fix: apply a field's `@nexus.default` to an optional resource method parameter in Python by moetemp · Pull Request #408 · temporalio/nexgen

moetemp · 2026-11-13T17:11:40Z

This PR makes a Python resource method apply a request field's @nexus.default to an optional parameter with the field's name.

The method passed the parameter as it was, so a call with no value sent none. TypeScript and .NET already apply the default in the operation.

record append-records-request {
  /// @nexus.default targets="client" python="_support.default_producer()" ...
  producer: producer,
}

append: func(records: list<append-record>, producer: option<producer>, sequence: option<s64>) -> append-records-response;

producer=((_support.default_producer()) if producer is None else producer),

The stream sample's append and close take an optional producer this way. Its two producer fields have a default now, not a source.

A resource with `@nexus.type-parameter "<alias>"` is generic in Python, TypeScript and .NET. An operation that returns it, or that its method binds, takes a runtime type for each type parameter of its output, so a response decodes its generic values.

The kept fixtures cover an undeclared type parameter, a generic resource in a record field or in a result with no proto message, and a language that refuses it. The others test directive syntax, rare name clashes or another copy of a kept check.

Co-authored-by: Tim Conley <timothy.conley@temporal.io>

A resource that uses a type parameter, also through its records, is generic in it, as a record is. So a resource needs no annotation, and `@nexus.type-parameter` is valid only on a type alias again.

Only a returned resource gives its type parameters, as the guide says, so a parameter or field that holds one doesn't. The declaration order doesn't change when a method moves.

A list, map, tuple, result or variant case builds the resource from the record's message too, so it gets no type argument either.

The old reason said a proto message holds the type arguments, which it doesn't.

Two type parameters such as `body` and `body-t` give the same runtime type name, and a method can take it too. Either one makes a duplicate parameter or member.

The typed hook of a generic response took only the request, so the terminal decoded `ReadRecordsResponse[Turn]` with the plain class and lost `Turn`.

C# generics are invariant, so the `<object>` checks refused a `Stream<Turn>` call. The dispatch now compares generic type definitions and keeps the call's types.

A subclass such as `class TurnStream(Stream[Turn])` has no `__orig_class__`, so the handle reads `__orig_bases__` too. A factory tests `body_type is None`, since a class can be falsy.

The TypeScript stream test now decodes a body with a runtime type. The Python test decodes to the bare handle class, since a generic alias fails for another reason.

No release has the Python constructor change, so it belongs with the added entry. The fixed entry now describes the System Nexus dispatch fixes.

A few comments used "name" as a verb, ran over two lines or over 100 columns. The guide's first paragraph read as one long sentence.

Drop the tests that repeat another test or restate generated code, and keep the ones that guard behavior. Shorten the guide section and the comments.

Python can't subscript a function, so each generic call is an object whose subscript binds the types, as in `client.get_stream[Turn](ref=ref)`. A factory's optional field defaults to `None`. Co-authored-by: Tim Conley <timothy.conley@temporal.io>

`@nexus.close` marks the method that ends a resource. Python calls it at the end of `async with`, and a call that returns the resource returns a `ResourceCall`. Co-authored-by: Tim Conley <timothy.conley@temporal.io>

`@nexus.varargs` makes a resource method take a list's items as positional arguments, and a list of a flattened one-field record takes that field's values. The Stream's publish takes values and returns the last offset. Co-authored-by: Tim Conley <timothy.conley@temporal.io>

Workflow code gets a handle on an existing Stream with `get_stream[T]`, from the fields of its ref, with no call. Co-authored-by: Tim Conley <timothy.conley@temporal.io>

Each client call and client resource method takes `rpc_metadata` and `rpc_timeout`, and passes them to the `start_operation` of its Nexus client. Co-authored-by: Tim Conley <timothy.conley@temporal.io>

`@nexus.flatten-in-api` on a request field makes that call take the fields of the field's record, and the models keep the record. The Stream create takes the id, the owner and the backend of its ref this way, and the other Stream calls keep `ref`. Co-authored-by: Tim Conley <timothy.conley@temporal.io>

A field can leave the API of one target and take a source in another. A call of a target that omits a required list sends it empty. Co-authored-by: Tim Conley <timothy.conley@temporal.io>

The docs of both `producer` fields match the API's WIT, which has the two optional parameters. Co-authored-by: Tim Conley <timothy.conley@temporal.io>

The API gave `append` an optional `sequence`, so a caller can number a batch and the Store can dedupe a resent one. The optional `producer` parameter still waits for the generator change. Co-authored-by: Tim Conley <timothy.conley@temporal.io>

The sync gave `append` its optional `sequence`, and this branch puts it after `producer` as the API's WIT does. The generated samples were rebuilt, not merged by hand.

