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Implement client error correction
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‎codegen/core/src/main/java/software/amazon/smithy/python/codegen/generators/MemberErrorCorrectionGenerator.java‎

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/*
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* Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
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* SPDX-License-Identifier: Apache-2.0
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*/
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package software.amazon.smithy.python.codegen.generators;
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import software.amazon.smithy.model.shapes.BigDecimalShape;
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import software.amazon.smithy.model.shapes.BigIntegerShape;
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import software.amazon.smithy.model.shapes.BlobShape;
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import software.amazon.smithy.model.shapes.BooleanShape;
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import software.amazon.smithy.model.shapes.ByteShape;
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import software.amazon.smithy.model.shapes.DocumentShape;
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import software.amazon.smithy.model.shapes.DoubleShape;
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import software.amazon.smithy.model.shapes.EnumShape;
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import software.amazon.smithy.model.shapes.FloatShape;
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import software.amazon.smithy.model.shapes.IntEnumShape;
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import software.amazon.smithy.model.shapes.IntegerShape;
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import software.amazon.smithy.model.shapes.ListShape;
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import software.amazon.smithy.model.shapes.LongShape;
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import software.amazon.smithy.model.shapes.MapShape;
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import software.amazon.smithy.model.shapes.MemberShape;
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import software.amazon.smithy.model.shapes.Shape;
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import software.amazon.smithy.model.shapes.ShapeVisitor;
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import software.amazon.smithy.model.shapes.ShortShape;
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import software.amazon.smithy.model.shapes.StringShape;
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import software.amazon.smithy.model.shapes.StructureShape;
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import software.amazon.smithy.model.shapes.TimestampShape;
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import software.amazon.smithy.model.shapes.UnionShape;
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import software.amazon.smithy.model.traits.StreamingTrait;
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import software.amazon.smithy.python.codegen.GenerationContext;
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import software.amazon.smithy.python.codegen.SymbolProperties;
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import software.amazon.smithy.python.codegen.writer.PythonWriter;
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import software.amazon.smithy.utils.SmithyInternalApi;
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/**
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* Emits the Python expression used to fill a missing required member during client error
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* correction.
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*
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* @see <a href="https://smithy.io/2.0/spec/aggregate-types.html#client-error-correction">Smithy
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* spec: Client error correction</a>
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*/
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@SmithyInternalApi
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public final class MemberErrorCorrectionGenerator extends ShapeVisitor.DataShapeVisitor<Boolean> {
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private final GenerationContext context;
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private final PythonWriter writer;
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public MemberErrorCorrectionGenerator(GenerationContext context, PythonWriter writer) {
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this.context = context;
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this.writer = writer;
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}
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/**
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* @return {@code true} if the visitor will emit a default expression for this shape.
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*/
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public static boolean hasDefault(Shape target) {
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return switch (target.getType()) {
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// Note on streaming shapes:
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// - Streaming unions (event streams) are filtered out earlier by
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// StructureGenerator#filterEventStreamMember and never reach this visitor,
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// so UNION can unconditionally return true here.
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// - Streaming blobs are NOT filtered earlier, so we explicitly exclude them
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// below. Per Smithy spec § 13.3.1, a missing streaming blob is already
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// handled by the deserializer (an empty HTTP body becomes a zero-length
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// AsyncBytesReader), so client error correction is unnecessary.
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case BOOLEAN, BYTE, SHORT, INTEGER, LONG, BIG_INTEGER, FLOAT, DOUBLE, BIG_DECIMAL,
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STRING, TIMESTAMP, DOCUMENT, LIST, MAP, ENUM, INT_ENUM, STRUCTURE, UNION ->
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true;
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case BLOB -> !target.hasTrait(StreamingTrait.class);
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default -> false;
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};
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}
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@Override
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public Boolean booleanShape(BooleanShape shape) {
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writer.writeInline("False");
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return true;
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}
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@Override
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public Boolean byteShape(ByteShape shape) {
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writer.writeInline("0");
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return true;
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}
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@Override
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public Boolean shortShape(ShortShape shape) {
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writer.writeInline("0");
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return true;
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}
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@Override
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public Boolean integerShape(IntegerShape shape) {
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writer.writeInline("0");
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return true;
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}
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@Override
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public Boolean longShape(LongShape shape) {
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writer.writeInline("0");
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return true;
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}
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@Override
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public Boolean bigIntegerShape(BigIntegerShape shape) {
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writer.writeInline("0");
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return true;
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}
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@Override
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public Boolean floatShape(FloatShape shape) {
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writer.writeInline("0.0");
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return true;
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}
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@Override
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public Boolean doubleShape(DoubleShape shape) {
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writer.writeInline("0.0");
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return true;
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}
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@Override
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public Boolean bigDecimalShape(BigDecimalShape shape) {
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writer.addStdlibImport("decimal", "Decimal");
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writer.writeInline("Decimal(0)");
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return true;
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}
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@Override
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public Boolean stringShape(StringShape shape) {
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writer.writeInline("\"\"");
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return true;
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}
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@Override
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public Boolean blobShape(BlobShape shape) {
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writer.writeInline("b\"\"");
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return true;
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}
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@Override
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public Boolean timestampShape(TimestampShape shape) {
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writer.addStdlibImport("datetime", "datetime");
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writer.addStdlibImport("datetime", "timezone");
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writer.writeInline("datetime.fromtimestamp(0, tz=timezone.utc)");
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return true;
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}
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@Override
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public Boolean documentShape(DocumentShape shape) {
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writer.addImport("smithy_core.documents", "Document");
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writer.writeInline("Document(None)");
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return true;
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}
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@Override
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public Boolean listShape(ListShape shape) {
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writer.writeInline("[]");
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return true;
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}
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@Override
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public Boolean mapShape(MapShape shape) {
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writer.writeInline("{}");
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return true;
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}
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@Override
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public Boolean enumShape(EnumShape shape) {
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// TODO: the Smithy spec recommends enum types define an unknown variant. If a
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// future change adds an unknown variant to the generated enum class (e.g.
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// MyEnum.unknown(value)), revisit this to emit it instead of the bare "".
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writer.writeInline("\"\"");
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return true;
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}
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@Override
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public Boolean intEnumShape(IntEnumShape shape) {
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// TODO: the Smithy spec recommends intEnum types define an unknown variant. If a
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// future change adds an unknown variant to the generated intEnum class (e.g.
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// MyIntEnum.unknown(value)), revisit this to emit it instead of the bare 0.
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writer.writeInline("0");
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return true;
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}
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@Override
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public Boolean unionShape(UnionShape shape) {
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var unknownSymbol = context.symbolProvider()
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.toSymbol(shape)
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.expectProperty(SymbolProperties.UNION_UNKNOWN);
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writer.addImport(unknownSymbol, unknownSymbol.getName());
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writer.writeInline("$L(tag=\"\")", unknownSymbol.getName());
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return true;
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}
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@Override
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public Boolean structureShape(StructureShape shape) {
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// Delegate to the target struct's _smithy_default() so nested required fields are
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// also filled in. Recursion terminates because Smithy forbids recursive paths whose
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// members are all @required:
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// https://smithy.io/2.0/spec/aggregate-types.html#recursive-shape-definitions
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var symbol = context.symbolProvider().toSymbol(shape);
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writer.addImport(symbol, symbol.getName());
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writer.writeInline("$L._smithy_default()", symbol.getName());
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return true;
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}
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@Override
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public Boolean memberShape(MemberShape shape) {
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return context.model().expectShape(shape.getTarget()).accept(this);
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}
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}

