| 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 | * @flow strict-local |
| 8 | */ |
| 9 | |
| 10 | import type { |
| 11 | HookMap, |
| 12 | HookMapEntry, |
| 13 | HookMapLine, |
| 14 | HookMapMappings, |
| 15 | } from './generateHookMap'; |
| 16 | import type {Position} from './astUtils'; |
| 17 | import {NO_HOOK_NAME} from './astUtils'; |
| 18 | |
| 19 | /** |
| 20 | * Finds the Hook name assigned to a given location in the source code, |
| 21 | * and a HookMap extracted from an extended source map. |
| 22 | * The given location must correspond to the location in the *original* |
| 23 | * source code (i.e. *not* the generated one). |
| 24 | * |
| 25 | * Note that all locations in the source code are guaranteed to map |
| 26 | * to a name, including a sentinel value that represents a missing |
| 27 | * Hook name: '<no-hook>'. |
| 28 | * |
| 29 | * For more details on the format of the HookMap, see generateHookMap |
| 30 | * and the tests for that function and this function. |
| 31 | */ |
| 32 | export function getHookNameForLocation( |
| 33 | location: Position, |
| 34 | hookMap: HookMap, |
| 35 | ): string | null { |
| 36 | const {names, mappings} = hookMap; |
| 37 | |
| 38 | // The HookMap mappings are grouped by lines, so first we look up |
| 39 | // which line of mappings covers the target location. |
| 40 | // Note that we expect to find a line since all the locations in the |
| 41 | // source code are guaranteed to map to a name, including a '<no-hook>' |
| 42 | // name. |
| 43 | const foundLine = binSearch(location, mappings, compareLinePositions); |
| 44 | if (foundLine == null) { |
| 45 | throw new Error( |
| 46 | `Expected to find a line in the HookMap that covers the target location at line: ${location.line}, column: ${location.column}`, |
| 47 | ); |
| 48 | } |
| 49 | |
| 50 | let foundEntry; |
| 51 | const foundLineNumber = getLineNumberFromLine(foundLine); |
| 52 | // The line found in the mappings will never be larger than the target |
| 53 | // line, and vice-versa, so if the target line doesn't match the found |
| 54 | // line, we immediately know that it must correspond to the last mapping |
| 55 | // entry for that line. |
| 56 | if (foundLineNumber !== location.line) { |
| 57 | foundEntry = foundLine[foundLine.length - 1]; |
| 58 | } else { |
| 59 | foundEntry = binSearch(location, foundLine, compareColumnPositions); |
| 60 | } |
| 61 | |
| 62 | if (foundEntry == null) { |
| 63 | throw new Error( |
| 64 | `Expected to find a mapping in the HookMap that covers the target location at line: ${location.line}, column: ${location.column}`, |
| 65 | ); |
| 66 | } |
| 67 | |
| 68 | const foundNameIndex = getHookNameIndexFromEntry(foundEntry); |
| 69 | if (foundNameIndex == null) { |
| 70 | throw new Error( |
| 71 | `Expected to find a name index in the HookMap that covers the target location at line: ${location.line}, column: ${location.column}`, |
| 72 | ); |
| 73 | } |
| 74 | const foundName = names[foundNameIndex]; |
| 75 | if (foundName == null) { |
| 76 | throw new Error( |
| 77 | `Expected to find a name in the HookMap that covers the target location at line: ${location.line}, column: ${location.column}`, |
| 78 | ); |
| 79 | } |
| 80 | |
| 81 | if (foundName === NO_HOOK_NAME) { |
| 82 | return null; |
| 83 | } |
| 84 | return foundName; |
| 85 | } |
| 86 | |
| 87 | function binSearch<T>( |
| 88 | location: Position, |
| 89 | items: T[], |
| 90 | compare: ( |
| 91 | location: Position, |
| 92 | items: T[], |
| 93 | index: number, |
| 94 | ) => {index: number | null, direction: number}, |
| 95 | ): T | null { |
| 96 | let count = items.length; |
| 97 | let index = 0; |
| 98 | let firstElementIndex = 0; |
| 99 | let step; |
| 100 | |
| 101 | while (count > 0) { |
| 102 | index = firstElementIndex; |
| 103 | step = Math.floor(count / 2); |
| 104 | index += step; |
| 105 | |
| 106 | const comparison = compare(location, items, index); |
| 107 | if (comparison.direction === 0) { |
| 108 | if (comparison.index == null) { |
| 109 | throw new Error('Expected an index when matching element is found.'); |
| 110 | } |
| 111 | firstElementIndex = comparison.index; |
| 112 | break; |
| 113 | } |
| 114 | |
| 115 | if (comparison.direction > 0) { |
| 116 | index++; |
| 117 | firstElementIndex = index; |
| 118 | count -= step + 1; |
| 119 | } else { |
| 120 | count = step; |
| 121 | } |
| 122 | } |
| 123 | |
| 124 | return firstElementIndex != null ? items[firstElementIndex] : null; |
| 125 | } |
| 126 | |
| 127 | /** |
| 128 | * Compares the target line location to the current location |
| 129 | * given by the provided index. |
| 130 | * |
| 131 | * If the target line location matches the current location, returns |
| 132 | * the index of the matching line in the mappings. In order for a line |
| 133 | * to match, the target line must match the line exactly, or be within |
| 134 | * the line range of the current line entries and the adjacent line |
| 135 | * entries. |
| 136 | * |
| 137 | * If the line doesn't match, returns the search direction for the |
| 138 | * next step in the binary search. |
| 139 | */ |
| 140 | function compareLinePositions( |
| 141 | location: Position, |
| 142 | mappings: HookMapMappings, |
| 143 | index: number, |
