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This commit **fixes a security vulnerability** in the **playground's compiler configuration parsing** by replacing the insecure `new Function()` evaluation with **JSON5.parse** in `compiler/apps/playground/lib/compilation.ts`. This **refactoring** mitigates potential XSS risks and updates the `ConfigEditor.tsx` to support JSON5 syntax, including comments and trailing commas. The change introduces a dedicated `parseConfigOverrides` function and updates the default configuration format. Although some older playground URLs with custom configurations may be affected, the core functionality remains largely compatible, and the update is validated with **new unit and E2E tests**.

This commit delivers a **bug fix** for the **React Compiler**'s **memoization validation** logic, specifically resolving false positives within `ValidatePreserveExistingMemo`. It **refactors** the `recordDepsInValue` and `visitInstruction` functions in `compiler/packages/babel-plugin-react-compiler/src/Validation/ValidatePreservedManualMemoization.ts` to correctly identify and ignore dependency mismatches that arise when the compiler can memoize more precisely than the original `useMemo`, particularly with destructured values. This prevents the compiler from incorrectly flagging valid `useMemo` patterns where its optimized dependency analysis differs from the original `useMemo` dependencies. The change improves the **compiler's accuracy** and reduces developer friction by allowing more effective memoization without erroneous warnings.

This commit provides a **bug fix** and **workaround** for an issue within the **Babel plugin for React Compiler** where Babel's compact mode produces invalid JavaScript for negative numeric literals. It modifies the codegen logic in `compiler/packages/babel-plugin-react-compiler/src/ReactiveScopes/CodegenReactiveFunction.ts` to **emit unary expressions** (e.g., `-(1)`) instead of direct negative numbers. This ensures that the generated code remains valid and parsable, even when processed by Babel in compact mode. New test fixtures and an update to enable compact mode in `compiler/packages/snap/src/compiler.ts` were added to validate this critical fix.

This commit introduces an **experimental configuration option**, `customOptOutDirectives`, within the **`babel-plugin-react-compiler`** to allow developers to specify their own custom directives for opting out of compiler features. This **new capability** enhances flexibility by enabling the compiler's directive parsing logic to respect user-defined opt-out rules, particularly for memoization. The change involves updating the **compiler's entrypoint options and program processing** to integrate this new setting, alongside **refactoring** of pragma parsing utilities in `TestUtils.ts` and the addition of **new test cases** to validate the functionality.

This commit introduces a **feature enhancement** to the **React Compiler**, enabling it to correctly infer effect dependencies when **optional chaining** (`?.`) is used in component logic. It updates the core **dependency inference logic** within `InferEffectDependencies.ts` and adds new utility functions in `ScopeDependencyUtils.ts` to properly model optional chain expressions within the compiler's High-level Intermediate Representation (HIR). This ensures that expressions involving optional chains are accurately tracked as dependencies, preventing potential issues with incorrect memoization or re-renders. This **correctness improvement** enhances the reliability of the compiler's optimizations for components utilizing modern JavaScript syntax, with new and updated test fixtures validating the behavior. While a temporary solution, it significantly improves the compiler's understanding of reactive scopes.

This commit introduces a **`reactive` flag** to **scope dependencies** within the **React Compiler's High-Level Intermediate Representation (HIR)**. This **refactoring** modifies the core `ReactiveScopeDependency` type and updates various dependency collection and propagation passes, such as `CollectHoistablePropertyLoads` and `DeriveMinimalDependenciesHIR`, to track and propagate this new boolean property. The change provides more granular information about the reactivity of specific dependencies, laying crucial groundwork for future compiler optimizations. Specifically, it prepares the **compiler** for subsequent work that will rewrite scope dependencies into more efficient instructions, enabling more precise invalidation and performance improvements. While currently, some non-reactive properties of reactive objects might be broadly marked as reactive, this enhancement is a significant step towards more accurate dependency tracking.

