| 1 | /** |
| 2 | * Copyright (c) Meta Platforms, Inc. and affiliates. |
| 3 | * |
| 4 | * This source code is licensed under the MIT license found in the |
| 5 | * LICENSE file in the root directory of this source tree. |
| 6 | */ |
| 7 | |
| 8 | import {CompilerError} from '../CompilerError'; |
| 9 | import { |
| 10 | DependencyPathEntry, |
| 11 | GeneratedSource, |
| 12 | Identifier, |
| 13 | PropertyLiteral, |
| 14 | ReactiveScopeDependency, |
| 15 | SourceLocation, |
| 16 | } from '../HIR'; |
| 17 | import {printIdentifier} from '../HIR/PrintHIR'; |
| 18 | |
| 19 | /** |
| 20 | * Simpler fork of DeriveMinimalDependencies, see PropagateScopeDependenciesHIR |
| 21 | * for detailed explanation. |
| 22 | */ |
| 23 | export class ReactiveScopeDependencyTreeHIR { |
| 24 | /** |
| 25 | * Paths from which we can hoist PropertyLoads. If an `identifier`, |
| 26 | * `identifier.path`, or `identifier?.path` is in this map, it is safe to |
| 27 | * evaluate (non-optional) PropertyLoads from. |
| 28 | */ |
| 29 | #hoistableObjects: Map<Identifier, HoistableNode & {reactive: boolean}> = |
| 30 | new Map(); |
| 31 | #deps: Map<Identifier, DependencyNode & {reactive: boolean}> = new Map(); |
| 32 | |
| 33 | /** |
| 34 | * @param hoistableObjects a set of paths from which we can safely evaluate |
| 35 | * PropertyLoads. Note that we expect these to not contain duplicates (e.g. |
| 36 | * both `a?.b` and `a.b`) only because CollectHoistablePropertyLoads merges |
| 37 | * duplicates when traversing the CFG. |
| 38 | */ |
| 39 | constructor(hoistableObjects: Iterable<ReactiveScopeDependency>) { |
| 40 | for (const {path, identifier, reactive, loc} of hoistableObjects) { |
| 41 | let currNode = ReactiveScopeDependencyTreeHIR.#getOrCreateRoot( |
| 42 | identifier, |
| 43 | reactive, |
| 44 | this.#hoistableObjects, |
| 45 | path.length > 0 && path[0].optional ? 'Optional' : 'NonNull', |
| 46 | loc, |
| 47 | ); |
| 48 | |
| 49 | for (let i = 0; i < path.length; i++) { |
| 50 | const prevAccessType = currNode.properties.get( |
| 51 | path[i].property, |
| 52 | )?.accessType; |
| 53 | const accessType = |
| 54 | i + 1 < path.length && path[i + 1].optional ? 'Optional' : 'NonNull'; |
| 55 | CompilerError.invariant( |
| 56 | prevAccessType == null || prevAccessType === accessType, |
| 57 | { |
| 58 | reason: 'Conflicting access types', |
| 59 | loc: GeneratedSource, |
| 60 | }, |
| 61 | ); |
| 62 | let nextNode = currNode.properties.get(path[i].property); |
| 63 | if (nextNode == null) { |
| 64 | nextNode = { |
| 65 | properties: new Map(), |
| 66 | accessType, |
| 67 | loc: path[i].loc, |
| 68 | }; |
| 69 | currNode.properties.set(path[i].property, nextNode); |
| 70 | } |
| 71 | currNode = nextNode; |
| 72 | } |
| 73 | } |
| 74 | } |
| 75 | |
| 76 | static #getOrCreateRoot<T extends string>( |
| 77 | identifier: Identifier, |
| 78 | reactive: boolean, |
| 79 | roots: Map<Identifier, TreeNode<T> & {reactive: boolean}>, |
| 80 | defaultAccessType: T, |
| 81 | loc: SourceLocation, |
| 82 | ): TreeNode<T> { |
| 83 | // roots can always be accessed unconditionally in JS |
| 84 | let rootNode = roots.get(identifier); |
| 85 | |
| 86 | if (rootNode === undefined) { |
| 87 | rootNode = { |
| 88 | properties: new Map(), |
| 89 | reactive, |
| 90 | accessType: defaultAccessType, |
| 91 | loc, |
| 92 | }; |
| 93 | roots.set(identifier, rootNode); |
| 94 | } else { |
| 95 | CompilerError.invariant(reactive === rootNode.reactive, { |
| 96 | reason: '[DeriveMinimalDependenciesHIR] Conflicting reactive root flag', |
| 97 | description: `Identifier ${printIdentifier(identifier)}`, |
