Add migration system coverage tests (550+ tests) by Godzilla675 · Pull Request #997 · zio/zio-blocks

Godzilla675 · 2026-02-06T18:09:00Z

Adds comprehensive test coverage for the schema migration system to meet the 80% branch coverage minimum.

Changes

9 new test files with 550+ tests covering all migration system components
Fixed .scalafmt.conf with scala213 dialect override for Scala 2 files
Tests cover: MigrationSchemas, DynamicSchemaExpr, MigrationValidator, DynamicMigration, MigrationBuilder, MigrationAction, MigrationError, Selector, Migration

Replaces #984 (closed while CI was still running)

…structure comparison - Add validatePath/validatePathRecursive to check Wrap path segments match schema structure - Validate Elements only on sequences, MapKeys/MapValues only on maps, Case only on variants - Add lenient structure comparison mode when structural migration actions are present - Handle Split/Join/Mandate/Optionalize by relaxing field presence checks - Preserve optionality checking for Dynamic fields even in lenient mode - Fix error message format for optionality and structure mismatches Fixes 13 failing MigrationValidatorSpec tests and 1 MigrationValidatorOptionalitySpec test.

…for branch gap

… coverage

Add 70+ tests targeting specific uncovered branches: - DynamicSchemaExpr: Path/DefaultValue/ResolvedDefault/Literal eval - DynamicSchemaExpr: coercePrimitive identity + cross-type conversions - DynamicSchemaExpr: evalPrimitiveArithmetic all type combos - MigrationValidator: compareStructures all match arms - MigrationValidator: validatePathRecursive all node error paths - MigrationValidator: Join/Split path-must-end-in-field errors

Copilot

Pull request overview

Adds a new schema migration subsystem to zio.blocks.schema (typed Migration wrapping a serializable DynamicMigration + MigrationAction + DynamicSchemaExpr), plus extensive test coverage and documentation updates to meet branch coverage targets.

Changes:

Introduces the migration core APIs (Migration, DynamicMigration, MigrationAction, DynamicSchemaExpr, MigrationBuilder, Selector) and Scala 2/3 selector-macro syntax.
Adds ~550 tests across migration components, plus Scala 3-only structural-schema tests.
Updates docs/examples and test helpers (newline normalization), and adjusts scalafmt dialect overrides.