This commit performs a significant **refactoring** within the **React Compiler's Babel plugin** to **prepare the `HIRBuilder` for use by later compiler passes**. It centralizes contextual information by moving the `parentFunction` property from the `HIRBuilder` directly into the `Environment` object, which the builder now accesses. The `HIRBuilder`'s constructor was updated to use an options object for improved extensibility, and the `lower` function signatures in `BuildHIR.ts` were adjusted to align with these changes. This work enhances the modularity and reusability of the **HIR construction** process, enabling more sophisticated analysis and transformations in subsequent compiler stages.

This commit introduces an **experimental `dynamicGating` feature** to the **`babel-plugin-react-compiler`**, enabling directive-based conditional compilation. This **new capability** allows developers to control the application of compiler optimizations at runtime by using `use memo if(...)` directives, paired with a file-level `@dynamicGating` annotation. The compiler now generates code that can dynamically switch between an optimized and an original component version based on a runtime condition. This **feature** significantly enhances the **gating and memoization subsystems**, providing a mechanism for **phased rollouts and A/B testing** of compiler-optimized components. Extensive **test coverage** has been added to validate its behavior across various scenarios.

This commit **fixes edge cases** in the **React Compiler's Babel plugin** related to `noEmit` configurations and module-level opt-outs. It **refactors the entrypoint program compilation logic** within `compiler/packages/babel-plugin-react-compiler/src/Entrypoint/Program.ts` to correctly respect these settings, ensuring that no unexpected runtime code is emitted when `noEmit` is active and properly handling modules that opt out of compilation. The changes introduce a new `hasModuleScopeOptOut` property in `ProgramContext` for tracking module-level opt-out status and improve error handling for unexpected compiled functions. This work is a **bug fix** that enhances the **compiler's reliability** and correctness for various project configurations.

This commit **refactors** the **React Compiler's program traversal logic** to significantly improve readability and reduce complexity within the **Babel plugin's entrypoint**. It breaks down the lengthy `compileProgram` function into several smaller, more manageable helper functions, and centralizes compilation options, filename, code, and state management within the `ProgramContext`. This **internal restructuring** enhances the **maintainability** of the compiler's core logic by clarifying control flow and state handling, with **no functional changes** to the compilation output.

This commit **standardizes the pragma format** within the **React Compiler's Babel plugin**, introducing a unified parsing logic for test-only, boolean, and JSON-valued configuration pragmas. This **refactoring** enhances consistency and maintainability of compiler configurations by centralizing pragma interpretation in `TestUtils.ts` and delegating parsing from `makePluginOptions`. The change impacts the **compiler's internal configuration handling** and necessitates widespread updates to **test fixtures and e2e snapshots** across the `babel-plugin-react-compiler` and `playground` modules to conform to the new pragma syntax.

This commit performs a **refactoring** within the **Babel plugin React compiler** to enhance modularity and reduce complexity. It **extracts test-specific configuration parsing logic**, including functions like `parseConfigPragmaForTests`, from the central `HIR/Environment.ts` module. This logic is now housed in a **new utility file**, `Utils/TestUtils.ts`, which also introduces related defaults and parsing functions like `parseConfigPragmaEnvironmentForTest`. The change **isolates testing concerns** from core environment configuration, requiring updates to import paths across the `compiler` and `snap` packages to reflect the relocation.

This commit introduces **new test fixtures** to the **React Compiler**'s Babel plugin, specifically designed to **reproduce and validate edge cases** in its behavior. It adds tests for the interaction between the `use memo` directive and the **`noEmit` directive**, ensuring the compiler correctly handles scenarios where output generation should be suppressed. Additionally, a test case verifies the compiler's outlining logic, confirming that outlining correctly **does not occur** in specific bailout situations when `panicThreshold(none)` is configured. These additions enhance the **compiler's robustness** by covering more complex scenarios and preventing regressions related to these critical directives and optimization behaviors.

This commit introduces a **new test fixture** to reproduce a specific **error scenario** within the **`babel-plugin-react-compiler`**. It adds a JavaScript test case, `error.todo-fbt-param-nested-fbt.js`, demonstrating a problematic usage of **nested FBT calls** that currently causes **Babel build failures**. The accompanying `error.todo-fbt-param-nested-fbt.expect.md` documents the expected error output for this case. This **maintenance** work is crucial for improving the **compiler's robustness** by providing a clear reproduction for an issue that ideally should be detected and gracefully handled to prevent build failures.