The API now says that two offsets of one Stream compare bytewise. It also says that Workflow code on a Store writes through a Local Activity. Only comments changed, so the samples only move in docs. Co-authored-by: Tim Conley <timothy.conley@temporal.io>

The sync brings the API's new offset and Workflow Producer comments, which this branch also needs. Co-authored-by: Tim Conley <timothy.conley@temporal.io>

…409) The SDK's `Client` inherits the generated extension, so `temporalio.client` imports the generated package. A run-time import back made importing the package first a circular import. Co-authored-by: Tim Conley <timothy.conley@temporal.io>

A resource method passed an optional parameter as it was and dropped the default of the field. A source is a helper value and never an argument, so it no longer fills an optional parameter.

A resource method hands an optional parameter to its operation, which applies the field's default. A source is a helper value and never an argument, so it no longer fills an optional parameter.

The stream sample's resource methods go through the options type, which applies the default. A source is a helper value and never an argument, so it no longer fills an optional parameter.

A default is an omittable argument, which the optional `producer` of `append` and `close` needs. The guide and the changelog describe the default rule for resource methods. Co-authored-by: Tim Conley <timothy.conley@temporal.io>

tconley1428 · 2026-11-13T18:26:49Z

This Doesn't make sense to me. That's what @nexus.default is for.

The import cycle fix landed on this branch while the default rework was built on the commit before it. The result is the tree that the checks ran on. Co-authored-by: Tim Conley <timothy.conley@temporal.io>

moetemp · 2026-11-13T18:42:10Z

I thought the same, and was working on it. Reworked it onto @nexus.default. A Python resource method ignored the field's default once it had the parameter, and that's the fix now.

tconley1428 and others added 30 commits November 5, 2026 11:01

fix(typescript): infer Long from protobuf resource bindings

1ea71f6

docs: shorten the generic resources section of the guide

3dd0887

test: assert the full message of each type parameter rejection

14dccae

docs: say why a generic handle keeps its runtime types

6df19ed

Co-authored-by: Tim Conley <timothy.conley@temporal.io>

feat: infer the type parameters of a resource

86d7a9f

A resource that uses a type parameter, also through its records, is generic in it, as a record is. So a resource needs no annotation, and `@nexus.type-parameter` is valid only on a type alias again.

fix(python): decode generic resources from their type arguments (#367)

820a03c

fix: infer resource type parameters from results in declaration order

3670d4f

Only a returned resource gives its type parameters, as the guide says, so a parameter or field that holds one doesn't. The declaration order doesn't change when a method moves.

fix: refuse a generic resource anywhere in a record field

37db1c1

A list, map, tuple, result or variant case builds the resource from the record's message too, so it gets no type argument either.

fix: say that a direct generic resource result isn't supported yet

72fbf80

The old reason said a proto message holds the type arguments, which it doesn't.

fix: refuse runtime type names that collide with each other or a method

b07e0c2

Two type parameters such as `body` and `body-t` give the same runtime type name, and a method can take it too. Either one makes a duplicate parameter or member.

fix(python): keep the runtime output type in the System Nexus dispatch

a978b24

The typed hook of a generic response took only the request, so the terminal decoded `ReadRecordsResponse[Turn]` with the plain class and lost `Turn`.

fix(dotnet): send generic System Nexus operations to the generic hook

17889c1

C# generics are invariant, so the `<object>` checks refused a `Stream<Turn>` call. The dispatch now compares generic type definitions and keeps the call's types.

fix(python): read the type argument of a subclassed generic handle

c61de1c

A subclass such as `class TurnStream(Stream[Turn])` has no `__orig_class__`, so the handle reads `__orig_bases__` too. A factory tests `body_type is None`, since a class can be falsy.

test: cover a typed TypeScript read and a bare Python handle class

f64662d

The TypeScript stream test now decodes a body with a runtime type. The Python test decodes to the bare handle class, since a generic alias fails for another reason.

chore: fold the generic resource changelog and describe the fixes

4c23348

No release has the Python constructor change, so it belongs with the added entry. The fixed entry now describes the System Nexus dispatch fixes.

docs: reword the generic resource comments and wrap long lines

b87266a

A few comments used "name" as a verb, ran over two lines or over 100 columns. The guide's first paragraph read as one long sentence.

