Files
app/backend/fluksio/sdk/__init__.py
T
stroblmeandClaude Opus 5 81649dbfca Refuse a __main__ node where its body is written, not at import
A module defining nodes could not be run directly: the decorator refused
`__main__` while the module body was still executing, so a `if __name__ ==
"__main__"` self-check beside the nodes was impossible and the checks had
to live in a separate pytest file. The refusal now fires where the
generated body is written — document() and shims(), both, since sync writes
the document first — and the decorator hands the function back as it always
did. Syncing a __main__-defined node is still refused, with the same words.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_019Hra4ndWMCLU5F3KjUuVAc
2026-08-29 13:50:35 +02:00

816 lines
30 KiB
Python

"""Declare flows and nodes in the repository you already have.
A research repository keeps its functions where they are; the decorators here
say which of them are nodes and which nodes make up a flow. ``fluksio sync``
uploads the flow document and, per node, a generated import shim — so the flow
store still holds a complete, runnable, git-versioned definition, and the code
it imports stays yours.
Nothing here imports the engine. A ``from fluksio import node`` in a training
script must not drag FastAPI and SQLAlchemy in behind it, and the same names
have to resolve inside a worker, where ``fluksio`` is the reporter module.
"""
from __future__ import annotations
import ast
import inspect
import json
import re
import textwrap
import warnings
from collections.abc import Callable, Sequence
from pathlib import Path
from typing import Any, TypeVar
from fluksio.sdk.imports import digest_of, reached
__all__ = [
"FLOWS",
"Flow",
"Port",
"SyncError",
"build",
"node",
"shims",
"use",
]
F = TypeVar("F", bound=Callable[..., Any])
#: Mirrors :class:`fluksio.flow.messages.DType`. Mirrored rather than imported:
#: importing it would pull the engine into a research process.
DTYPES = frozenset(
{
"float",
"int",
"str",
"bool",
"json",
"series",
"record",
"list",
"artifact",
"image",
"audio",
"video",
}
)
#: What a list may hold, mirroring ``messages._ITEM_TYPES``.
ITEM_TYPES = frozenset({"float", "int", "str", "bool", "json", "record"})
#: Settings the engine reads itself, mirroring ``nodes.base.RESERVED_SETTINGS``.
RESERVED_SETTINGS = frozenset({"synchronous"})
#: Mirrors ``fluksio.flow.schemas.NAME_PATTERN``.
NAME_PATTERN = re.compile(r"^[a-z][a-z0-9_]*$")
#: First line of every generated node body. Its absence is how ``sync`` knows a
#: node's source was edited on the canvas.
MARKER = "# generated by fluksio sync"
class SyncError(Exception):
"""A declaration the engine would refuse, caught where it was written."""
#: Every flow declared in the modules imported so far. ``fluksio sync`` reads it.
FLOWS: dict[str, Flow] = {}
def _name(value: str, what: str) -> str:
if not NAME_PATTERN.match(value):
raise SyncError(
f"{what} '{value}': use lowercase letters, digits and underscores, "
"starting with a letter"
)
return value
class Port:
"""One port of a node, and the message it binds to.
A thin mirror of :class:`fluksio.flow.messages.MessageSpec`. ``name`` is
the wiring — two nodes are connected because one provides the name another
requires — and ``port`` is what the function calls its parameter, which
defaults to the name.
"""
def __init__(
self,
name: str,
dtype: str | None = None,
*,
port: str = "",
stream: bool = False,
initial: Any = None,
item: str | None = None,
interval: float = 0.0,
trigger: bool = True,
) -> None:
#: Whether the caller said the type or left it to be resolved from
#: whoever provides the message. A message has one type, declared where
#: it is produced; requiring it does not mean declaring it again.
self.explicit = dtype is not None
dtype = dtype or "float"
if dtype not in DTYPES:
raise SyncError(f"port '{name}': unknown type '{dtype}'")
if item is not None and item not in ITEM_TYPES:
raise SyncError(f"port '{name}': a list cannot hold '{item}' items")
if interval < 0:
raise SyncError(f"port '{name}': interval cannot be negative")
self.name = name
self.dtype = dtype
self.port = port or name.rsplit(".", 1)[-1]
self.stream = stream
self.initial = initial
self.item = item
self.interval = interval
self.trigger = trigger
if not self.port.isidentifier():
raise SyncError(
f"port '{name}': '{self.port}' is not a Python identifier, so no "
"parameter can carry it — pass port='...'"