This commit introduces a **bug fix** to the **React Compiler**, specifically within the `PruneHoistedContexts` phase of `babel-plugin-react-compiler`. It implements a **bailout mechanism** to prevent incorrect compilation when **hoisted function declarations** are referenced before their definition within a **memo block**. This ensures the compiler avoids generating invalid JavaScript, though it currently results in "false positives" by bailing out on some safely rewritable scenarios. The change prioritizes correctness by preventing potential runtime errors caused by improper hoisting rewrites.

This commit introduces a **bug fix** to the **React Compiler's Intermediate Representation (HIR)**, specifically addressing incorrect handling of **hoisted context variables** that led to duplicate declarations. It **expands the `StoreContext` instruction** within the **HIR** to explicitly store the declaration kind (`Const`, `Let`, `Function`, or `Reassign`), providing more precise semantic information. This change allows the `PruneHoistedContexts` pass to correctly identify and eliminate redundant `DeclareContext` instructions, ensuring accurate representation of variable scopes and lifetimes. The **compiler's `BuildHIR` and `PruneHoistedContexts` passes**, along with **inference and codegen modules**, are updated to leverage this enhanced `StoreContext`, improving the correctness of the generated output for hoisted `let` and `const` declarations.

This commit **fixes a bug** in the **React Compiler's effects inference model**, specifically within the `babel-plugin-react-compiler` package. It addresses an edge case where **returned function expressions** were sometimes incorrectly inferred as 'frozen', even when they captured and mutated their outer context. The **bug fix** updates the `InferReferenceEffects.ts` module to ensure that returned values are only typed as 'frozen' if they are local and do not modify their surrounding scope. This **improves the correctness** of the compiler's analysis, preventing potential runtime issues from incorrect immutability assumptions for functions. New test fixtures are added to validate these specific scenarios.

This commit introduces a **new fallback mechanism** within the **React Compiler's effect dependency inference** to handle scenarios where standard inference fails due to memoization bailouts or unexpected mutable ranges, such as writes to refs. This **enhancement improves the robustness and accuracy** of dependency detection by directly traversing the effect lambda, leveraging logic similar to `PropagateScopeDependencies` to collect loads, hoistable accesses, and property paths. The primary implementation is in `InferEffectDependencies.ts`, with supporting changes in `CollectHoistablePropertyLoads.ts` and `PropagateScopeDependenciesHIR.ts` to facilitate this new approach. This **new capability** ensures the compiler can correctly identify minimal dependencies in complex cases, thereby preventing incorrect re-renders or missed updates in applications.

This commit **fixes a bug** in the **React Compiler's** `InferReactivePlaces` pass, which incorrectly identified stable-typed value blocks, such as ternary expressions involving `setState`, as non-reactive. It introduces a `StableSidemap` class and new utility functions in `compiler/packages/babel-plugin-react-compiler/src/HIR/HIR.ts` to accurately track and propagate stability. This **corrects the inference of reactive places** crucial for **inferred effect dependencies** and **inlined JSX**, ensuring these experimental compiler features behave as expected. The fix prevents incorrect optimizations or runtime issues by properly identifying **reactive refs** in complex control flow. New test fixtures are included to validate the corrected behavior for reactive refs within ternary expressions.

This commit implements a **maintenance fix** to resolve **non-deterministic builds** affecting the **`eslint-plugin-react-hooks`** package. The issue stemmed from inconsistent module wrapping by the Rollup commonjs plugin, particularly with cyclic dependencies involving `@babel/helper-string-parser` and `@babel/types`. To ensure build reliability and consistency, the Rollup configuration in `scripts/rollup/build.js` has been updated to explicitly set `strictRequires: true` for the commonjs plugin. This change forces all CommonJS modules to be wrapped, preventing build variations and guaranteeing more predictable CI outcomes, with a minor (~1.8%) increase in the `eslint-plugin-react-hooks` bundle size.