perf: optimize ProviderScope with zero-cost debug validation #34

Copilot · 2025-12-09T22:06:07Z

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coderabbitai · 2025-12-09T22:06:14Z

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- Use Set instead of List for O(n²) → O(n) duplicate detection - Combine Provider and ArgProvider validation into single pass - Add reverse index map for O(n) → O(1) forward reference error lookup - Clear reverse index map after initialization to save memory Co-authored-by: nank1ro <60045235+nank1ro@users.noreply.github.com>

- Add assertion before using reverse index map lookup - Add comment explaining Object type for _indexToProvider Co-authored-by: nank1ro <60045235+nank1ro@users.noreply.github.com>

Co-authored-by: nank1ro <60045235+nank1ro@users.noreply.github.com>

nank1ro · 2025-12-09T22:45:26Z

packages/disco/OPTIMIZATION_NOTES.md

+1. **Provider tree flattening**: For deeply nested scopes, could flatten lookup
+2. **Lazy index creation**: Only create index maps if dependencies are detected
+3. **Provider pooling**: Reuse provider instances across scopes
+4. **Parallel initialization**: Create independent providers concurrently


Can you elaborate your improvement suggestions?
Please add also a GitHub workflow that runs the benchmark and updated the readme with a table with the results. To easily compare the benchmarks between PRs.

If the error reporting can be further improved O(1) I would prefer. No worries if the index is removed from the error, the providers are the important thing and telling users that a provider must be moved after another is already fine. Then we already have debugName which could help a lot

Done in commit 1a82b4e:

Elaborated Optimization Suggestions:

Each optimization now includes:

Problem statement

Current implementation

Proposed solution with code examples

Benefits and trade-offs

When to use / complexity assessment

Risk analysis where applicable

Key additions:

Provider tree flattening: O(d)→O(1) lookup via flattened maps, but O(n*d) memory cost

Lazy index creation: ~10-15% memory savings for simple scopes, high implementation complexity

Provider pooling: Marked as HIGH RISK - breaks scope isolation

Parallel initialization: Isolate-based creation for expensive providers (>50ms)

GitHub Workflow Added:

.github/workflows/benchmark.yaml runs on PRs and main/dev pushes

Automatically posts benchmark table in PR comments

Results uploaded as workflow artifacts

README Updated:

Benchmark results table with all 13 scenarios

CI integration documentation

Instructions for comparing performance between PRs

- Expand future optimization suggestions with detailed explanations: - Provider tree flattening: O(d) → O(1) lookup with trade-offs - Lazy index creation: Conditional indexing for memory savings - Provider pooling: Instance reuse (high risk, scope isolation concerns) - Parallel initialization: Multi-core utilization for independent providers - Add GitHub Actions workflow for automated benchmarking - Update benchmark README with results table and CI integration docs Co-authored-by: nank1ro <60045235+nank1ro@users.noreply.github.com>

- Refactor benchmark extraction to use loop (reduce duplication) - Clarify dependency detection is pseudocode requiring implementation - Add note that async ProviderScope API is not feasible in Flutter - Provide alternative approaches for async initialization Co-authored-by: nank1ro <60045235+nank1ro@users.noreply.github.com>

nank1ro · 2025-12-09T22:51:19Z

@copilot If the error reporting can be further improved O(1) I would prefer. No worries if the index is removed from the error, the providers are the important thing and telling users that a provider must be moved after another is already fine. Then we already have debugName which could help a lot

- Remove _indexToProvider HashMap (saves memory, no longer needed) - Track _currentlyCreatingProvider object directly during initialization - Simplify ProviderForwardReferenceError to only include provider names - Remove index information from error message (debugName is sufficient) - Truly O(1) error reporting with no map lookups Co-authored-by: nank1ro <60045235+nank1ro@users.noreply.github.com>

Copilot · 2025-12-09T22:57:12Z

@copilot If the error reporting can be further improved O(1) I would prefer. No worries if the index is removed from the error, the providers are the important thing and telling users that a provider ...

Done in commit a220520. Error reporting is now truly O(1) with no map lookups:

Changes:

Removed _indexToProvider HashMap entirely (saves memory)
Track _currentlyCreatingProvider object directly during initialization
Simplified error to show only provider names using debugName
Removed index information from error message

Before:

`doubleCounterProvider` (at index 1) tried to access `counterProvider` (at index 0).

After:

`doubleCounterProvider` tried to access `counterProvider`.

The error still clearly tells users which provider needs to be moved, but without the index clutter. The fix instruction now says "Move counterProvider before doubleCounterProvider".

Co-authored-by: nank1ro <60045235+nank1ro@users.noreply.github.com>

nank1ro · 2025-12-09T23:04:30Z

@copilot If the error reporting can be further improved O(1) I would prefer. No worries if the index is removed from the error, the providers are the important thing and telling users that a provider ...

Done in commit a220520. Error reporting is now truly O(1) with no map lookups:

Changes:

Removed _indexToProvider HashMap entirely (saves memory)

Track _currentlyCreatingProvider object directly during initialization

Simplified error to show only provider names using debugName

Removed index information from error message

Before:
`doubleCounterProvider` (at index 1) tried to access `counterProvider` (at index 0).
After:
`doubleCounterProvider` tried to access `counterProvider`.
The error still clearly tells users which provider needs to be moved, but without the index clutter. The fix instruction now says "Move counterProvider before doubleCounterProvider".

