http-client-java, support array encoded as CSV on property #9218

weidongxu-microsoft · 2025-12-16T05:16:13Z

see https://github.com/microsoft/typespec/pull/9218/files#diff-e8b978e5080675f7527d4beb363a9dde604493dbff1db49116ea56c94b2339e1 on difference on generated code.

Currently only supports element as String. (the convert from a subtype to String need some refactor in existing code)

release PR is Azure/autorest.java#3242

github-actions · 2025-12-16T05:19:03Z

No changes needing a change description found.

azure-sdk · 2025-12-16T05:34:31Z

You can try these changes here

🛝 Playground	🌐 Website	🛝 VSCode Extension

weidongxu-microsoft · 2025-12-16T06:23:13Z

...-test/src/test/java/azure/clientgenerator/core/clientlocation/ClientLocationClientTests.java

This is not related to this PR/feature.

Removed due to failure in nightly build, because an unreleased commit there breaked this test into 4 tests. Hence test code here won't compile on dev.

Need to be added back in next typespec version bump. #9220

Copilot

Pull request overview

This PR adds support for delimited array encoding (CSV and other formats) on properties in the http-client-java emitter. The implementation allows TypeSpec models to specify how arrays of strings should be serialized as delimited strings in JSON (comma, space, pipe, or newline-delimited) instead of as JSON arrays. The changes span the code generator, model templates, and include both Azure and clientcore test implementations.

Key Changes

Introduces ArrayEncoding enum to define delimiter strategies for array serialization
Extends ClientModelProperty to include array encoding metadata
Updates serialization/deserialization templates to handle delimited string encoding
Adds validation to ensure only string element types are supported for array encoding

Reviewed changes

Copilot reviewed 22 out of 23 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
packages/http-client-java/package.json	Updates TypeSpec compiler and various dev dependencies to newer versions
packages/http-client-java/package-lock.json	Lockfile updates corresponding to package.json changes
packages/http-client-java/generator/http-client-generator-test/src/test/java/encode/array/EncodeArrayTests.java	New test suite for array encoding with comma, space, pipe, and newline delimiters
packages/http-client-java/generator/http-client-generator-test/src/test/java/azure/clientgenerator/core/clientlocation/ClientLocationClientTests.java	Test file removed (appears to be replaced by generated tests)
packages/http-client-java/generator/http-client-generator-test/src/main/java/encode/array/models/*.java	Generated model classes implementing delimiter-based serialization for different array encoding types
packages/http-client-java/generator/http-client-generator-core/src/main/java/com/microsoft/typespec/http/client/generator/core/template/StreamSerializationModelTemplate.java	Updates toJson/fromJson generation to handle array encoding with delimiter-based string serialization
packages/http-client-java/generator/http-client-generator-core/src/main/java/com/microsoft/typespec/http/client/generator/core/model/clientmodel/ClientModelProperty.java	Adds arrayEncoding field to track delimiter configuration
packages/http-client-java/generator/http-client-generator-core/src/main/java/com/microsoft/typespec/http/client/generator/core/model/clientmodel/ArrayEncoding.java	New enum defining delimiter types and their escape sequences
packages/http-client-java/generator/http-client-generator-core/src/main/java/com/microsoft/typespec/http/client/generator/core/mapper/ModelPropertyMapper.java	Maps array encoding metadata from TypeSpec model to Java property
packages/http-client-java/generator/http-client-generator-core/src/main/java/com/microsoft/typespec/http/client/generator/core/extension/model/codemodel/Property.java	Adds arrayEncoding field to Property model
packages/http-client-java/generator/http-client-generator-clientcore-test/src/*/.java	Clientcore test implementations mirroring the Azure test structure
packages/http-client-java/emitter/src/lib.ts	Adds diagnostic for unsupported non-string array encoding elements
packages/http-client-java/emitter/src/common/client.ts	Defines EncodedProperty interface for array encoding metadata
packages/http-client-java/emitter/src/code-model-builder.ts	Validates string element type requirement and maps array encoding to code model

Files not reviewed (1)

packages/http-client-java/package-lock.json: Language not supported

.../java/com/microsoft/typespec/http/client/generator/core/model/clientmodel/ArrayEncoding.java

Copilot · 2025-12-16T06:33:28Z

...microsoft/typespec/http/client/generator/core/template/StreamSerializationModelTemplate.java

+                    methodBlock.ifBlock(propertyValueGetter + " != null", ifBlock -> {
+                        String serializeExpression = propertyValueGetter
+                            + ".stream().map(element -> element == null ? \"\" : element).collect(Collectors.joining(\""
+                            + property.getArrayEncoding().getDelimiter() + "\"))";
+                        methodBlock.line("jsonWriter.writeStringField(\"%s\", %s);", serializedName,
+                            serializeExpression);
+                    });


When serializing array elements, null elements are converted to empty strings with "element == null ? "" : element". However, during deserialization with split(), there's no corresponding logic to convert empty strings back to null. This creates an asymmetry where null array elements become empty strings after a round-trip serialization/deserialization cycle. Consider either preserving null elements differently (e.g., using a special placeholder) or documenting that null elements will be converted to empty strings.