Reviewed changes

Copilot reviewed 48 out of 48 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
schema/shared/src/test/scala/zio/blocks/schema/migration/SelectorMacrosSpec.scala	Tests Scala selector-macro path extraction to `DynamicOptic`.
schema/shared/src/test/scala/zio/blocks/schema/migration/SelectorCoverageSpec.scala	Coverage tests for `Selector` composition and `toOptic`.
schema/shared/src/test/scala/zio/blocks/schema/migration/MigrationValidatorOptionalitySpec.scala	Regression test for optionality mismatch validation.
schema/shared/src/test/scala/zio/blocks/schema/migration/MigrationValidatorCoverageSpec.scala	Broad branch coverage for `MigrationValidator` logic.
schema/shared/src/test/scala/zio/blocks/schema/migration/MigrationSpec.scala	Tests typed `Migration` behavior (apply/applyDynamic/composition/reverse).
schema/shared/src/test/scala/zio/blocks/schema/migration/MigrationSchemasSerializationSpec.scala	Validates JSON codec round-trip for `DynamicMigration`.
schema/shared/src/test/scala/zio/blocks/schema/migration/MigrationSchemasCoverageSpec.scala	Round-trip tests for schemas of migration ADTs.
schema/shared/src/test/scala/zio/blocks/schema/migration/MigrationErrorSpec.scala	Tests `MigrationError` messages and composition.
schema/shared/src/test/scala/zio/blocks/schema/migration/MigrationErrorCoverageSpec.scala	Coverage tests for all `MigrationError` variants.
schema/shared/src/test/scala/zio/blocks/schema/migration/MigrationCoverageSpec.scala	Coverage tests for `Migration` helpers and composition.
schema/shared/src/test/scala/zio/blocks/schema/migration/MigrationBuilderSpec.scala	High-level usage tests for `MigrationBuilder`.
schema/shared/src/test/scala/zio/blocks/schema/migration/MigrationBuilderCoverageSpec.scala	Coverage tests for `MigrationBuilder` API + helpers.
schema/shared/src/test/scala/zio/blocks/schema/migration/MigrationActionSpec.scala	Tests action reversibility semantics.
schema/shared/src/test/scala/zio/blocks/schema/migration/MigrationActionCoverageSpec.scala	Coverage tests for `MigrationAction.reverse` across variants.
schema/shared/src/test/scala/zio/blocks/schema/migration/DynamicSchemaExprSpec.scala	Tests `DynamicSchemaExpr.eval` for many operators.
schema/shared/src/test/scala/zio/blocks/schema/migration/DynamicSchemaExprSerializationSpec.scala	Serialization round-trip tests for `DynamicSchemaExpr`.
schema/shared/src/test/scala/zio/blocks/schema/migration/DefaultValueResolutionSpec.scala	Tests build-time `DefaultValue` resolution behavior.
schema/shared/src/test/scala/zio/blocks/schema/json/JsonTestUtils.scala	Normalizes newlines for JSON golden-string assertions.
schema/shared/src/test/scala-3/zio/blocks/schema/migration/StructuralMigrationApplySpec.scala	Scala 3-only tests for structural schemas and typed apply erroring.
schema/shared/src/main/scala/zio/blocks/schema/migration/package.scala	Adds migration package object scaladoc entry point.
schema/shared/src/main/scala/zio/blocks/schema/migration/Selector.scala	Adds `Selector` abstraction for typed path composition.
schema/shared/src/main/scala/zio/blocks/schema/migration/MigrationError.scala	Adds migration error model with path-aware messages.
schema/shared/src/main/scala/zio/blocks/schema/migration/MigrationBuilder.scala	Adds fluent builder + build validation + default resolution.
schema/shared/src/main/scala/zio/blocks/schema/migration/MigrationAction.scala	Defines migration action algebra + `reverse`.
schema/shared/src/main/scala/zio/blocks/schema/migration/Migration.scala	Adds typed migration wrapper + composition + reverse.
schema/shared/src/main/scala/zio/blocks/schema/migration/DynamicSchemaExpr.scala	Adds serializable expression language for transforms.
schema/shared/src/main/scala/zio/blocks/schema/migration/DynamicMigration.scala	Adds action interpreter over `DynamicValue`.
schema/shared/src/main/scala/zio/blocks/schema/json/JsonBinaryCodecDeriver.scala	Fixes delayed `usedRegisters` init for recursive records in codecs.
schema/shared/src/main/scala/zio/blocks/schema/binding/Matcher.scala	Adds `StructuralMatcher` for structural types.
schema/shared/src/main/scala/zio/blocks/schema/binding/Deconstructor.scala	Adds `StructuralDeconstructor` marker/abstraction.
schema/shared/src/main/scala/zio/blocks/schema/binding/Constructor.scala	Adds `StructuralConstructor` marker/abstraction.
schema/shared/src/main/scala-3/zio/blocks/schema/migration/SelectorMacros.scala	Scala 3 macro implementation for selector lambdas to `DynamicOptic`.
schema/shared/src/main/scala-3/zio/blocks/schema/migration/MigrationBuilderSyntax.scala	Scala 3 inline extension syntax for selector-based builder ops.
schema/shared/src/main/scala-3/zio/blocks/schema/SchemaCompanionVersionSpecific.scala	Adds Scala 3 `Schema.structural` derivation for refinement/union types.
schema/shared/src/main/scala-2/zio/blocks/schema/migration/SelectorMacros.scala	Scala 2 macro implementation for selector lambdas to `DynamicOptic`.
schema/shared/src/main/scala-2/zio/blocks/schema/migration/MigrationBuilderSyntax.scala	Scala 2 macro-based syntax for selector-based builder ops.
schema/shared/src/main/scala-2/zio/blocks/schema/SchemaCompanionVersionSpecific.scala	Adds Scala 2 stub macro for `Schema.structural` (Scala 3-only feature).
schema-toon/src/test/scala/zio/blocks/schema/toon/ToonTestUtils.scala	Normalizes newlines for Toon golden-string assertions.
docs/reference/validation.md	Updates examples to use `Chunk` instead of `Vector` for `DynamicValue` constructors.
docs/reference/schema.md	Updates `DynamicValue` examples to use `Chunk`.
docs/reference/migration.md	Adds migration system reference documentation.
.scalafmt.conf	Overrides scala213 dialect for `scala-2` sources.

