder struct {
 	stablePromptSources  []promptSectionSource
 	dynamicPromptSources []promptSectionSource
-	promptSources        []promptSectionSource
 	trimPolicy           messageTrimPolicy
 }
 
 // newStablePromptSources 返回稳定提示词来源列表，适合作为缓存前缀。
-// extra 中的非 nil SectionSource 也会追加到 stable 中（如 memo 持久记忆索引）。
+// extra 会追加到 stable 中（如 memo 持久记忆索引）。
 func newStablePromptSources(extra ...SectionSource) []promptSectionSource {
 	sources := []promptSectionSource{
 		corePromptSource{},
 		newRulesPromptSource(nil),
 	}
 	for _, src := range extra {
-		if src != nil {
-			sources = append(sources, src)
-		}
+		sources = append(sources, src)
 	}
 	return sources
 }
@@ -41,7 +38,6 @@ func newDynamicPromptSources() []promptSectionSource {
 }
 
 // NewConfiguredBuilder 基于可选 SectionSource 列表构建上下文构建器，是推荐的统一构造入口。
-// sources 中 nil 元素会被跳过。
 func NewConfiguredBuilder(sources ...SectionSource) Builder {
 	return &DefaultBuilder{
 		stablePromptSources:  newStablePromptSources(sources...),
@@ -74,29 +70,17 @@ func (b *DefaultBuilder) Build(ctx context.Context, input BuildInput) (BuildResu
 		return BuildResult{}, err
 	}
 
-	stableSources := b.stablePromptSources
-	dynamicSources := b.dynamicPromptSources
-
-	// 兼容旧构造方式：如果新字段未设置但旧 promptSources 有内容，回退到旧单列表。
-	if len(stableSources) == 0 && len(dynamicSources) == 0 && len(b.promptSources) > 0 {
-		stableSources = b.promptSources
+	stableSections, err := collectPromptSections(ctx, input, b.stablePromptSources)
+	if err != nil {
+		return BuildResult{}, err
 	}
+	stablePrompt := composeSystemPrompt(stableSections...)
 
-	var stablePrompt, dynamicPrompt string
-	if stableSources != nil {
-		stableSections, err := collectPromptSections(ctx, input, stableSources)
-		if err != nil {
-			return BuildResult{}, err
-		}
-		stablePrompt = composeSystemPrompt(stableSections...)
-	}
-	if dynamicSources != nil {
-		dynamicSections, err := collectPromptSections(ctx, input, dynamicSources)
-		if err != nil {
-			return BuildResult{}, err
-		}
-		dynamicPrompt = composeSystemPrompt(dynamicSections...)
+	dynamicSections, err := collectPromptSections(ctx, input, b.dynamicPromptSources)
+	if err != nil {
+		return BuildResult{}, err
 	}
+	dynamicPrompt := composeSystemPrompt(dynamicSections...)
 
 	systemPrompt := joinSystemPromptParts(stablePrompt, dynamicPrompt)
 

internal/context/builder_test.go

@@ -263,10 +263,12 @@ func TestDefaultBuilderBuildPlacesRulesBeforeMemo(t *testing.T) {
 	}
 
 	builder := &DefaultBuilder{
-		promptSources: []promptSectionSource{
+		stablePromptSources: []promptSectionSource{
 			corePromptSource{},
 			newRulesPromptSource(rules.NewLoader(baseDir)),
 			stubPromptSectionSource{sections: []promptSection{{Title: "Memo", Content: "remember this"}}},
+		},
+		dynamicPromptSources: []promptSectionSource{
 			&systemStateSource{},
 		},
 	}
@@ -312,7 +314,7 @@ func TestDefaultBuilderBuildUsesSpanTrimPolicyWhenTrimPolicyIsUnset(t *testing.T
 	}
 
