[Phase 2] Enable MSSQL JSON data type - type mapping & error codes (engine) by souvikghosh04 · Pull Request #3691 · Azure/data-api-builder

souvikghosh04 · 2026-07-01T13:51:59Z

What this PR does

Adds support for the SQL Server 2025 JSON column type by treating it exactly like a normal text (string) column. Reading, writing, filtering, and sorting all reuse the paths DAB already has for strings — no new type, no special handling.

The change

Two small edits to the engine:

Map the type — tell DAB that a JSON column is a string.
Map the errors — when SQL Server rejects invalid JSON, return HTTP 400 (Bad Request) instead of a generic 500.

Both are covered by new unit tests.

This PR is intentionally scoped to just the engine change. The database test table and end-to-end (REST/GraphQL) tests are not included here because they need a real SQL Server 2025 database — and our CI currently runs on LocalDB, which doesn't understand the JSON type yet. Those tests come in the next phase.

Delivery plan

Phase	What	Status
1	Upgrade to .NET 10 + SqlClient 6.x (prerequisite)	✅ Merged (#3656)
2	JSON type + error mapping	This PR
3	Test table + full REST/GraphQL/MCP tests	Next
4	Error/filter edge cases + regression	After

Notes

No changes to PostgreSQL, MySQL, DwSql, or CosmosDB.
Related issue: [Enh]: Support JSON data type for MSSQL #2768.

…s (Phase 2) Treat SQL Server 2025+ JSON columns exactly like string columns (2026-06-09 design, issue #2768). Engine-only change validated by unit tests. - TypeHelper._sqlDbTypeToType[SqlDbType.Json] = typeof(string) (T004) - SqlTypeConstants: register json as supported literal (T004) - MsSqlDbExceptionParser BadRequestExceptionCodes += 13608-13614 so SQL JSON errors map to HTTP 400 (T006) - unit tests for json type mapping and 400 error mapping (T005/T007) The profiles DB fixture (T002) and Profile config entity (T003) are DEFERRED to Phase 3: the native json type requires SQL Server 2025+/Azure SQL and cannot be created on the LocalDB engine used by CI. They ship with the Phase 3 integration tests behind server-version gating. No changes to PostgreSQL/MySQL/DwSql/CosmosDB (FR-012).

Copilot

Pull request overview

Adds SQL Server 2025 JSON column support by treating JSON exactly like a string in DAB’s type system, and improves error handling so SQL JSON validation failures map to a client error instead of a generic server error.

Changes:

Map SqlDbType.Json (and the "json" type literal) to CLR string so existing string read/write/filter/sort paths apply.
Map SQL Server JSON validation error codes (13608–13614) to HTTP 400 (Bad Request) in the MSSQL exception parser.
Add/extend tests validating the new type mapping and HTTP status mapping.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
src/Core/Services/TypeHelper.cs	Adds `SqlDbType.Json -> string` mapping so JSON behaves like a string in CLR/type resolution.
src/Core/Models/SqlTypeConstants.cs	Marks `"json"` as a supported SQL type literal for metadata/type-resolution test coverage.
src/Core/Resolvers/MsSqlDbExceptionParser.cs	Adds JSON validation error codes to the “bad request” classification.
src/Service.Tests/OpenApiDocumentor/CLRtoJsonValueTypeUnitTests.cs	Adds a targeted test asserting `"json"` resolves to `string` and maps to `JsonDataType.String`.
src/Service.Tests/UnitTests/DbExceptionParserUnitTests.cs	Adds a data-driven test asserting JSON validation errors map to HTTP 400.

RubenCerna2079

Looks good to me, but the tests will need to be changed as the pipeline should be able to support the JSON data type with this PR. #3697

RubenCerna2079

LGTM! Just address the comments made by copilot.