| 144 | ): {index: number | null, direction: number} { |
| 145 | const startIndex = index; |
| 146 | const start = mappings[startIndex]; |
| 147 | if (start == null) { |
| 148 | throw new Error(`Unexpected line missing in HookMap at index ${index}.`); |
| 149 | } |
| 150 | const startLine = getLineNumberFromLine(start); |
| 151 | |
| 152 | let endLine; |
| 153 | let endIndex = index + 1; |
| 154 | const end = mappings[endIndex]; |
| 155 | if (end != null) { |
| 156 | endLine = getLineNumberFromLine(end); |
| 157 | } else { |
| 158 | endIndex = startIndex; |
| 159 | endLine = startLine; |
| 160 | } |
| 161 | |
| 162 | // When the line matches exactly, return the matching index |
| 163 | if (startLine === location.line) { |
| 164 | return {index: startIndex, direction: 0}; |
| 165 | } |
| 166 | if (endLine === location.line) { |
| 167 | return {index: endIndex, direction: 0}; |
| 168 | } |
| 169 | |
| 170 | // If we're at the end of the mappings, and the target line is greater |
| 171 | // than the current line, then this final line must cover the |
| 172 | // target location, so we return it. |
| 173 | if (location.line > endLine && end == null) { |
| 174 | return {index: endIndex, direction: 0}; |
| 175 | } |
| 176 | |
| 177 | // If the location is within the current line and the adjacent one, |
| 178 | // we know that the target location must be covered by the current line. |
| 179 | if (startLine < location.line && location.line < endLine) { |
| 180 | return {index: startIndex, direction: 0}; |
| 181 | } |
| 182 | |
| 183 | // Otherwise, return the next direction in the search. |
| 184 | return {index: null, direction: location.line - startLine}; |
| 185 | } |
| 186 | |
| 187 | /** |
| 188 | * Compares the target column location to the current location |
| 189 | * given by the provided index. |
| 190 | * |
| 191 | * If the target column location matches the current location, returns |
| 192 | * the index of the matching entry in the mappings. In order for a column |
| 193 | * to match, the target column must match the column exactly, or be within |
| 194 | * the column range of the current entry and the adjacent entry. |
| 195 | * |
| 196 | * If the column doesn't match, returns the search direction for the |
| 197 | * next step in the binary search. |
| 198 | */ |
| 199 | function compareColumnPositions( |
| 200 | location: Position, |
| 201 | line: HookMapLine, |
| 202 | index: number, |
| 203 | ): {index: number | null, direction: number} { |
| 204 | const startIndex = index; |
| 205 | const start = line[index]; |
| 206 | if (start == null) { |
| 207 | throw new Error( |
| 208 | `Unexpected mapping missing in HookMap line at index ${index}.`, |
| 209 | ); |
| 210 | } |
| 211 | const startColumn = getColumnNumberFromEntry(start); |
| 212 | |
| 213 | let endColumn; |
| 214 | let endIndex = index + 1; |
| 215 | const end = line[endIndex]; |
| 216 | if (end != null) { |
| 217 | endColumn = getColumnNumberFromEntry(end); |
| 218 | } else { |
| 219 | endIndex = startIndex; |
| 220 | endColumn = startColumn; |
| 221 | } |
| 222 | |
| 223 | // When the column matches exactly, return the matching index |
| 224 | if (startColumn === location.column) { |
| 225 | return {index: startIndex, direction: 0}; |
| 226 | } |
| 227 | if (endColumn === location.column) { |
| 228 | return {index: endIndex, direction: 0}; |
| 229 | } |
| 230 | |
| 231 | // If we're at the end of the entries for this line, and the target |
| 232 | // column is greater than the current column, then this final entry |
| 233 | // must cover the target location, so we return it. |
| 234 | if (location.column > endColumn && end == null) { |
| 235 | return {index: endIndex, direction: 0}; |
| 236 | } |
| 237 | |
| 238 | // If the location is within the current column and the adjacent one, |
| 239 | // we know that the target location must be covered by the current entry. |
| 240 | if (startColumn < location.column && location.column < endColumn) { |
| 241 | return {index: startIndex, direction: 0}; |
| 242 | } |
| 243 | |
| 244 | // Otherwise, return the next direction in the search. |
| 245 | return {index: null, direction: location.column - startColumn}; |
| 246 | } |
| 247 | |
| 248 | function getLineNumberFromLine(line: HookMapLine): number { |
| 249 | return getLineNumberFromEntry(line[0]); |
| 250 | } |
| 251 | |
| 252 | function getLineNumberFromEntry(entry: HookMapEntry): number { |
| 253 | const lineNumber = entry[0]; |
| 254 | if (lineNumber == null) { |
| 255 | throw new Error('Unexpected line number missing in entry in HookMap'); |
| 256 | } |
| 257 | return lineNumber; |
| 258 | } |
| 259 | |
| 260 | function getColumnNumberFromEntry(entry: HookMapEntry): number { |
| 261 | const columnNumber = entry[1]; |
| 262 | if (columnNumber == null) { |
| 263 | throw new Error('Unexpected column number missing in entry in HookMap'); |
| 264 | } |
| 265 | return columnNumber; |
| 266 | } |
| 267 | |
| 268 | function getHookNameIndexFromEntry(entry: HookMapEntry): number { |
| 269 | const hookNameIndex = entry[2]; |
| 270 | if (hookNameIndex == null) { |
| 271 | throw new Error('Unexpected hook name index missing in entry in HookMap'); |
| 272 | } |
| 273 | return hookNameIndex; |
| 274 | } |