)
def spec(self) -> dict[str, Any]:
"""The ``MessageSpec`` this port serialises to."""
out: dict[str, Any] = {
"name": self.name,
"port": self.port,
"dtype": self.dtype,
"interval": self.interval,
"trigger": self.trigger,
"stream": self.stream,
}
if self.item is not None:
out["item"] = self.item
return out
def replace(self, name: str = "") -> Port:
"""A copy of this port, optionally bound to a different message."""
copy = Port(
name or self.name,
self.dtype,
port=self.port,
stream=self.stream,
initial=self.initial,
item=self.item,
interval=self.interval,
trigger=self.trigger,
)
copy.explicit = self.explicit
return copy
def __repr__(self) -> str:
return f"Port({self.name!r}, {self.dtype!r})"
def _ports(value: Sequence[str | Port] | str | Port) -> tuple[list[Port], bool]:
"""Normalise a ports declaration; the flag says it was a single port.
A single ``Port`` rather than a list of one is the opt-in to a bare return:
the shim wraps the value in the dict the engine expects. It has to be
explicit, because an artifact reference is itself a dict and a dict whose
keys match no port is dropped in silence.
"""
if isinstance(value, (str, Port)):
return [value if isinstance(value, Port) else Port(value)], True
return [item if isinstance(item, Port) else Port(item) for item in value], False
class NodeSpec:
"""What ``@node`` recorded about a function."""
def __init__(
self,
fn: Callable[..., Any],
*,
id: str,
requires: list[Port],
provides: list[Port],
single: bool,
settings: dict[str, Any],
title: str,
timeout: float | None,
device: str | None,
device_policy: str,
cache: bool = True,
resources: dict[str, Any] | None = None,
) -> None:
self.fn = fn
self.id = id
self.requires = requires
self.provides = provides
self.single = single
self.settings = settings
self.title = title
self.timeout = timeout
self.device = device
self.device_policy = device_policy
self.cache = cache
self.resources = resources
def rebind(
self, *, id: str = "", wire: dict[str, str] | None = None, **settings: Any
) -> NodeSpec:
"""A copy of this node wired and configured for one flow."""
wire = wire or {}
known = {port.port for port in self.requires} | {p.port for p in self.provides}
unknown = sorted(set(wire) - known)
if unknown:
raise SyncError(
f"node '{self.id}': wire={{'{unknown[0]}': ...}} names no port of it "
f"(it has {', '.join(sorted(known)) or 'none'})"
)
# Copied rather than shared: the same decorated function appears in
# several flows, and each resolves its own port types.
def rewire(ports: list[Port]) -> list[Port]:
return [port.replace(wire.get(port.port, "")) for port in ports]
return NodeSpec(
self.fn,
id=_name(id, "node id") if id else self.id,
requires=rewire(self.requires),
provides=rewire(self.provides),
single=self.single,
settings={**self.settings, **settings},
title=self.title,
timeout=self.timeout,
device=self.device,
device_policy=self.device_policy,
cache=self.cache,
resources=self.resources,
)
class NodeUse:
"""One use of a decorated function in one flow — see :func:`use`."""
def __init__(
self,
fn: Callable[..., Any],
*,
id: str = "",
wire: dict[str, str] | None = None,
settings: dict[str, Any] | None = None,
) -> None:
self.fn = fn
self.id = id
self.wire = wire
self.settings = settings or {}
def node(
*,
requires: Sequence[str | Port] = (),
provides: Sequence[str | Port] | str | Port = (),
id: str = "",
settings: dict[str, Any] | None = None,
title: str = "",
timeout: float | None = None,
device: str | None = None,
device_policy: str = "require",
cache: bool = True,
resources: dict[str, Any] | str | None = None,
) -> Callable[[F], F]:
"""Mark a function as a node, declaring its ports.
The function is returned untouched: it is still callable, testable and
importable as what it was. A bare string in ``requires`` or ``provides`` is
shorthand for a ``float`` port of that name.
Parameters with a default that are not ports become the node's settings, so
the canvas can tune them without editing code. ``device`` picks the worker
the code runs on — ``"gpu"``, say — and ``device_policy="prefer"`` runs it
locally when no such worker is attached rather than waiting for one.