| 98 | loc: GeneratedSource, |
| 99 | }); |
| 100 | } |
| 101 | return rootNode; |
| 102 | } |
| 103 | |
| 104 | /** |
| 105 | * Join a dependency with `#hoistableObjects` to record the hoistable |
| 106 | * dependency. This effectively truncates @param dep to its maximal |
| 107 | * safe-to-evaluate subpath |
| 108 | */ |
| 109 | addDependency(dep: ReactiveScopeDependency): void { |
| 110 | const {identifier, reactive, path, loc} = dep; |
| 111 | let depCursor = ReactiveScopeDependencyTreeHIR.#getOrCreateRoot( |
| 112 | identifier, |
| 113 | reactive, |
| 114 | this.#deps, |
| 115 | PropertyAccessType.UnconditionalAccess, |
| 116 | loc, |
| 117 | ); |
| 118 | /** |
| 119 | * hoistableCursor is null if depCursor is not an object we can hoist |
| 120 | * property reads from otherwise, it represents the same node in the |
| 121 | * hoistable / cfg-informed tree |
| 122 | */ |
| 123 | let hoistableCursor: HoistableNode | undefined = |
| 124 | this.#hoistableObjects.get(identifier); |
| 125 | |
| 126 | // All properties read 'on the way' to a dependency are marked as 'access' |
| 127 | for (const entry of path) { |
| 128 | let nextHoistableCursor: HoistableNode | undefined; |
| 129 | let nextDepCursor: DependencyNode; |
| 130 | if (entry.optional) { |
| 131 | /** |
| 132 | * No need to check the access type since we can match both optional or non-optionals |
| 133 | * in the hoistable |
| 134 | * e.g. a?.b<rest> is hoistable if a.b<rest> is hoistable |
| 135 | */ |
| 136 | if (hoistableCursor != null) { |
| 137 | nextHoistableCursor = hoistableCursor?.properties.get(entry.property); |
| 138 | } |
| 139 | |
| 140 | let accessType; |
| 141 | if ( |
| 142 | hoistableCursor != null && |
| 143 | hoistableCursor.accessType === 'NonNull' |
| 144 | ) { |
| 145 | /** |
| 146 | * For an optional chain dep `a?.b`: if the hoistable tree only |
| 147 | * contains `a`, we can keep either `a?.b` or 'a.b' as a dependency. |
| 148 | * (note that we currently do the latter for perf) |
| 149 | */ |
| 150 | accessType = PropertyAccessType.UnconditionalAccess; |
| 151 | } else { |
| 152 | /** |
| 153 | * Given that it's safe to evaluate `depCursor` and optional load |
| 154 | * never throws, it's also safe to evaluate `depCursor?.entry` |
| 155 | */ |
| 156 | accessType = PropertyAccessType.OptionalAccess; |
| 157 | } |
| 158 | nextDepCursor = makeOrMergeProperty( |
| 159 | depCursor, |
| 160 | entry.property, |
| 161 | accessType, |
| 162 | entry.loc, |
| 163 | ); |
| 164 | } else if ( |
| 165 | hoistableCursor != null && |
| 166 | hoistableCursor.accessType === 'NonNull' |
| 167 | ) { |
| 168 | nextHoistableCursor = hoistableCursor.properties.get(entry.property); |
| 169 | nextDepCursor = makeOrMergeProperty( |
| 170 | depCursor, |
| 171 | entry.property, |
| 172 | PropertyAccessType.UnconditionalAccess, |
| 173 | entry.loc, |
| 174 | ); |
| 175 | } else { |
| 176 | /** |
| 177 | * Break to truncate the dependency on its first non-optional entry that PropertyLoads are not hoistable from |
| 178 | */ |
| 179 | break; |
| 180 | } |
| 181 | depCursor = nextDepCursor; |
| 182 | hoistableCursor = nextHoistableCursor; |
| 183 | } |
| 184 | // mark the final node as a dependency |
| 185 | depCursor.accessType = merge( |
| 186 | depCursor.accessType, |
| 187 | PropertyAccessType.OptionalDependency, |
| 188 | ); |
| 189 | } |
| 190 | |
| 191 | deriveMinimalDependencies(): Set<ReactiveScopeDependency> { |
| 192 | const results = new Set<ReactiveScopeDependency>(); |
| 193 | for (const [rootId, rootNode] of this.#deps.entries()) { |
| 194 | collectMinimalDependenciesInSubtree( |