This is valid concern. Had this in mind, particularly when the element type is utcDateTime, where empty string can only be mapped to null (no valid time on "").

However, for string, "" is valid.

...microsoft/typespec/http/client/generator/core/template/StreamSerializationModelTemplate.java

weidongxu-microsoft · 2025-12-16T06:43:12Z

...client-generator-clientcore-test/src/main/java/encode/array/CommaDelimitedArrayProperty.java

+            jsonWriter.writeStringField("value",
+                this.value.stream().map(element -> element == null ? "" : element).collect(Collectors.joining(",")));


Both null and "" would map to same encoded string.

On the other direction, currently we map e.g. "," to ["", ""] for string element.
For other type that extend string, we may choose differently (or even break this behavior on string type too), e.g. "," on utcDateTime/uuid can only be [null, null]

Just hope service knows what it does on these...

...client-generator-clientcore-test/src/main/java/encode/array/CommaDelimitedArrayProperty.java

haolingdong-msft

Overall looks good to me. Add a nit. Thanks!

haolingdong-msft · 2025-12-16T09:51:12Z

...microsoft/typespec/http/client/generator/core/template/StreamSerializationModelTemplate.java

+                        isJsonMergePatch);
+                } else {
+                    // wireType is String
+                    // at present, only String element is supported


only String element is supported

nit: Do we want to add check here to mak sure the element type is string? Or could we at least mention we have the on emitter: https://github.com/microsoft/typespec/pull/9218/files#diff-a10993e19db8ea9bd765f4d6abeaff1624f8f9a3842b9203c207f07527ef3d2eR2869
Because I tried to find in the code below that do the check on supporting string element only, but seems did not find it. (happy to be corrected)

js code would error when element is not String. https://github.com/microsoft/typespec/pull/9218/files#diff-3b4a90c1f1304a9d5376a1303d121b44f4d136282666142484ee61f445d540c6

haolingdong-msft · 2025-12-16T09:51:35Z

...ttp-client-generator-test/src/main/java/encode/array/models/CommaDelimitedArrayProperty.java

    public JsonWriter toJson(JsonWriter jsonWriter) throws IOException {
        jsonWriter.writeStartObject();
-        jsonWriter.writeArrayField("value", this.value, (writer, element) -> writer.writeString(element));
+        if (this.value != null) {


Generated code looks good to me.

weidongxu-microsoft added 6 commits December 15, 2025 14:30

add arrayEncode to Property

05abb2c

add ArrayEncoding

b71290e

support element type String

26bb131

regen

66f1c3a

test by agent

5b32626

bug fix

03b8567

microsoft-github-policy-service bot added the emitter:client:java Issue for the Java client emitter: @typespec/http-client-java label Dec 16, 2025

weidongxu-microsoft added 5 commits December 16, 2025 13:54

regen

441d8b3

test in cliencore

9515a85

log error if element type is not string

531a42f

remove ClientLocationClientTests to pass nightly build

d4ca7ef

bump dependencies

cd11ae7

weidongxu-microsoft commented Dec 16, 2025

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weidongxu-microsoft requested a review from Copilot December 16, 2025 06:28

Copilot started reviewing on behalf of weidongxu-microsoft December 16, 2025 06:29 View session

Copilot AI reviewed Dec 16, 2025

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weidongxu-microsoft changed the title ~~http-client-java, support csv on property~~ http-client-java, support array encoded as CSV on property Dec 16, 2025

weidongxu-microsoft marked this pull request as ready for review December 16, 2025 06:40

weidongxu-microsoft requested review from XiaofeiCao, anuchandy, haolingdong-msft and srnagar as code owners December 16, 2025 06:40

weidongxu-microsoft commented Dec 16, 2025

View reviewed changes

...client-generator-clientcore-test/src/main/java/encode/array/CommaDelimitedArrayProperty.java Outdated Show resolved Hide resolved

comment

3d0d060

haolingdong-msft approved these changes Dec 16, 2025

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weidongxu-microsoft added 2 commits December 17, 2025 10:20

unit test for corner cases

086ee5b

bug fix and regen

fd843b1

weidongxu-microsoft force-pushed the http-client-java_support-csv-on-property branch from bdc3cbd to fd843b1 Compare December 17, 2025 03:24

format

805e28d

weidongxu-microsoft mentioned this pull request Dec 17, 2025

eng, prepare release 0.37.4 Azure/autorest.java#3242

Draft

weidongxu-microsoft added 2 commits December 17, 2025 11:53

one more test

20bb4c0

format

883929b

XiaofeiCao approved these changes Dec 17, 2025

View reviewed changes

		jsonWriter.writeStringField("value",
		this.value.stream().map(element -> element == null ? "" : element).collect(Collectors.joining(",")));

http-client-java, support array encoded as CSV on property #9218

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Pull request overview

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