Reanalyze: reactive incremental analysis + churn/mermaid tooling

CHANGELOG.md

@@ -20,20 +20,22 @@
 
 - Add support for Set, Map, WeakSet and WeakMap to `@unboxed`. https://github.com/rescript-lang/rescript/pull/8009
 
+- Reanalyze: add reactive incremental analysis (`-reactive`, `-runs`, `-churn`) and Mermaid pipeline dumping (`-mermaid`). https://github.com/rescript-lang/rescript/pull/8092
+
 #### :bug: Bug fix
 
 #### :memo: Documentation
 
 #### :nail_care: Polish
 
+- Rewatch: enable `--create-sourcedirs` by default (now deprecated when explicitly used). https://github.com/rescript-lang/rescript/pull/8092
+
 #### :house: Internal
 
 # 12.0.2
 
 #### :rocket: New Feature
 
-- Reanalyze: add parallel processing for CMT file analysis with new `-parallel` and `-timing` flags, plus benchmark infrastructure for performance testing. https://github.com/rescript-lang/rescript/pull/8089
-
 #### :bug: Bug fix
 
 - Reanalyze: make optional args analysis liveness-aware, preventing false positives when functions are only called from dead code. https://github.com/rescript-lang/rescript/pull/8082

Makefile

@@ -175,10 +175,7 @@ test-analysis: lib ninja
 test-reanalyze: lib ninja
 	make -C tests/analysis_tests/tests-reanalyze/deadcode test
 
-test-reanalyze-parallel: lib ninja
-	make -C tests/analysis_tests/tests-reanalyze/deadcode test-parallel
-
-# Benchmark parallel analysis on larger codebase (COPIES=N for more files)
+# Benchmark reanalyze on larger codebase (COPIES=N for more files)
 benchmark-reanalyze: lib ninja
 	make -C tests/analysis_tests/tests-reanalyze/deadcode-benchmark benchmark COPIES=$(or $(COPIES),50)
 
@@ -254,4 +251,4 @@ dev-container:
 
 .DEFAULT_GOAL := build
 
-.PHONY: yarn-install build ninja rewatch compiler lib artifacts bench test test-analysis test-reanalyze test-reanalyze-parallel benchmark-reanalyze test-tools test-syntax test-syntax-roundtrip test-gentype test-rewatch test-all playground playground-compiler playground-test playground-cmijs playground-release format checkformat clean-ninja clean-rewatch clean-compiler clean-lib clean-gentype clean-tests clean dev-container
+.PHONY: yarn-install build ninja rewatch compiler lib artifacts bench test test-analysis test-reanalyze benchmark-reanalyze test-tools test-syntax test-syntax-roundtrip test-gentype test-rewatch test-all playground playground-compiler playground-test playground-cmijs playground-release format checkformat clean-ninja clean-rewatch clean-compiler clean-lib clean-gentype clean-tests clean dev-container

analysis/dune

@@ -1,4 +1,4 @@
-(dirs bin src reanalyze vendor)
+(dirs bin src reactive reanalyze vendor)
 
 (env
  (dev

analysis/reactive/Makefile

@@ -0,0 +1,15 @@
+.PHONY: build test clean
+
+# Build the reactive library
+build:
+	dune build src/
+
+# Run all tests
+test:
+	dune build test/ReactiveTest.exe
+	dune exec test/ReactiveTest.exe
+
+# Clean build artifacts
+clean:
+	dune clean
+

analysis/reactive/README.md

@@ -0,0 +1,109 @@
+# Reactive Collections Library
+
+A library for incremental computation using reactive collections with delta-based updates.
+
+## Overview
+
+This library provides composable reactive collections that automatically propagate changes through a computation graph. When source data changes, only the affected parts of derived collections are recomputed.
+
+### Key Features
+
+- **Delta-based updates**: Changes propagate as `Set`, `Remove`, or `Batch` deltas
+- **Glitch-free semantics**: Topological scheduling ensures consistent updates
+- **Composable combinators**: `flatMap`, `join`, `union`, `fixpoint`
+- **Incremental fixpoint**: Efficient transitive closure with support for additions and removals
+
+## Usage
+
+```ocaml
+open Reactive
+
+(* Create a source collection *)
+let (files, emit) = source ~name:"files" ()
+
+(* Derive collections with combinators *)
+let decls = flatMap ~name:"decls" files
+  ~f:(fun _path data -> data.declarations)
+  ()
+
+let refs = flatMap ~name:"refs" files
+  ~f:(fun _path data -> data.references)
+  ~merge:PosSet.union
+  ()
+
+(* Join collections *)
+let resolved = join ~name:"resolved" refs decls
+  ~key_of:(fun pos _ref -> pos)
+  ~f:(fun pos ref decl_opt -> ...)
+  ()
+
+(* Compute transitive closure *)
+let reachable = fixpoint ~name:"reachable"
+  ~init:roots
+  ~edges:graph
+  ()
+
+(* Emit changes *)
+emit (Set ("file.res", file_data))
+emit (Batch [set "a.res" data_a; set "b.res" data_b])
+```
+
+## Combinators
+
+| Combinator | Description |
+|------------|-------------|
+| `source` | Create a mutable source collection |
+| `flatMap` | Transform and flatten entries, with optional merge |
+| `join` | Look up keys from left collection in right collection |
+| `union` | Combine two collections, with optional merge for conflicts |
+| `fixpoint` | Compute transitive closure incrementally |
+
+## Building & Testing
+
+```bash
+# Build the library
+make build
+
+# Run all tests
+make test
+
+# Clean build artifacts
+make clean
+```
+
+## Test Structure
+
+Tests are organized by theme:
+
+| File | Description |
+|------|-------------|
+| `FlatMapTest.ml` | FlatMap combinator tests |
+| `JoinTest.ml` | Join combinator tests |
+| `UnionTest.ml` | Union combinator tests |
+| `FixpointBasicTest.ml` | Basic fixpoint graph traversal |
+| `FixpointIncrementalTest.ml` | Incremental fixpoint updates |
+| `BatchTest.ml` | Batch processing tests |
+| `IntegrationTest.ml` | End-to-end file processing |
+| `GlitchFreeTest.ml` | Glitch-free scheduler tests |
+
+## Glitch-Free Semantics
+
+The scheduler ensures that derived collections never see inconsistent intermediate states:
+
+1. **Topological levels**: Each node has a level based on its dependencies
+2. **Accumulate phase**: All deltas at a level are collected before processing
+3. **Propagate phase**: Nodes process accumulated deltas in level order
+
+This prevents issues like:
+- Anti-joins seeing partial data (e.g., refs without matching decls)
+- Multi-level unions causing spurious additions/removals
+
+## Usage in Reanalyze
+
+This library powers the reactive dead code analysis in reanalyze:
+
+- `ReactiveFileCollection`: Manages CMT file processing
+- `ReactiveMerge`: Merges per-file data into global collections
+- `ReactiveLiveness`: Computes live declarations via fixpoint
+- `ReactiveSolver`: Generates dead code issues reactively
+

analysis/reactive/dune

@@ -0,0 +1 @@
+(dirs src test)