A batch run skips this node when an earlier one already ran the same source
with the same settings and the same input values, and restores what it
returned. ``cache=False`` says not to: the answer can change on its own.
``timeout`` is seconds of silence — a yield or an emit resets it — after
which the node is stopped. Left out it inherits the engine's default, which
is no limit; set one where silence means stuck rather than working.
``resources`` says how much of the machine one execution takes, for a node
heavy enough that the answer is not "a share of it"::
@node(..., resources={"cpus": 4})
@node(..., resources={"gpus": 1,
"env": {"XLA_PYTHON_CLIENT_MEM_FRACTION": "0.9"}})
The engine holds that much while the node runs, so the rest of them wait
their turn rather than oversubscribing the box, and the worker is started
with thread limits matching what it was given — which is the only way a
library that sizes itself to every visible core is told otherwise. ``env``
is for the tuning the engine must not invent, such as ``XLA_FLAGS``.
Declaring nothing is the default and changes nothing.
A string is a stored flavor — ``resources="gpu-small"`` — which is the same
thing as ``{"flavor": "gpu-small"}`` and stands in for cpus, gpus and ram.
Sizes accept ``"2G"``; ``duration_s`` accepts ``"30m"``.
"""
if device_policy not in ("require", "prefer"):
raise SyncError("device_policy is 'require' or 'prefer'")
if isinstance(resources, str):
resources = {"flavor": resources}
if resources is not None:
known = {"cpus", "gpus", "ram", "flavor", "duration_s", "env"}
unknown = sorted(set(resources) - known)
if unknown:
raise SyncError(
f"resources={{'{unknown[0]}': ...}} is not one of "
f"{', '.join(sorted(known))}"
)
if timeout is not None and timeout < 0:
raise SyncError(
f"node timeout must be 0 or more (0 disables it), got {timeout}"
)
def decorate(fn: F) -> F:
required, _ = _ports(requires)
provided, single = _ports(provides)
spec = NodeSpec(
fn,
id=_name(id or fn.__name__, "node id"),
requires=required,
provides=provided,
single=single,
settings=dict(settings or {}),
title=title,
timeout=timeout,
device=device,
device_policy=device_policy,
cache=cache,
resources=dict(resources) if resources is not None else None,
)
_check_signature(spec)
fn.__fluksio__ = spec # type: ignore[attr-defined]
return fn
return decorate
def use(
fn: Callable[..., Any],
*,
id: str = "",
wire: dict[str, str] | None = None,
**settings: Any,
) -> NodeUse:
"""The same node, wired or configured differently in this flow.
``wire={"dataset": "augmented"}`` binds the ``dataset`` port to another
message; keyword arguments override settings. Give ``id`` when one function
appears twice in one flow.
"""
return NodeUse(fn, id=id, wire=wire, settings=settings)
def _spec_of(entry: Callable[..., Any] | NodeUse) -> NodeSpec:
fn = entry.fn if isinstance(entry, NodeUse) else entry
spec = getattr(fn, "__fluksio__", None)
if not isinstance(spec, NodeSpec):
raise SyncError(
f"{getattr(fn, '__name__', fn)!r} is not a node — decorate it with @node()"
)
if isinstance(entry, NodeUse):
return spec.rebind(id=entry.id, wire=entry.wire, **entry.settings)
return spec.rebind()
def _check_signature(spec: NodeSpec) -> None:
"""Whether the declaration matches the function it is on.
Raised where the decorator is rather than where the flow is: this is a
disagreement between a function and its own ports, and the engine would
otherwise only find it when the node is first called.
"""
fn, where = spec.fn, f"node '{spec.id}'"
if inspect.iscoroutinefunction(fn):
raise SyncError(f"{where}: async functions cannot be nodes")
generator = inspect.isgeneratorfunction(fn)
if generator and spec.single:
raise SyncError(
f"{where}: {fn.__name__}() yields, so it says which port each value is "
f"on — pass provides=[Port(...)] rather than a single port"
)
signature = inspect.signature(fn)
parameters = signature.parameters
var_keyword = any(
p.kind is inspect.Parameter.VAR_KEYWORD for p in parameters.values()
)
ports = {port.port for port in spec.requires}
for port in ports:
if port not in parameters and not var_keyword:
raise SyncError(
f"{where}: port '{port}' has no parameter to arrive in — "
f"{fn.__name__}({', '.join(parameters)}) takes no such argument"
)
for name, parameter in parameters.items():
if parameter.kind is inspect.Parameter.VAR_POSITIONAL:
raise SyncError(f"{where}: *{name} cannot be filled from ports")
if parameter.kind is inspect.Parameter.VAR_KEYWORD or name in ports:
continue
if parameter.default is inspect.Parameter.empty:
raise SyncError(
f"{where}: parameter '{name}' is neither a port nor a setting — "
f"add Port('{name}', ...) to requires=, or give it a default"
)
_check_emissions(spec)
def _check_emissions(spec: NodeSpec) -> None:
"""Whether what the function yields is what it says it provides.