chore: fold the generic resource changelog into one entry

4379aaa

chore: trim the generic resource tests and docs

15d3216

Drop the tests that repeat another test or restate generated code, and keep the ones that guard behavior. Shorten the guide section and the comments.

feat: close a resource at the end of async with

9de8ae5

`@nexus.close` marks the method that ends a resource. Python calls it at the end of `async with`, and a call that returns the resource returns a `ResourceCall`. Co-authored-by: Tim Conley <timothy.conley@temporal.io>

feat(python): add a Workflow resource factory

d2a1665

Workflow code gets a handle on an existing Stream with `get_stream[T]`, from the fields of its ref, with no call. Co-authored-by: Tim Conley <timothy.conley@temporal.io>

feat(python): add RPC options to client calls

2c81018

Each client call and client resource method takes `rpc_metadata` and `rpc_timeout`, and passes them to the `start_operation` of its Nexus client. Co-authored-by: Tim Conley <timothy.conley@temporal.io>

feat: limit @nexus.api-omit to some targets

01767a3

A field can leave the API of one target and take a source in another. A call of a target that omits a required list sends it empty. Co-authored-by: Tim Conley <timothy.conley@temporal.io>

Merged #358 into the combined base.

bd09703

Merged #369 into the combined base.

951ca1d

Merged #372 into the combined base.

4f1fce3

moetemp and others added 5 commits November 12, 2026 21:53

Said in the sample's Producer docs that a call can pass its own.

65db414

The docs of both `producer` fields match the API's WIT, which has the two optional parameters. Co-authored-by: Tim Conley <timothy.conley@temporal.io>

Merged the stream sample sync into the source fallback.

aa95910

The sync gave `append` its optional `sequence`, and this branch puts it after `producer` as the API's WIT does. The generated samples were rebuilt, not merged by hand.

Merged the stream sample sync into the source fallback.

433d981

The sync brings the API's new offset and Workflow Producer comments, which this branch also needs. Co-authored-by: Tim Conley <timothy.conley@temporal.io>

This was referenced Nov 13, 2026

feat: use a field's @nexus.source as the default of an optional method parameter moetemp/nexgen#114

Closed

Streams API: combined branch for review moetemp/sdk-python#381

Closed

moetemp and others added 5 commits November 13, 2026 10:04

Filled an unset optional parameter from its field's default in Python.

c64d2c0

A resource method passed an optional parameter as it was and dropped the default of the field. A source is a helper value and never an argument, so it no longer fills an optional parameter.

Took the source fallback out of TypeScript resource methods.

6c88155

A resource method hands an optional parameter to its operation, which applies the field's default. A source is a helper value and never an argument, so it no longer fills an optional parameter.

Took the source fallback out of .NET resource methods.

3a9d7d6

The stream sample's resource methods go through the options type, which applies the default. A source is a helper value and never an argument, so it no longer fills an optional parameter.

moetemp added this pull request to stack #411 November 13, 2026 18:26

Merged the default rework with the import cycle fix.

32139af

The import cycle fix landed on this branch while the default rework was built on the commit before it. The result is the tree that the checks ran on. Co-authored-by: Tim Conley <timothy.conley@temporal.io>

moetemp changed the title ~~feat: use a field's @nexus.source as the default of an optional method parameter~~ fix: apply a field's @nexus.default to an optional resource method parameter in Python Nov 13, 2026

moetemp added 2 commits November 13, 2026 11:40

Told why the stream sample offset comment matters.

06b177e

Merged the stream sample sync into the source fallback.

b0ffc6f

moetemp marked this pull request as ready for review November 13, 2026 18:46

moetemp requested a review from a team as a code owner November 13, 2026 18:46

tconley1428 approved these changes Nov 13, 2026

View reviewed changes

Base automatically changed from moe/up/stream-writer-sync-1106 to main November 13, 2026 18:51

Merged main into the source fallback.

d5003c2

moetemp enabled stacked auto-merge (squash) November 13, 2026 18:56

moetemp disabled stacked auto-merge November 13, 2026 18:56

moetemp enabled stacked auto-merge (squash) November 13, 2026 18:56

tconley1428 disabled stacked auto-merge November 13, 2026 19:03

tconley1428 merged commit 48c6973 into main Nov 13, 2026
5 checks passed

tconley1428 deleted the moe/up/source-fallback branch November 13, 2026 19:03

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fix: apply a field's `@nexus.default` to an optional resource method parameter in Python - #408

fix: apply a field's `@nexus.default` to an optional resource method parameter in Python#408
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