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Copilot · 2026-02-06T18:16:50Z

docs/reference/migration.md

+```scala
+Migration
+  .newBuilder[OldType, NewType]
+  // Record operations
+  .addField(path, defaultExpr)
+  .dropField(path, defaultForReverse)
+  .renameField(fromPath, toPath)
+  .transformField(path, transform, reverseTransform)
+  .mandateField(path, default)
+  .optionalizeField(path)
+  .changeType(path, converter, reverseConverter)
+  .joinFields(targetPath, sourcePaths, combiner, splitter)
+  .splitField(sourcePath, targetPaths, splitter, combiner)
+  // Enum operations
+  .renameCase(path, from, to)
+  .transformCase(path, caseName, nestedActions)
+  // Collection operations
+  .transformElements(path, transform, reverseTransform)
+  .transformKeys(path, transform, reverseTransform)
+  .transformValues(path, transform, reverseTransform)


The MigrationBuilder API snippet lists methods that don't match the actual builder surface (e.g. .changeType vs MigrationBuilder.changeFieldType, and .renameCase(path, ...) / .transformCase(path, ...) vs renameCaseAt / transformCaseAt). Updating these names in the docs will prevent copy/paste examples from failing to compile.

Copilot · 2026-02-06T18:16:51Z

schema/shared/src/main/scala/zio/blocks/schema/migration/DynamicMigration.scala

+      modifyAtPathWithParentContext(value, at) { (_, targetValue) =>
+        transform.eval(targetValue).left.map(wrapExprError(at, "TransformValue"))


TransformValue evaluates the expression on the field value (targetValue). That makes common transforms like Arithmetic(Path(root.field("age")), ...) fail because Path expects a record/parent context (similar to how AddField/Mandate/ChangeType evaluate against the surrounding context). Consider evaluating transform against the parent context from modifyAtPathWithParentContext (and then writing the resulting value back at at).

Suggested change

modifyAtPathWithParentContext(value, at) { (_, targetValue) =>

transform.eval(targetValue).left.map(wrapExprError(at, "TransformValue"))

modifyAtPathWithParentContext(value, at) { (context, _) =>

transform.eval(context).left.map(wrapExprError(at, "TransformValue"))

Copilot · 2026-02-06T18:16:51Z

schema/shared/src/main/scala/zio/blocks/schema/migration/DynamicMigration.scala

+    case MigrationAction.Mandate(at, default) =>
+      modifyAtPathWithParentContext(value, at) { (context, targetValue) =>
+        targetValue match {
+          case DynamicValue.Variant("None", _) =>
+            default.eval(context).left.map(wrapExprError(at, "Mandate"))
+          case DynamicValue.Variant("Some", inner) =>
+            Right(inner)
+          case other =>
+            // Already a non-optional value, return as-is
+            Right(other)
+        }
+      }
+
+    case MigrationAction.Optionalize(at, _) =>
+      modifyAtPath(value, at) { targetValue =>
+        // Wrap the value in a Some variant
+        Right(DynamicValue.Variant("Some", targetValue))
+      }


Mandate/Optionalize currently treat Option payloads as Variant("Some", <value>), but the schema representation for Some is a record wrapper (Variant("Some", Record("value" -> ...)); see Reflect.some* in schema/shared/src/main/scala/zio/blocks/schema/Reflect.scala). As-is, optionality migrations will not round-trip through Schema.fromDynamicValue for real Option fields. Update Optionalize to wrap in a Record(Chunk("value" -> targetValue)) and update Mandate to unwrap that record (and handle missing/invalid shapes as errors).