The engine refuses an undeclared key at the first yield, which is right but
late: a sweep can be an hour in. Only literal keys are read here — a yield
of a name the code computes is left to the engine — so this catches the
mistake it is for, which is a typo.
"""
provided = {port.port for port in spec.provides}
try:
tree = ast.parse(textwrap.dedent(inspect.getsource(spec.fn)))
except (OSError, TypeError, SyntaxError):
# No source to read: a function built at runtime, or one from a
# console. Not a reason to refuse it.
return
for key in _emitted_keys(tree):
if key not in provided:
declared = ", ".join(sorted(provided)) or "none"
raise SyncError(
f"node '{spec.id}': {spec.fn.__name__}() emits '{key}', which no "
f"port declares. Its ports are: {declared}."
)
def _emitted_keys(tree: ast.AST) -> list[str]:
"""Literal port names a function yields or emits, its own only.
A nested function is somebody else's ports — a helper generator yielding
pairs is not this node emitting them — so the walk stops at one.
"""
keys: list[str] = []
# Each branch carries whether it is already inside the node's own function,
# so the first def is the node and any def below it is a helper.
stack: list[tuple[ast.AST, bool]] = [(tree, False)]
while stack:
node, inside = stack.pop()
if isinstance(node, (ast.FunctionDef, ast.AsyncFunctionDef, ast.Lambda)):
if inside:
continue
inside = True
if isinstance(node, ast.Yield) and isinstance(node.value, ast.Dict):
keys += [
key.value
for key in node.value.keys
if isinstance(key, ast.Constant) and isinstance(key.value, str)
]
elif isinstance(node, ast.Call) and _is_emit(node.func):
keys += [kw.arg for kw in node.keywords if kw.arg]
stack += [(child, inside) for child in ast.iter_child_nodes(node)]
return keys
def _is_emit(func: ast.expr) -> bool:
"""``emit(...)`` or ``fluksio.emit(...)``, however it was imported."""
if isinstance(func, ast.Name):
return func.id == "emit"
return isinstance(func, ast.Attribute) and func.attr == "emit"
def _check(spec: NodeSpec, mode: str) -> dict[str, Any]:
"""The node as stored, with the settings and wiring of one flow.
Mirrors ``FlowController._build_node`` and ``flow.runs.batch_issues``. Kept
apart from the signature check because ``use(fn, epochs=3)`` adds settings
per flow, so this is the first point at which they are all known.
"""
fn, where = spec.fn, f"node '{spec.id}'"
parameters = inspect.signature(fn).parameters
var_keyword = any(
p.kind is inspect.Parameter.VAR_KEYWORD for p in parameters.values()
)
ports = {port.port for port in spec.requires}
params: dict[str, Any] = {}
for name, parameter in parameters.items():
if name in ports or parameter.default is inspect.Parameter.empty:
continue
if name in RESERVED_SETTINGS:
continue
if _serialisable(parameter.default):
params[name] = parameter.default
for name, value in spec.settings.items():
if name in ports:
raise SyncError(
f"{where}: '{name}' is both a port and a setting — a node reads its "
"settings beside its ports, so the names have to differ"
)
if name in RESERVED_SETTINGS:
raise SyncError(f"{where}: '{name}' is a setting the engine reads itself")
if name not in parameters and not var_keyword:
raise SyncError(
f"{where}: setting '{name}' is not a parameter of {fn.__name__}()"
)
if not _serialisable(value):
raise SyncError(
f"{where}: setting '{name}' is not JSON — settings are stored with "
"the flow, so they have to survive a round trip"
)
params[name] = value
if mode == "batch":
for port in spec.requires + spec.provides:
if port.interval > 0 and not port.stream:
raise SyncError(
f"{where}: port '{port.port}' has interval={port.interval} but a "
"batch run delivers once — drop it, or declare stream=True"
)
return {
"id": spec.id,
"type": "python",
"title": spec.title,
"params": params,
"requires": [port.spec() for port in spec.requires],
"provides": [port.spec() for port in spec.provides],
"timeout": spec.timeout,
"device": spec.device,
"device_policy": spec.device_policy,
"cache": spec.cache,
"resources": spec.resources,
}
def _refuse_main(spec: NodeSpec) -> None:
"""A node the generated body would have no way to import.