 	builder := &DefaultBuilder{
-		promptSources: []promptSectionSource{
+		stablePromptSources: []promptSectionSource{
 			stubPromptSectionSource{sections: []promptSection{{Title: "Stub", Content: "body"}}},
 		},
 	}
@@ -337,7 +339,7 @@ func TestDefaultBuilderBuildReturnsPromptSourceError(t *testing.T) {
 	t.Parallel()
 
 	builder := &DefaultBuilder{
-		promptSources: []promptSectionSource{
+		stablePromptSources: []promptSectionSource{
 			stubPromptSectionSource{err: fmt.Errorf("source failed")},
 		},
 	}
@@ -643,10 +645,12 @@ func TestNewConfiguredBuilder(t *testing.T) {
 		}
 	})
 
-	t.Run("nil section sources are skipped", func(t *testing.T) {
-		builder := NewConfiguredBuilder(nil, stubPromptSectionSource{
+	t.Run("multiple extra section sources are appended", func(t *testing.T) {
+		builder := NewConfiguredBuilder(stubPromptSectionSource{
+			sections: []promptSection{{Title: "First", Content: "first body"}},
+		}, stubPromptSectionSource{
 			sections: []promptSection{{Title: "Extra", Content: "extra body"}},
-		}, nil)
+		})
 		input := BuildInput{
 			Messages: []providertypes.Message{{Role: "user", Parts: []providertypes.ContentPart{providertypes.NewTextPart("hello")}}},
 			Metadata: testMetadata(t.TempDir()),
@@ -658,6 +662,9 @@ func TestNewConfiguredBuilder(t *testing.T) {
 		if !strings.Contains(result.SystemPrompt, "## Extra") {
 			t.Errorf("expected Extra section in system prompt")
 		}
+		if !strings.Contains(result.SystemPrompt, "## First") {
+			t.Errorf("expected First section in system prompt")
+		}
 	})
 }
 
@@ -895,23 +902,30 @@ func TestDefaultBuilderBuildMemoIsStable(t *testing.T) {
 	}
 }
 
-func TestDefaultBuilderBuildStableAndDynamicPreservesBackwardCompat(t *testing.T) {
+func TestDefaultBuilderBuildStableAndDynamicFields(t *testing.T) {
 	t.Parallel()
 
 	builder := &DefaultBuilder{
-		promptSources: []promptSectionSource{
-			stubPromptSectionSource{sections: []promptSection{{Title: "Old", Content: "old style"}}},
+		stablePromptSources: []promptSectionSource{
+			stubPromptSectionSource{sections: []promptSection{{Title: "Stable", Content: "stable style"}}},
 		},
+		dynamicPromptSources: []promptSectionSource{
+			stubPromptSectionSource{sections: []promptSection{{Title: "Dynamic", Content: "dynamic style"}}},
+		},
+		trimPolicy: spanMessageTrimPolicy{},
 	}
 
 	result, err := builder.Build(stdcontext.Background(), BuildInput{})
 	if err != nil {
 		t.Fatalf("Build() error = %v", err)
 	}
-	if !strings.Contains(result.SystemPrompt, "old style") {
-		t.Fatalf("expected old style content in system prompt, got %q", result.SystemPrompt)
+	if !strings.Contains(result.SystemPrompt, "stable style") || !strings.Contains(result.SystemPrompt, "dynamic style") {
+		t.Fatalf("expected stable and dynamic content in system prompt, got %q", result.SystemPrompt)
+	}
+	if !strings.Contains(result.StableSystemPrompt, "stable style") {
+		t.Fatalf("expected stable content in StableSystemPrompt, got %q", result.StableSystemPrompt)
 	}
-	if !strings.Contains(result.StableSystemPrompt, "old style") {
-		t.Fatalf("expected old style content in StableSystemPrompt, got %q", result.StableSystemPrompt)
+	if !strings.Contains(result.DynamicSystemPrompt, "dynamic style") {
+		t.Fatalf("expected dynamic content in DynamicSystemPrompt, got %q", result.DynamicSystemPrompt)
 	}
 }