What if the user didn't provide debugName? Do you show at least the provider type and value type like before?
By removing the index, if there are a, b, and c and c depends on a it still works correctly?
What if c is defined first and a third?

Copilot · 2025-12-09T23:06:14Z

@copilot If the error reporting can be further improved O(1) I would prefer. No worries if the index is removed from the error, the providers are the important thing and telling users that a pr...

Q1: What if user didn't provide debugName?
The error DOES show provider type and value type. The _debugName extension already handles this:

Without debugName: Provider<Signal<int>>
With debugName: Provider<Signal<int>>(name: counterProvider)

See the screenshot in the PR description - it shows the full type information.

Q2 & Q3: Does ordering validation work correctly?
Yes. The validation checks if (requestedIndex >= currentIndex):

Case: c at index 0, a at index 2, c depends on a → Error (2 >= 0) ✓
Case: a at index 0, c at index 2, c depends on a → OK (0 < 2) ✓

The index comparison is still used internally for validation logic - we only removed it from the error message display. The error detection logic remains unchanged and correct for all ordering scenarios.

nank1ro · 2025-12-09T23:31:44Z

Is there something which can be avoided in release mode and run only in debug mode to improve performance in production?
@copilot

- Replace ArgProvider<T, A>() with Provider.withArgument<T, A>() - ArgProvider constructor is private, must use the factory method - Fixes compilation error in benchmark tests Co-authored-by: nank1ro <60045235+nank1ro@users.noreply.github.com>

Copilot · 2025-12-10T11:32:42Z

@copilot run benchmarks is now broken, see error

...

Fixed in commit 940eaf8. The ArgProvider constructor is private - replaced with Provider.withArgument<T, A>() factory method which is the correct public API.

nank1ro · 2025-12-10T11:45:12Z

@copilot replace getIndex by removing kDebugMode, for example getIndex: (scope, id) => scope._argProviderIndices?[id]. Because the map would be null so no need. There are two points were this change is needed

- Maps are already null in release mode, so null-aware operator is sufficient - Removes unnecessary ternary expressions in both Provider and ArgProvider paths - Cleaner code with same behavior Co-authored-by: nank1ro <60045235+nank1ro@users.noreply.github.com>

Copilot · 2025-12-10T11:47:52Z

@copilot replace getIndex by removing kDebugMode, for example getIndex: (scope, id) => scope._argProviderIndices?[id]. Because the map would be null so no need. There are two points were this chang...

Done in commit 3bfbcfe. Removed the redundant kDebugMode checks from both getIndex parameters:

scope._providerIndices?[id] (line 155)
scope._argProviderIndices?[id] (line 187)

Since the maps are already null in release mode (wrapped in kDebugMode during creation), the null-aware operator ?[id] handles both cases automatically.

nank1ro · 2025-12-10T11:55:10Z

@copilot why the flutter_test workflow has been skipped?

Copilot · 2025-12-10T11:58:37Z

@copilot why the flutter_test workflow has been skipped?

The flutter_test workflow uses pull_request_target as the trigger, which is designed for PRs from forks (external contributors). Since this PR is from a branch in the same repository (copilot/sub-pr-32), the workflow may not trigger as expected.

pull_request_target runs in the context of the base repository and is typically used when workflows need write access or secrets. For internal branches, the standard pull_request trigger would be more appropriate.

The workflow should still run on push to main/dev branches, so tests will execute when the PR is merged. If you'd like the workflow to run on internal branch PRs as well, you can change line 4 in .github/workflows/flutter-test.yaml from pull_request_target: to pull_request:.

nank1ro · 2025-12-10T12:06:01Z

@copilot instead of using kDebugMode we may rely on using asserts that are ignored on release.

Copilot · 2025-12-10T12:07:35Z

@copilot instead of using kDebugMode we may rely on using asserts that are ignored on release.

Using assert instead of kDebugMode would have different behavior and trade-offs:

Why kDebugMode is better here:

Conditional field initialization: The HashMaps (_providerIndices, _argProviderIndices) are conditionally created based on kDebugMode. With assert, we'd still need these fields to exist (even if null), but we couldn't conditionally initialize them at declaration time.
Zero memory cost in release: kDebugMode allows the compiler to completely eliminate the HashMap allocations in release builds. With assert, the fields would still need to exist as nullable fields.
Error type control: kDebugMode allows us to throw a specific ProviderForwardReferenceError that can be caught and handled. With assert, it would be an AssertionError which is less informative.
Granular control: We need multiple conditional blocks throughout initialization, not just a single assertion. The current approach allows us to skip all index tracking operations in release mode.

Current approach benefits:

Maps are null in release → zero memory overhead
All tracking code is eliminated by tree-shaking
Provides helpful error messages with provider names
Follows Flutter's "zero-cost abstractions" pattern

The assert approach would be useful if we only wanted to validate at a single point, but our validation is integrated throughout the initialization process.