## What this PR does Adds the database test fixture and REST integration tests for SQL Server 2025 `JSON` columns. It builds on Phase 2 (which taught the engine to treat `JSON` as a normal `string`) and proves the behavior end-to-end through the REST API. This follows the exact pattern of the recently merged **vector data type** feature (#3677), and is unblocked by CI now running SQL Server 2025 (#3697). ## What's included - **Test table** — a `profiles` table with an `id` and a `metadata json` column, plus 5 seed rows covering a simple object, an array, a deeply nested object, unicode + emoji, and `NULL`. - **Entity** — a `Profile` entity (REST + GraphQL enabled) in the MsSql test config and config generator. - **REST tests** — `MsSqlRestJsonTypesTests`: read (list, by id, null, array, nested, unicode), insert, update (PUT/PATCH), clear-to-null, and delete. Because DAB treats `JSON` as a string, the tests parse `metadata` and compare it **semantically**, so they're robust to any whitespace / key-order normalization the engine applies. ## No gating needed Unlike the earlier plan, the table is created **unconditionally** (no server-version guard) — CI runs SQL Server 2025 and the schema already uses the 2025-only `vector` type the same way. ## Delivery plan | Phase | What | Status | |------|------|--------| | 1 | .NET 10 + SqlClient 6.x (prerequisite) | ✅ Merged (#3697/#3656) | | 2 | JSON type + error mapping (engine) | ✅ Merged (#3691) | | **3** | **Test fixture + REST CRUD tests (this PR)** | 🚧 In review | | 3b | GraphQL / OpenAPI / MCP schema-discovery tests | Next | | 4 | Error/filter edge cases + regression | After | ## Notes - Requires SQL Server 2025 / Azure SQL (native `json` type). - No changes to PostgreSQL, MySQL, DwSql, or CosmosDB. - Related issue: #2768. --------- Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

@aaronburtle

…QL tests (#3738) ## Why Part of MSSQL native `JSON` support (#2768). Started as Phase 3b **schema-discovery tests**, but review (thanks @aaronburtle) surfaced a real product inconsistency that this PR now also fixes. **The problem:** #2768 requires a `JSON` column to be treated as a normal `string` for **input and output**. But the MSSQL read path (`FOR JSON PATH`) was *inlining* a native `json` column as a nested JSON **object**. Consequences: - REST returned `"metadata": {"role":"admin"}` (object) instead of `"metadata": "{\"role\":\"admin\"}"` (string). - A GraphQL read of the `String`-typed field threw a `GraphQLMapping` error — the `String` leaf resolver calls `JsonElement.GetString()`, which fails on an object. So schema introspection could pass while `profile_by_pk(id:1){ metadata }` failed at runtime. - OpenAPI/GraphQL advertised `string`, contradicting the object runtime — generated clients would mis-model the field. ## What **Engine fix** (`MsSqlQueryBuilder`): the read path now casts a native `json` column (`SqlDbType.Json`) to `NVARCHAR(MAX)` in `WrappedColumns`, so `FOR JSON PATH` emits it as an escaped JSON **string** rather than inlining it as an object. This is the single choke point for REST **and** GraphQL reads. Regular `nvarchar` columns are untouched. Mutations already return `json` as a string via the tabular `OUTPUT` clause, so no change was needed there. **Tests:** | Layer | Test | Asserts | |------|------|---------| | OpenAPI | `JsonTypeSchemaTests` | `metadata` is `type: string` with no `format` in the **response** and both **request-body** schemas (`Profile_NoAutoPK` for POST, `Profile_NoPK` for PUT/PATCH) | | GraphQL introspection | `MsSqlGraphQLJsonSchemaTests` | `Profile.metadata` is the built-in `String` scalar (no custom JSON scalar) | | GraphQL read (new) | `MsSqlGraphQLJsonSchemaTests` | `profile_by_pk(id:1){ metadata }` returns the payload as a JSON **string** — guards against introspection passing while a real read throws | | REST | `MsSqlRestJsonTypesTests` (updated) | flipped back to the string contract: `metadata` is returned as a JSON **string** (`ParseMetadata`/`GetJsonTypeList` assert `JsonValueKind.String`) | > Note: DAB's OpenAPI documentor does not emit `Nullable` on the property schema for **any** column type, so the schema tests assert `type: string` + no `format` (not nullability). ## Intentionally omitted - **MCP `describe_entities` (T010)**: it projects only the config field `name`/`description`, not DB column data types, so there is no JSON-specific behavior to assert. ## Notes - **This PR now includes a product (engine) change**, not tests only. - Requires SQL Server 2025 / Azure SQL (native `json`); CI already runs SQL 2025. - Cannot be run locally (no SQL 2025 here) — relying on CI. ## Delivery plan | Phase | What | Status | |-------|------|--------| | 1 | .NET 10 + SqlClient 6.x | ✅ Merged (#3697/#3656) | | 2 | JSON type + error mapping (engine) | ✅ Merged (#3691) | | 3 | Test fixture + REST CRUD tests | ✅ Merged (#3720) | | **3b** | **json-as-string read fix + OpenAPI/GraphQL discovery & read tests (this PR)** | 🚧 | | 4 | Error/filter edge cases + regression + polish | Next |

