fix: exclude DiffSource interface field from JSON serialization (#305) by tianzhou · Pull Request #309 · pgplex/pgschema

tianzhou · 2026-02-22T03:38:43Z

Summary

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 via pgschema apply --plan plan.json.
Changed the JSON tag on Diff.Source from json:"source,omitempty" to json:"-" to exclude it from serialization. All in-memory usage (rewrite logic, display formatting) is unaffected.

Fixes #305

Test plan

New test TestPlanDebugJSONRoundTrip verifies debug JSON round-trip: serialize with ToJSONWithDebug(true) then deserialize with FromJSON()
Run: go test -v ./internal/plan -run TestPlanDebugJSONRoundTrip
All existing plan tests pass: go test -v ./internal/plan
Full CI suite passes

🤖 Generated with Claude Code

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Pull request overview

Fixes debug-mode plan JSON round-tripping by preventing an interface-typed field (diff.Diff.Source / DiffSource) from being serialized, which previously made plan.FromJSON() fail when applying --debug plans.

Changes:

Exclude diff.Diff.Source from JSON serialization/deserialization via json:"-".
Add a regression test that serializes a debug plan with ToJSONWithDebug(true) and verifies FromJSON() can load it successfully.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
`internal/diff/diff.go`	Stops serializing the interface-typed `Diff.Source` field to keep debug JSON loadable.
`internal/plan/plan_test.go`	Adds a debug JSON round-trip test covering issue #305.

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Copilot · 2026-02-22T03:41:19Z

internal/diff/diff.go

 	Operation  DiffOperation  `json:"operation"` // create, alter, drop, replace
 	Path       string         `json:"path"`
-	Source     DiffSource     `json:"source,omitempty"`
+	Source     DiffSource     `json:"-"`


Diff.Source is now excluded from JSON, but the code doesn’t explain why. Consider adding a short inline comment on this field noting that it’s an interface (DiffSource) and is intentionally not serializable/deserializable (issue #305), to reduce the chance of an accidental revert later.

Suggested change

Source DiffSource `json:"-"`

Source DiffSource `json:"-"` // interface field; intentionally not JSON-serializable/deserializable (see issue #305)

Added inline comment: // interface; not JSON-serializable (see #305)

Copilot · 2026-02-22T03:41:19Z

internal/plan/plan_test.go

+	loaded, err := FromJSON([]byte(debugJSON))
+	if err != nil {
+		t.Fatalf("Failed to deserialize debug plan JSON: %v", err)
+	}
+


Optional: consider asserting that debug mode actually emitted source_diffs (e.g., len(loaded.SourceDiffs) > 0). It makes the test more robust by ensuring ToJSONWithDebug(true) continues to include debug diffs, rather than the test passing if that output changes later.

Added len(loaded.SourceDiffs) == 0 assertion to verify debug mode actually emits SourceDiffs.

Copilot · 2026-02-22T03:41:19Z

internal/plan/plan_test.go

+
+	p := NewPlan(diffs)
+
+	// Serialize with debug mode (includes SourceDiffs with Source interface fields)


The comment says debug serialization "includes SourceDiffs with Source interface fields", but with Diff.Source tagged json:"-" the Source field won’t be present in the JSON anymore. Updating the comment to reflect the new behavior will prevent confusion when debugging future failures.

Suggested change

// Serialize with debug mode (includes SourceDiffs with Source interface fields)

// Serialize with debug mode (includes additional debug metadata but omits Diff.Source interface fields)

Fixed. Comment now reads: // includes SourceDiffs; Diff.Source is excluded via json:"-"

greptile-apps · 2026-02-22T03:41:29Z

Greptile Summary

Fixed JSON serialization issue where --debug plans couldn't be deserialized by FromJSON(). The Diff.Source field (a DiffSource interface) is now excluded from JSON output via json:"-" tag, since Go's json.Unmarshal cannot reconstruct interface types. This field is only used in-memory for rewrite logic and display formatting, not needed for plan persistence.

Key Changes:

Changed Diff.Source JSON tag to exclude field from serialization
Added comprehensive test verifying debug JSON round-trip works correctly
All in-memory usage patterns (rewrite logic in plan/rewrite.go, display formatting) remain unaffected since they operate on freshly-generated plans before serialization

Confidence Score: 5/5

This PR is safe to merge with minimal risk
The fix is minimal, well-targeted, and addresses the root cause directly. The Source field is only used in-memory during plan generation (rewrite logic and display), never after JSON deserialization. The comprehensive test verifies the fix works and prevents regression. All existing usages of Source field are in plan generation code paths, not in the apply-from-JSON code path.
No files require special attention

Important Files Changed

Filename	Overview
internal/diff/diff.go	Changed `Source` field JSON tag from `json:"source,omitempty"` to `json:"-"` to exclude it from serialization, fixing JSON round-trip issue
internal/plan/plan_test.go	Added comprehensive test `TestPlanDebugJSONRoundTrip` verifying debug JSON serialization/deserialization and round-trip stability

_{Last reviewed commit: 76db096}

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>

Copilot AI review requested due to automatic review settings February 22, 2026 03:38

Copilot started reviewing on behalf of tianzhou February 22, 2026 03:39 View session

Copilot AI reviewed Feb 22, 2026

View reviewed changes

tianzhou force-pushed the fix/issue-305-debug-json-deserialization branch from 76db096 to 6c6fb5d Compare February 22, 2026 03:43

tianzhou merged commit 2cfa5e5 into main Feb 22, 2026
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fix: exclude DiffSource interface field from JSON serialization (#305)#309

fix: exclude DiffSource interface field from JSON serialization (#305)#309
tianzhou merged 1 commit intomainfrom
fix/issue-305-debug-json-deserialization

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	Source DiffSource `json:"-"`
	Source DiffSource `json:"-"` // interface field; intentionally not JSON-serializable/deserializable (see issue #305)


		p := NewPlan(diffs)

		// Serialize with debug mode (includes SourceDiffs with Source interface fields)

	// Serialize with debug mode (includes SourceDiffs with Source interface fields)
	// Serialize with debug mode (includes additional debug metadata but omits Diff.Source interface fields)

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tianzhou commented Feb 22, 2026

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greptile-apps bot commented Feb 22, 2026

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Confidence Score: 5/5

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