| 195 | rootNode, |
| 196 | rootNode.reactive, |
| 197 | rootId, |
| 198 | [], |
| 199 | results, |
| 200 | ); |
| 201 | } |
| 202 | |
| 203 | return results; |
| 204 | } |
| 205 | |
| 206 | /* |
| 207 | * Prints dependency tree to string for debugging. |
| 208 | * @param includeAccesses |
| 209 | * @returns string representation of DependencyTree |
| 210 | */ |
| 211 | printDeps(includeAccesses: boolean): string { |
| 212 | let res: Array<Array<string>> = []; |
| 213 | |
| 214 | for (const [rootId, rootNode] of this.#deps.entries()) { |
| 215 | const rootResults = printSubtree(rootNode, includeAccesses).map( |
| 216 | result => `${printIdentifier(rootId)}.${result}`, |
| 217 | ); |
| 218 | res.push(rootResults); |
| 219 | } |
| 220 | return res.flat().join('\n'); |
| 221 | } |
| 222 | |
| 223 | static debug<T extends string>(roots: Map<Identifier, TreeNode<T>>): string { |
| 224 | const buf: Array<string> = [`tree() [`]; |
| 225 | for (const [rootId, rootNode] of roots) { |
| 226 | buf.push(`${printIdentifier(rootId)} (${rootNode.accessType}):`); |
| 227 | this.#debugImpl(buf, rootNode, 1); |
| 228 | } |
| 229 | buf.push(']'); |
| 230 | return buf.length > 2 ? buf.join('\n') : buf.join(''); |
| 231 | } |
| 232 | |
| 233 | static #debugImpl<T extends string>( |
| 234 | buf: Array<string>, |
| 235 | node: TreeNode<T>, |
| 236 | depth: number = 0, |
| 237 | ): void { |
| 238 | for (const [property, childNode] of node.properties) { |
| 239 | buf.push(`${' '.repeat(depth)}.${property} (${childNode.accessType}):`); |
| 240 | this.#debugImpl(buf, childNode, depth + 1); |
| 241 | } |
| 242 | } |
| 243 | } |
| 244 | |
| 245 | /* |
| 246 | * Enum representing the access type of single property on a parent object. |
| 247 | * We distinguish on two independent axes: |
| 248 | * Optional / Unconditional: |
| 249 | * - whether this property is an optional load (within an optional chain) |
| 250 | * Access / Dependency: |
| 251 | * - Access: this property is read on the path of a dependency. We do not |
| 252 | * need to track change variables for accessed properties. Tracking accesses |
| 253 | * helps Forget do more granular dependency tracking. |
| 254 | * - Dependency: this property is read as a dependency and we must track changes |
| 255 | * to it for correctness. |
| 256 | * ```javascript |
| 257 | * // props.a is a dependency here and must be tracked |
| 258 | * deps: {props.a, props.a.b} ---> minimalDeps: {props.a} |
| 259 | * // props.a is just an access here and does not need to be tracked |
| 260 | * deps: {props.a.b} ---> minimalDeps: {props.a.b} |
| 261 | * ``` |
| 262 | */ |
| 263 | enum PropertyAccessType { |
| 264 | OptionalAccess = 'OptionalAccess', |
| 265 | UnconditionalAccess = 'UnconditionalAccess', |
| 266 | OptionalDependency = 'OptionalDependency', |
| 267 | UnconditionalDependency = 'UnconditionalDependency', |
| 268 | } |
| 269 | |
| 270 | function isOptional(access: PropertyAccessType): boolean { |
| 271 | return ( |
| 272 | access === PropertyAccessType.OptionalAccess || |
| 273 | access === PropertyAccessType.OptionalDependency |
| 274 | ); |
| 275 | } |
| 276 | function isDependency(access: PropertyAccessType): boolean { |
| 277 | return ( |
| 278 | access === PropertyAccessType.OptionalDependency || |
| 279 | access === PropertyAccessType.UnconditionalDependency |
| 280 | ); |
| 281 | } |
| 282 | |
| 283 | function merge( |
| 284 | access1: PropertyAccessType, |
| 285 | access2: PropertyAccessType, |
| 286 | ): PropertyAccessType { |
| 287 | const resultIsUnconditional = !(isOptional(access1) && isOptional(access2)); |