souvikghosh04 force-pushed the Usr/sogh/mssql-json-phase2 branch from 4edabac to 6bed2da Compare July 1, 2026 13:54

souvikghosh04 force-pushed the Usr/sogh/mssql-json-phase2 branch from 6bed2da to 9e5a38d Compare July 1, 2026 14:07

souvikghosh04 changed the title ~~[Phase 2] Enable MSSQL JSON data type - type mapping, error codes & fixtures~~ [Phase 2] Enable MSSQL JSON data type - type mapping & error codes (engine) Jul 1, 2026

souvikghosh04 marked this pull request as ready for review July 2, 2026 09:43

Copilot AI review requested due to automatic review settings July 2, 2026 09:43

souvikghosh04 requested review from Alekhya-Polavarapu, Aniruddh25, JerryNixon, RubenCerna2079, aaronburtle, anushakolan, rusamant, sourabh1007, stuartpa and vadeveka as code owners July 2, 2026 09:43

souvikghosh04 self-assigned this Jul 2, 2026

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github-project-automation Bot moved this to Todo in Data API builder Jul 2, 2026

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Copilot started reviewing on behalf of souvikghosh04 July 2, 2026 09:43 View session

souvikghosh04 linked an issue Jul 2, 2026 that may be closed by this pull request

Phase 2: Map type and error code for JSON datatype #3692

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souvikghosh04 moved this from Todo to Review In Progress in Data API builder Jul 2, 2026

Copilot AI reviewed Jul 2, 2026

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Comment thread src/Core/Resolvers/MsSqlDbExceptionParser.cs

Comment thread src/Service.Tests/UnitTests/DbExceptionParserUnitTests.cs

Merge branch 'main' into Usr/sogh/mssql-json-phase2

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RubenCerna2079 reviewed Jul 7, 2026

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RubenCerna2079 approved these changes Jul 9, 2026

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Copilot started work on behalf of souvikghosh04 July 13, 2026 07:47 View session

fix mssql json graphql substatus mapping

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Copilot finished work on behalf of souvikghosh04 July 13, 2026 07:53

Copilot finished work on behalf of souvikghosh04 July 13, 2026 07:54

Copilot started work on behalf of souvikghosh04 July 13, 2026 11:50 View session

Copilot finished work on behalf of souvikghosh04 July 13, 2026 11:53

Merge branch 'main' into Usr/sogh/mssql-json-phase2

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anushakolan approved these changes Jul 14, 2026

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Merge branch 'main' into Usr/sogh/mssql-json-phase2

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souvikghosh04 enabled auto-merge (squash) July 14, 2026 12:13

souvikghosh04 merged commit 15fcfa5 into main Jul 14, 2026
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souvikghosh04 deleted the Usr/sogh/mssql-json-phase2 branch July 14, 2026 12:55

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[Phase 3] MSSQL JSON - test fixture + REST CRUD tests #3720

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This was referenced Jul 28, 2026

[Phase 3b] MSSQL JSON - return json as string on read + OpenAPI/GraphQL tests #3738

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[Phase 3b] MSSQL JSON - OpenAPI + GraphQL schema-discovery tests #3739

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[Phase 2] Enable MSSQL JSON data type - type mapping & error codes (engine) - #3691

[Phase 2] Enable MSSQL JSON data type - type mapping & error codes (engine)#3691
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souvikghosh04 commented Jul 1, 2026 •

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souvikghosh04 commented Jul 1, 2026 •

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