Refused where the body is written rather than where the decorator is: a
module defining nodes is then still runnable as a script, which is what a
`__main__` self-check beside them needs.
"""
if spec.fn.__module__ == "__main__":
raise SyncError(
f"node '{spec.id}': {spec.fn.__name__}() is defined in a script run "
"directly, so the generated node could not import it — put it in an "
"importable module"
)
def _code_of(spec: NodeSpec) -> dict[str, Any]:
"""What this node's function calls into, which its shim does not say.
Read here rather than when the flow is declared, so a second `sync()` in
one process — a notebook — sees the edit that happened between them. This
side is the only one that can work it out at all: it has imported the
code, and the engine never does.
"""
_refuse_main(spec)
files = reached(spec.fn)
return {"code_files": files, "code_digest": digest_of(files)}
def _serialisable(value: Any) -> bool:
try:
json.dumps(value)
except (TypeError, ValueError):
return False
return True
class Flow:
"""A flow: which nodes are in it, what it takes and what it reports."""
def __init__(
self,
name: str,
*,
nodes: Sequence[Callable[..., Any] | NodeUse],
mode: str = "batch",
inputs: Sequence[Port] = (),
outputs: Sequence[str] = (),
title: str = "",
) -> None:
"""Declare a flow over decorated functions, and register it for sync.
``nodes`` is the membership: any decorated function, from anywhere in
the repository. Wiring is not membership — nodes connect because one
provides a message another requires, never because one imported the
other. Wrap an entry in :func:`use` to rebind or reconfigure it here
without touching the other flows using it.
"""
if mode not in ("batch", "live"):
raise SyncError(f"flow '{name}': mode is 'batch' or 'live'")
self.name = _name(name, "flow name")
self.title = title
self.mode = mode
self.inputs = list(inputs)
self.outputs = list(outputs)
self.nodes = [_spec_of(entry) for entry in nodes]
self._resolve_types()
self._validate()
self._nodes = [_check(spec, mode) for spec in self.nodes]
self._register()
def _register(self) -> None:
"""Put this flow where `fluksio sync` will find it."""
existing = FLOWS.get(self.name)
if existing is not None and existing is not self:
warnings.warn(
f"two flows are called '{self.name}'; the later one wins, and only "
"it will be synced",
stacklevel=3,
)
FLOWS[self.name] = self
def _resolve_types(self) -> None:
"""Give every required port the type of the message it reads.
A message has one type, declared once by whoever produces it. Requiring
it is not a second declaration, so `requires=["dataset"]` takes the
artifact type from the node providing `dataset` rather than defaulting
to a float the engine would then refuse at run time. Spelling the type
out on both sides is still allowed — and a disagreement is an error,
because one of the two is wrong about what it is handling.
"""
declared: dict[str, Port] = {}
for port in self.inputs:
declared.setdefault(port.name, port)
for spec in self.nodes:
for port in spec.provides:
declared.setdefault(port.name, port)
for spec in self.nodes:
for port in spec.requires:
source = declared.get(port.name)
if source is None:
continue
if not port.explicit:
port.dtype = source.dtype
port.item = source.item
elif port.dtype != source.dtype:
raise SyncError(
f"flow '{self.name}': node '{spec.id}' reads '{port.name}' as "
f"{port.dtype}, but it is provided as {source.dtype}"
)
def _validate(self) -> None:
seen: set[str] = set()
for spec in self.nodes:
if spec.id in seen:
raise SyncError(
f"flow '{self.name}': two nodes are called '{spec.id}' — "
"pass use(fn, id='...') to tell them apart"
)
seen.add(spec.id)
produced: dict[str, list[str]] = {}
for spec in self.nodes:
for port in spec.provides:
produced.setdefault(port.name, []).append(spec.id)
for name, writers in produced.items():
if len(writers) > 1:
warnings.warn(
f"flow '{self.name}': {', '.join(writers)} all publish "
f"'{name}', so a reader gets whichever ran last",
stacklevel=4,
)
available = set(produced) | {port.name for port in self.inputs}
for spec in self.nodes:
for port in spec.requires:
if "." in port.name or port.name in available:
continue
raise SyncError(
f"flow '{self.name}': node '{spec.id}' requires '{port.name}', "
"which no node in it provides and no input declares"
)
for output in self.outputs:
if output not in available:
raise SyncError(
f"flow '{self.name}': output '{output}' is not produced by any "
"of its nodes"
)
def document(self, origin: dict[str, Any] | None = None) -> dict[str, Any]:
"""The flow document to store, without a version — sync sets that."""