Copilot · 2026-02-06T18:16:51Z

schema/shared/src/main/scala/zio/blocks/schema/migration/Selector.scala

+   * Create a selector for sequence elements.
+   */
+  def elements[A, B]: Selector[Seq[A], B] = Elements()
+


elements is typed as Selector[Seq[A], B] / Elements[A, B], which allows nonsensical selectors like Selector.elements[Int, String] even though element selection should preserve the element type. Consider changing this to def elements[A]: Selector[Seq[A], A] (and final case class Elements[A] extends Selector[Seq[A], A]) to keep the selector API genuinely type-safe.

Copilot · 2026-02-06T18:16:52Z

schema/shared/src/main/scala-2/zio/blocks/schema/migration/MigrationBuilderSyntax.scala

+    def dropField[T](selector: A => T): MigrationBuilder[A, B] =
+      macro MigrationBuilderSyntaxImpl.dropFieldImpl[A, B, T]
+
+    /**


Scala 2 MigrationBuilderSyntax provides dropField(selector) but lacks an overload that accepts defaultForReverse (which exists in the core builder API and is provided in the Scala 3 syntax). Adding a dropField(selector, defaultForReverse: DynamicSchemaExpr) macro overload would keep Scala 2/3 feature parity and avoid forcing users to fall back to DynamicOptic-based calls.

Suggested change

/**

/**

* Drop a field using a type-safe selector, providing a default expression

* for reverse migrations.

*/

def dropField[T](selector: A => T, defaultForReverse: DynamicSchemaExpr): MigrationBuilder[A, B] =

builder.dropField(MigrationBuilder.paths.from[A, T](selector), defaultForReverse)

/**

Godzilla675 added 14 commits February 5, 2026 18:22

docs(schema): add migration docs

a2b74b9

feat(migration): core model and schemas

7245fb4

feat(migration): builder and validation

2eb1b4d

feat(schema): structural derivation bindings

a94a183

feat(migration): selector macros and syntax

14d335d

test(migration): add migration coverage

efe5765

Apply scalafmt formatting to MigrationValidator

17f403c

Add branch coverage tests and fix scalafmt

620bd24

Add 413 migration coverage tests to meet 80% branch coverage minimum

f99eb13

Fix scalafmt formatting for MigrationBuilderSyntax.scala

f65031e

fix: scalafmt scala213 dialect, fix failing test, add coverage tests …

89a5820

…for branch gap

fix: JS compat, coercion assertions, add modifyAtPathRec and navigate…

8c5cee6

… coverage

Copilot AI review requested due to automatic review settings February 6, 2026 18:09

Copilot started reviewing on behalf of Godzilla675 February 6, 2026 18:09 View session

Copilot AI reviewed Feb 6, 2026

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Godzilla675 closed this Feb 6, 2026

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Add migration system coverage tests (550+ tests)#997

Add migration system coverage tests (550+ tests)#997
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Godzilla675:schema-migration-for-zio-schema-2-system-v3

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		modifyAtPathWithParentContext(value, at) { (_, targetValue) =>
		transform.eval(targetValue).left.map(wrapExprError(at, "TransformValue"))

-    /**
+    /**
+     * Drop a field using a type-safe selector, providing a default expression
+     * for reverse migrations.
+     */
+    def dropField[T](selector: A => T, defaultForReverse: DynamicSchemaExpr): MigrationBuilder[A, B] =
+      builder.dropField(MigrationBuilder.paths.from[A, T](selector), defaultForReverse)
+    /**

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