Transform JSON / JSONB parameter keys

[karlhorky]

Hey @porsager, hope you're good! 👋

Postgres.js transforms JS property names passed through sql(...) helpers, eg. with { transform: postgres.camel }:

sql({ firstName: 'Ada' }) // { first_name: 'Ada' }

However, currently JSON parameter keys are not transformed 💥

sql.json({ firstName: 'Ada' }) // {"firstName":"Ada"}

Maybe this was an oversight in my previous PR for "nested transforms":

• Add nested transforms #460

This PR adds JSON value transforms before serialization for the built-in case transforms, so JSON and JSONB parameters serialize transformed keys:

sql.json({ firstName: 'Ada' }) // {"first_name":"Ada"}

This change also applies to JSON / JSONB data created via sql.typed() and type casts:

sql.typed({ firstName: 'Ada' }, 114) // {"first_name":"Ada"}
sql`${ { firstName: 'Ada' } }::jsonb` // {"first_name":"Ada"}

• Transform JSON / JSONB parameter keys
• Add value.to transforms for camel, pascal, and kebab
• Test nested objects, arrays, result parsing, and untransformed JSON
• Test implicit and typed JSON parameters
• Update types

AI disclosure: guided use of gpt-5.5 high through Codex CLI

[Copilot]

Pull request overview

Note

Copilot was unable to run its full agentic suite in this review.

This PR extends the library’s transform system so JSON parameter serialization can apply key-casing transforms (e.g., camelCase ⇄ snake_case), and updates typings + tests accordingly.

Changes:

• Apply transform.value.to during JSON serialization (for JSON/JSONB parameters).
• Add value.to transform helpers for camel/pascal/kebab transforms.
• Update TypeScript declarations and expand JSON transform test coverage across builds (node/deno/cjs).

Reviewed changes

Copilot reviewed 11 out of 13 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
types/index.d.ts	Updates public typings for transform value-direction helpers and serializer signatures.
src/types.js	Applies transform-on-JSON-serialize and wires up value.to for casing transforms.
src/connection.js	Passes parsed options into serializers.
tests/index.js	Adds coverage for JSON key transforms on parameters/results.
deno/types/index.d.ts	Mirrors typing changes for Deno build.
deno/src/types.js	Mirrors JSON serialization + transform wiring for Deno build.
deno/src/connection.js	Mirrors passing options into serializers for Deno build.
deno/tests/index.js	Mirrors JSON transform tests for Deno build.
cjs/src/types.js	Mirrors JSON serialization + transform wiring for CJS build.
cjs/src/connection.js	Mirrors passing options into serializers for CJS build.
cjs/tests/index.js	Mirrors JSON transform tests for CJS build.
cf/src/types.js	Mirrors JSON serialization + transform wiring for CF build.
cf/src/connection.js	Mirrors passing options into serializers for CF build.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[karlhorky]

only transform plain objects, to avoid transforming objects like Dates

[karlhorky]

@porsager I think this is ready for a review

[porsager]

Nice @karlhorky - Only problem is that this is a breaking change, so I think the behaviour would need to be something toggled by an option??

[karlhorky]

@porsager yeah technically it's a breaking change to the current behavior.

Although arguably, the original promise of the postgres.camel transform was bidirectional transforms, so in that light it could be considered a "bug fix".

But yeah, to make the library updates less surprising, it's better to consider it as a breaking change, in case users are depending on the half-baked behavior.

Maybe a solution would be to release it in a new major version postgres@4.0.0 - what do you think?