| 288 | const resultIsDependency = isDependency(access1) || isDependency(access2); |
| 289 | |
| 290 | /* |
| 291 | * Straightforward merge. |
| 292 | * This can be represented as bitwise OR, but is written out for readability |
| 293 | * |
| 294 | * Observe that `UnconditionalAccess | ConditionalDependency` produces an |
| 295 | * unconditionally accessed conditional dependency. We currently use these |
| 296 | * as we use unconditional dependencies. (i.e. to codegen change variables) |
| 297 | */ |
| 298 | if (resultIsUnconditional) { |
| 299 | if (resultIsDependency) { |
| 300 | return PropertyAccessType.UnconditionalDependency; |
| 301 | } else { |
| 302 | return PropertyAccessType.UnconditionalAccess; |
| 303 | } |
| 304 | } else { |
| 305 | // result is optional |
| 306 | if (resultIsDependency) { |
| 307 | return PropertyAccessType.OptionalDependency; |
| 308 | } else { |
| 309 | return PropertyAccessType.OptionalAccess; |
| 310 | } |
| 311 | } |
| 312 | } |
| 313 | |
| 314 | type TreeNode<T extends string> = { |
| 315 | properties: Map<PropertyLiteral, TreeNode<T>>; |
| 316 | accessType: T; |
| 317 | loc: SourceLocation; |
| 318 | }; |
| 319 | type HoistableNode = TreeNode<'Optional' | 'NonNull'>; |
| 320 | type DependencyNode = TreeNode<PropertyAccessType>; |
| 321 | |
| 322 | /** |
| 323 | * Recursively calculates minimal dependencies in a subtree. |
| 324 | * @param node DependencyNode representing a dependency subtree. |
| 325 | * @returns a minimal list of dependencies in this subtree. |
| 326 | */ |
| 327 | function collectMinimalDependenciesInSubtree( |
| 328 | node: DependencyNode, |
| 329 | reactive: boolean, |
| 330 | rootIdentifier: Identifier, |
| 331 | path: Array<DependencyPathEntry>, |
| 332 | results: Set<ReactiveScopeDependency>, |
| 333 | ): void { |
| 334 | if (isDependency(node.accessType)) { |
| 335 | results.add({identifier: rootIdentifier, reactive, path, loc: node.loc}); |
| 336 | } else { |
| 337 | for (const [childName, childNode] of node.properties) { |
| 338 | collectMinimalDependenciesInSubtree( |
| 339 | childNode, |
| 340 | reactive, |
| 341 | rootIdentifier, |
| 342 | [ |
| 343 | ...path, |
| 344 | { |
| 345 | property: childName, |
| 346 | optional: isOptional(childNode.accessType), |
| 347 | loc: childNode.loc, |
| 348 | }, |
| 349 | ], |
| 350 | results, |
| 351 | ); |
| 352 | } |
| 353 | } |
| 354 | } |
| 355 | |
| 356 | function printSubtree( |
| 357 | node: DependencyNode, |
| 358 | includeAccesses: boolean, |
| 359 | ): Array<string> { |
| 360 | const results: Array<string> = []; |
| 361 | for (const [propertyName, propertyNode] of node.properties) { |
| 362 | if (includeAccesses || isDependency(propertyNode.accessType)) { |
| 363 | results.push(`${propertyName} (${propertyNode.accessType})`); |
| 364 | } |
| 365 | const propertyResults = printSubtree(propertyNode, includeAccesses); |
| 366 | results.push(...propertyResults.map(result => `${propertyName}.${result}`)); |
| 367 | } |
| 368 | return results; |
| 369 | } |
| 370 | |
| 371 | function makeOrMergeProperty( |
| 372 | node: DependencyNode, |
| 373 | property: PropertyLiteral, |
| 374 | accessType: PropertyAccessType, |
| 375 | loc: SourceLocation, |
| 376 | ): DependencyNode { |
| 377 | let child = node.properties.get(property); |
| 378 | if (child == null) { |
| 379 | child = { |
| 380 | properties: new Map(), |
| 381 | accessType, |
| 382 | loc, |
| 383 | }; |
| 384 | node.properties.set(property, child); |
| 385 | } else { |
| 386 | child.accessType = merge(child.accessType, accessType); |
| 387 | } |
| 388 | return child; |
| 389 | } |