‎codegen/core/src/main/java/software/amazon/smithy/python/codegen/generators/StructureGenerator.java‎

Lines changed: 73 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -104,12 +104,15 @@ class $L:
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${C|}
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${C|}
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""",
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symbol.getName(),
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writer.consumer(w -> writeClassDocs()),
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writer.consumer(w -> writeProperties()),
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writer.consumer(w -> generateSerializeMethod()),
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writer.consumer(w -> generateDeserializeMethod()));
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writer.consumer(w -> generateDeserializeMethod()),
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writer.consumer(w -> generateSmithyDefaultMethod()));
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}
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private void renderError() {
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${7C|}
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${8C|}
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""",
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symbol.getName(),
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baseError,
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fault,
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writer.consumer(w -> writeClassDocs()),
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writer.consumer(w -> writeProperties()),
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writer.consumer(w -> generateSerializeMethod()),
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writer.consumer(w -> generateDeserializeMethod()));
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writer.consumer(w -> generateDeserializeMethod()),
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writer.consumer(w -> generateSmithyDefaultMethod()));
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}
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private void writeClassDocs() {
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logger.debug("Unexpected member schema: %s", schema)
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deserializer.read_struct($T, consumer=_consumer)
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${C|}
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return kwargs
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""",
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writer.consumer(w -> deserializeMembers(shape.members())),
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schemaSymbol);
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schemaSymbol,
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writer.consumer(w -> writeErrorCorrection()));
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writer.popState();
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}
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/**
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* Emits client error correction for required members the server failed to serialize.
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*
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* @see <a href="https://smithy.io/2.0/spec/aggregate-types.html#client-error-correction">Smithy
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* spec: Client error correction</a>
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*/
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private void writeErrorCorrection() {
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var visitor = new MemberErrorCorrectionGenerator(context, writer);
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for (MemberShape member : requiredMembers) {
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var target = model.expectShape(member.getTarget());
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if (!MemberErrorCorrectionGenerator.hasDefault(target)) {
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// Streaming shapes have no synthesizable default; let the dataclass raise.
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continue;
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}
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writer.pushState();
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writer.putContext("memberName", symbolProvider.toMemberName(member));
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writer.write("""
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if ${memberName:S} not in kwargs:
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kwargs[${memberName:S}] = ${C|}""",
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writer.consumer(w -> target.accept(visitor)));
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writer.popState();
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}
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}
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/**
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* Emits a {@code _smithy_default()} classmethod that constructs an instance with all
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* required members filled in via client error correction. Used to fill nested structure
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* members per the Smithy spec. If the structure has any required member whose target has
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* no synthesizable default (i.e. a streaming blob), {@code _smithy_default()} is omitted:
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* a generated {@code cls()} call would be missing a required argument. But such structures
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* can only appear as a top-level operation input or output (per spec § 13.3), never as a
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* nested-struct member, so {@code _smithy_default()} would never be invoked on them anyway.
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*/
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private void generateSmithyDefaultMethod() {
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for (MemberShape member : requiredMembers) {
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var target = model.expectShape(member.getTarget());
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if (!MemberErrorCorrectionGenerator.hasDefault(target)) {
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return;
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}
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}
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writer.write("""
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@classmethod
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def _smithy_default(cls) -> Self:
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return cls(${C|})
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""",
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writer.consumer(w -> writeSmithyDefaultArguments()));
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}
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private void writeSmithyDefaultArguments() {
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var visitor = new MemberErrorCorrectionGenerator(context, writer);
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var first = true;
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for (MemberShape member : requiredMembers) {
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var target = model.expectShape(member.getTarget());
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if (!first) {
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writer.writeInline(", ");
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}
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first = false;
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writer.writeInline("$L=", symbolProvider.toMemberName(member));
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target.accept(visitor);
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}
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}
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private void deserializeMembers(Collection<MemberShape> members) {
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int index = -1;
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for (MemberShape member : members) {

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