doc: dict[str, Any] = {
"name": self.name,
"title": self.title,
"mode": self.mode,
"nodes": [
node | _code_of(spec)
for spec, node in zip(self.nodes, self._nodes, strict=True)
],
"inputs": [
{"spec": port.spec(), "initial": port.initial} for port in self.inputs
],
"outputs": self.outputs,
}
if origin is not None:
doc["origin"] = origin
return doc
def shims(self) -> dict[str, str]:
"""One generated node body per node, keyed by node id."""
return {spec.id: _shim(spec) for spec in self.nodes}
def submit(
self, *, seed: int | None = None, client: Any = None, **params: Any
) -> Any:
"""Start a run of this flow and hand back a handle to it."""
from fluksio.sdk.client import Client
return (client or Client()).submit(self.name, params, seed=seed)
def runs(self, limit: int = 20, client: Any = None) -> list[dict[str, Any]]:
"""This flow's runs, newest first."""
from fluksio.sdk.client import Client
rows: list[dict[str, Any]] = (client or Client()).runs(
flow=self.name, limit=limit
)
return rows
def __repr__(self) -> str:
return f"Flow({self.name!r}, nodes={[n.id for n in self.nodes]})"
def build(target: Flow, origin: dict[str, Any] | None = None) -> dict[str, Any]:
"""The flow document for a flow — checked, without a version."""
return target.document(origin)
def shims(target: Flow) -> dict[str, str]:
"""The generated node bodies for a flow."""
return target.shims()
def import_root(fn: Callable[..., Any]) -> str:
"""The directory that has to be on the path for ``fn`` to be importable.
Its module's dotted name says how deep in a package it sits, so counting
the segments back up from the file lands on the directory the import
resolves against — which is not always the repository root, and is what a
generated shim actually needs.
"""
source = inspect.getsourcefile(fn)
if not source:
return ""
path = Path(source).resolve()
for _ in fn.__module__.split("."):
path = path.parent
return str(path)
def _shim(spec: NodeSpec) -> str:
"""The node body the store keeps: an import of the real function.
The store therefore still holds a complete, runnable definition — the body
simply happens to be generated, which is why it says so and says where the
real thing is.
"""
_refuse_main(spec)
fn = spec.fn
where = inspect.getsourcefile(fn) or fn.__module__
repo = import_root(fn)
ports = [port.port for port in spec.requires]
signature = ", ".join(ports + ["**settings"])
arguments = ", ".join([f"{port}={port}" for port in ports] + ["**settings"])
call = f"{fn.__name__}({arguments})"
lines = [
f"{MARKER} from {where} — edit that file instead",
"import sys",
"",
]
if repo:
# ponytail: the repository is on the path because the shim puts it
# there. An editable install (`-e /repo` in the Modules manifest, or a
# VCS requirement on a remote worker) makes these three lines a no-op.
lines += [
f"_REPO = {repo!r}",
"if _REPO not in sys.path:",
" sys.path.insert(0, _REPO)",
"",
]
lines += [
f"from {fn.__module__} import {fn.__name__}",
"",
"",
f"def process({signature}):",
]
if inspect.isgeneratorfunction(fn):
# `return (yield from ...)`, not a bare `yield from`: the delegating
# form is what carries the generator's own return value out, and that
# return value is everything the node produces at the end.
lines.append(f" return (yield from {call})")
elif spec.single:
lines.append(f" return {{{spec.provides[0].port!r}: {call}}}")
else:
lines.append(f" return {call}")
return "\n".join(lines) + "\n"