Output Formats

Output Formats

Every SPM command emits JSON Lines (JSONL): one self-contained JSON object per line. This page documents the schemas produced by analyze (static) and the instrumented app under run (runtime). Field names and types here are taken directly from the toJson methods in lib/src/features/*/data/models/. For the meaning of each analysis metric, see Extracted Features.

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Static analysis JSONL (analyze)

One JSON object per line, one line per State class. The analyze output contains exactly these 17 fields (AnalysisResultModel.toJson):

{
  "instanceId": "42",
  "filePath": "lib/screens/shopping_cart_screen.dart",
  "stateClassName": "_ShoppingCartScreenState",
  "treeNonConstWidgetCount": 24,
  "treeMaxWidgetNestingDepth": 7,
  "treeListRenderingStrategy": 2,
  "rootBuildReturnsConstWidget": 0,
  "treeConstWidgetCount": 2,
  "helperReferenceCount": 2,
  "usesLayoutDependentBuilder": 1,
  "treeCyclomaticComplexity": 5,
  "treeIterationCount": 1,
  "treeMaxIterationNestingDepth": 1,
  "iterationWidgetCount": 3,
  "valueObjectAllocCount": 4,
  "helperWidgetCount": 3,
  "helperMaxWidgetNestingDepth": 2
}

Field reference

Field	Type	Description
instanceId	string	ID for this State class: hash of the root-relative path + class name. Used to join with runtime profiler data. It is not unique across transplanted targets that share one file/class, so the benchmark pipeline keys by sample_id instead.
filePath	string	Source path relative to the analyzed project root.
stateClassName	string	Name of the State subclass.
treeNonConstWidgetCount	int	Non-const widget instantiations across reachable build bodies; excludes const boundaries and helper-body widgets.
treeMaxWidgetNestingDepth	int	Maximum widget depth composed across reachable custom-widget build bodies.
treeListRenderingStrategy	0/1/2	Worst list-rendering form across builds and helpers: 0 none, 1 lazy (.builder/.separated/.custom, slivers), 2 eager O(N) (concrete children: on a scroll list, or runtime-length Column/Row/Wrap/Flex children). (Replaced the buildUsesListViewBuilder boolean on 2026-07-20.)
rootBuildReturnsConstWidget	0/1	Whether the root State.build directly returns a const widget.
treeConstWidgetCount	int	Const widget boundaries across reachable build bodies; helper-body const widgets belong to helperWidgetCount. (Named constConstructorRatio in JSONL produced before 2026-07-18.)
helperReferenceCount	int	Widget-returning helper reference sites in reachable build bodies: invocations, tear-offs, and explicit getters.
usesLayoutDependentBuilder	0/1	Whether builds or helpers use LayoutBuilder, CustomMultiChildLayout, or Flow.
treeCyclomaticComplexity	int	Complexity summed across reachable build bodies, plus helper-body decision points without extra helper base points.
treeIterationCount	int	Loops, collection-for elements, and linear collection operations across build and helper bodies.
treeMaxIterationNestingDepth	int	Maximum lexical iteration nesting within any analyzed build or helper body.
iterationWidgetCount	int	Non-const widgets built in per-element scopes across builds and helpers: loops, collection-op callbacks, and lazy builders.
valueObjectAllocCount	int	All non-const, non-widget constructor allocations across build and helper bodies.
helperWidgetCount	int	Widget instantiations in reachable helper bodies, including const widgets.
helperMaxWidgetNestingDepth	int	Maximum widget nesting within any individual reachable helper body.

0/1 fields are Dart bools serialized as 1/0 by toJson. See Extracted Features for the precise definition of each metric.

Key migration (2026-07-20 rename)

Feature keys were renamed so every name states its scope: tree* = aggregated over the whole static call tree, root* = root build() only, helper* = helper bodies only. Older JSONL files can be normalized with this map:

Old key (pre-2026-07-20)	Current key
buildWidgetInstanceCount	treeNonConstWidgetCount
buildMaxWidgetNestingDepth	treeMaxWidgetNestingDepth
buildUsesListViewBuilder (bool, pre-07-20) / buildListRenderingStrategy	treeListRenderingStrategy
buildReturnsConstWidget	rootBuildReturnsConstWidget
constConstructorRatio (pre-07-18) / constWidgetCount	treeConstWidgetCount
buildHelperMethodCount	helperReferenceCount
buildCyclomaticComplexity	treeCyclomaticComplexity
buildIterationCount	treeIterationCount
buildMaxIterationNestingDepth	treeMaxIterationNestingDepth
helperMethodWidgetCount	helperWidgetCount
helperMethodMaxNestingDepth	helperMaxWidgetNestingDepth

usesLayoutDependentBuilder, iterationWidgetCount, valueObjectAllocCount, and the identity keys (instanceId, filePath, stateClassName) are unchanged. The legacy boolean buildUsesListViewBuilder maps onto the none/lazy levels of the ordinal only; it cannot express eager (2).

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Runtime profiler JSONL (run / instrumented app)

Two event types are emitted, distinguished by the event field. Which one you get depends on the Flutter build mode (see inject): --profile → performance_metric, --debug → dataflow-metric. Every event carries a timestamp (ISO-8601) and the instanceId that joins back to the static-analysis record.

Performance event, emitted under --profile (PerformanceMetricsModel.toJson):

{
  "timestamp": "2026-02-20T10:15:30.123Z",
  "event": "performance_metric",
  "instanceId": "42",
  "buildSpan": 4123
}

Field	Type	Description
timestamp	string	ISO-8601 timestamp of the event.
event	string	Always "performance_metric".
instanceId	string	The instrumented State instance.
buildSpan	int	Build duration of the matched rebuild frame, in microseconds (0 on the 5-second timeout fallback).

Dataflow event, emitted under --debug (DataflowMetricsModel.toJson):

{
  "timestamp": "2026-02-20T10:15:30.456Z",
  "event": "dataflow-metric",
  "instanceId": "42",
  "taintedRebuildCount": 5,
  "totalWidgetCount": 42,
  "maxNestingDepth": 7,
  "taintedRatio": 0.119,
  "opacityRebuildCount": 0,
  "shaderMaskRebuildCount": 0,
  "clipRRectRebuildCount": 1,
  "clipOvalRebuildCount": 0,
  "clipPathRebuildCount": 0,
  "backdropFilterRebuildCount": 0
}

Field	Type	Description
timestamp	string	ISO-8601 timestamp of the event.
event	string	Always "dataflow-metric".
instanceId	string	The instrumented State instance.
taintedRebuildCount	int	Widgets that actually rebuilt as a result of the setState.
totalWidgetCount	int	Total widgets in the analyzed subtree.
maxNestingDepth	int	Maximum nesting depth of the analyzed subtree.
taintedRatio	double	taintedRebuildCount / totalWidgetCount.
opacityRebuildCount	int	Rebuilt Opacity widgets.
shaderMaskRebuildCount	int	Rebuilt ShaderMask widgets.
clipRRectRebuildCount	int	Rebuilt ClipRRect widgets.
clipOvalRebuildCount	int	Rebuilt ClipOval widgets.
clipPathRebuildCount	int	Rebuilt ClipPath widgets.
backdropFilterRebuildCount	int	Rebuilt BackdropFilter widgets.