From 6c6fb5d3d2f8bfef5c5bac30f370646a6ff5f73a Mon Sep 17 00:00:00 2001
From: Tianzhou <t@bytebase.com>
Date: Sat, 21 Feb 2026 19:38:27 -0800
Subject: [PATCH] fix: exclude DiffSource interface field from JSON
 serialization (#305)

Plans generated with --debug included the Diff.Source field (a DiffSource
interface) in JSON output. Go's json.Unmarshal cannot reconstruct interface
types, causing FromJSON() to fail when applying debug plans.

Change the JSON tag from `json:"source,omitempty"` to `json:"-"` to exclude
Source from serialization. All in-memory usage (rewrite, formatting, display)
is unaffected.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
---
 internal/diff/diff.go      |  2 +-
 internal/plan/plan_test.go | 61 ++++++++++++++++++++++++++++++++++++++
 2 files changed, 62 insertions(+), 1 deletion(-)

diff --git a/internal/diff/diff.go b/internal/diff/diff.go
index aad14c69..bb872b79 100644
--- a/internal/diff/diff.go
+++ b/internal/diff/diff.go
@@ -251,7 +251,7 @@ type Diff struct {
 	Type       DiffType       `json:"type"`
 	Operation  DiffOperation  `json:"operation"` // create, alter, drop, replace
 	Path       string         `json:"path"`
-	Source     DiffSource     `json:"source,omitempty"`
+	Source     DiffSource     `json:"-"` // interface; not JSON-serializable (see #305)
 }
 
 type ddlDiff struct {
diff --git a/internal/plan/plan_test.go b/internal/plan/plan_test.go
index 7b70161f..76803ea5 100644
--- a/internal/plan/plan_test.go
+++ b/internal/plan/plan_test.go
@@ -260,3 +260,64 @@ func TestPlanJSONLoadedSummary(t *testing.T) {
 		t.Error("Summary should not say \"No changes detected\" when there are changes")
 	}
 }
+
+func TestPlanDebugJSONRoundTrip(t *testing.T) {
+	// Issue #305: Plans generated with --debug produce JSON that cannot be
+	// deserialized by FromJSON() because the Diff.Source field is a Go interface
+	// (DiffSource) that json.Unmarshal cannot reconstruct.
+	oldSQL := `CREATE TABLE users (
+		id integer NOT NULL
+	);`
+
+	newSQL := `CREATE TABLE users (
+		id integer NOT NULL,
+		name text NOT NULL
+	);
+	CREATE TABLE posts (
+		id integer NOT NULL,
+		title text NOT NULL
+	);`
+
+	oldIR := parseSQL(t, oldSQL)
+	newIR := parseSQL(t, newSQL)
+	diffs := diff.GenerateMigration(oldIR, newIR, "public")
+
+	p := NewPlan(diffs)
+
+	// Serialize with debug mode (includes SourceDiffs; Diff.Source is excluded via json:"-")
+	debugJSON, err := p.ToJSONWithDebug(true)
+	if err != nil {
+		t.Fatalf("Failed to serialize plan with debug: %v", err)
+	}
+
+	// Deserialize - this should succeed
+	loaded, err := FromJSON([]byte(debugJSON))
+	if err != nil {
+		t.Fatalf("Failed to deserialize debug plan JSON: %v", err)
+	}
+
+	// Verify debug mode actually included SourceDiffs
+	if len(loaded.SourceDiffs) == 0 {
+		t.Error("Debug plan should include SourceDiffs")
+	}
+
+	// Verify the loaded plan has valid groups and steps
+	if len(loaded.Groups) == 0 {
+		t.Error("Loaded plan should have at least one execution group")
+	}
+
+	// Re-serialize without debug and verify round-trip stability
+	normalJSON, err := loaded.ToJSON()
+	if err != nil {
+		t.Fatalf("Failed to re-serialize loaded plan: %v", err)
+	}
+
+	loaded2, err := FromJSON([]byte(normalJSON))
+	if err != nil {
+		t.Fatalf("Failed to deserialize re-serialized plan: %v", err)
+	}
+
+	if len(loaded2.Groups) != len(loaded.Groups) {
+		t.Errorf("Group count mismatch: got %d, want %d", len(loaded2.Groups), len(loaded.Groups))
+	}
+}