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feat(dynamic-views): unified branch foundations (types & parser)#2333

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Jrakru wants to merge 4 commits into
likec4:mainfrom
Jrakru:feat/unified-branch-foundations-clean
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feat(dynamic-views): unified branch foundations (types & parser)#2333
Jrakru wants to merge 4 commits into
likec4:mainfrom
Jrakru:feat/unified-branch-foundations-clean

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@Jrakru

@Jrakru Jrakru commented Oct 24, 2025

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Rationale

Dynamic views currently support only anonymous parallel steps with limited expressiveness. Users cannot:

  • Name or describe different execution paths
  • Model alternate/conditional flows (success vs error paths)
  • Provide contextual information for different branches
  • Support complex scenarios like retry logic or fallback paths

This PR establishes the type system and parser foundations for a unified branch abstraction that will eventually support both parallel AND alternate execution paths in dynamic views, enabling richer scenario modeling.

What This Changes

Type System (packages/core)

  • Add DynamicBranchCollection union type (parallel | alternate)
  • Add DynamicBranchPath for named, described execution paths
  • Add DynamicParallelBranch with legacy __parallel compatibility
  • Add DynamicAlternateBranch for conditional flows
  • Add type guards: isDynamicBranchCollection, isDynamicBranchPath
  • Add toLegacyParallel() helper for backward compatibility
  • Add feature flag system with dynamicBranchCollections (defaults: OFF)

Grammar & Parser (packages/language-server)

  • Extend Langium grammar with DynamicViewBranchCollection
  • Support syntax: parallel/par/alternate/alt { path name { steps } }
  • Parse anonymous steps into legacy __parallel format
  • Emit unified branch nodes with metadata for future stages
  • Update formatter to handle new branch syntax

Tests

  • Add type guard tests (packages/core/src/types/__tests__/dynamic-branch.spec.ts)
  • Add parser tests for named paths, alternate branches, chained steps
  • All existing tests pass (679 tests, backward compatible)

Code Quality

This PR has been reviewed by GitHub Copilot and addresses all actionable feedback:

Refactoring Applied:

  • Extracted getBranchKind() helper function for maintainability
  • Simplified nested ternary with clear if/else blocks
  • Removed unsafe type casts using proper type guards
  • Added documentation for dual environment variable support
  • Added JSDoc for toLegacyParallel() function
  • Improved isDynamicStep() boolean logic clarity

Backward Compatibility

  • ✅ Feature flag defaults to OFF (no behavior changes)
  • ✅ Legacy anonymous parallel syntax continues to work
  • ✅ Parser converts old syntax to new internal structures via __parallel
  • toLegacyParallel() helper maintains compute compatibility

Future Work

This unlocks:

  • PR02: Compute traversal for branch collections
  • PR03: Sequence diagram layout for branches
  • PR04: Walkthrough UI with branch navigation
  • PR05: UI polish for branch selection experience

Technical Notes

  • ✅ No changes to compute logic (deferred to PR02)
  • ✅ No UI changes (deferred to PR04/PR05)
  • ✅ Type-safe implementation (all TypeScript checks pass)
  • ✅ Comprehensive test coverage for new types and parser logic

Quality Gates

  • ✅ All tests pass (679 core tests + 609 language-server tests)
  • ✅ TypeScript compilation passes
  • ✅ Feature flag defaults to OFF
  • ✅ Backward compatible with existing dynamic views
  • ✅ Clean commit history (squashed feature + refactoring)

Related: This is the foundational PR for the unified branch system outlined in #2282. This PR focuses on types and parser only, with subsequent PRs handling compute, layout, and UI.

Introduces foundational types and grammar for parallel and alternate branch paths in dynamic views.

New Types:
- DynamicBranchCollection: Union of parallel/alternate branches
- DynamicBranchPath: Named or anonymous execution paths
- DynamicParallelBranch: Concurrent execution paths
- DynamicAlternateBranch: Mutually exclusive paths

Grammar Updates:
- DynamicViewBranchCollection: parallel|par|alternate|alt keywords
- DynamicViewBranchPath: Named paths with optional titles
- Backward compatible via feature flag (defaults OFF)

Changes:
- Add feature flag system (LIKEC4_UNIFIED_BRANCHES)
- Add type guards and helpers (isDynamicBranchCollection, toLegacyParallel)
- Update compute logic to handle branch collections
- Add test coverage for new types

Breaking: None (feature flag defaults to false)
Feature: Enables structured branch syntax for future PRs
- Extract kind mapping to helper function for maintainability
- Simplify nested ternary for __parallel assignment using if/else
- Remove type casts by using proper type narrowing
- Add documentation for feature flag dual env var support
- Add JSDoc for toLegacyParallel function behavior
- Improve isDynamicStep boolean logic clarity
- Better handling of nested branch collections in compute/utils
Copilot AI review requested due to automatic review settings October 24, 2025 16:08

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Pull Request Overview

This PR establishes the foundational type system and parser for a unified branch abstraction in dynamic views, enabling support for both parallel and alternate execution paths while maintaining backward compatibility with the existing anonymous parallel syntax.

Key Changes:

  • Added DynamicBranchCollection union type system with support for parallel and alternate branch kinds
  • Extended Langium grammar to parse named branch paths with parallel/par/alternate/alt syntax
  • Introduced feature flag system (dynamicBranchCollections) that defaults to OFF, ensuring no behavioral changes

Reviewed Changes

Copilot reviewed 12 out of 12 changed files in this pull request and generated 3 comments.

Show a summary per file
File Description
packages/core/src/types/view-parsed.dynamic.ts Defines new branch collection types, type guards, and legacy compatibility helpers
packages/core/src/types/tests/dynamic-branch.spec.ts Adds comprehensive test coverage for new type guards and helper functions
packages/core/src/config/featureFlags.ts Implements feature flag system for controlled rollout of branch collections
packages/core/src/index.ts Exports feature flag configuration
packages/language-server/src/like-c4.langium Extends grammar with branch collection and branch path syntax
packages/language-server/src/model/parser/ViewsParser.ts Implements parser logic to convert AST to new branch collection types with legacy fallback
packages/language-server/src/model/tests/model-parser-dynamic-views.spec.ts Adds parser tests for named paths and alternate branches
packages/language-server/src/validation/index.ts Updates validation to recognize new AST node types
packages/language-server/src/formatting/LikeC4Formatter.ts Updates formatter to handle branch collection nodes
packages/language-server/src/tests/views-dynamic.spec.ts Updates test expectations for nested parallel validation
packages/core/src/compute-view/dynamic-view/utils.ts Updates flattenSteps to handle new branch collection structures
packages/core/src/compute-view/dynamic-view/compute.ts Extends compute logic to traverse branch collections while maintaining legacy parallel support

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Comment thread packages/core/src/types/view-parsed.dynamic.ts Outdated
Comment thread packages/language-server/src/model/parser/ViewsParser.ts Outdated
Comment thread packages/language-server/src/model/parser/ViewsParser.ts
Jrakru and others added 2 commits October 24, 2025 12:15
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
Signed-off-by: Jrakru <Jrakru@users.noreply.github.com>
- Use direct property check ('paths' in step) instead of function call for better performance in isDynamicStep
- Extract parseValidSteps() helper to eliminate code duplication in parser
- Update parseDynamicBranchPath to use new helper function
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2 participants