import type { Token } from "../parser/tokenizer"; import type TokenProcessor from "../TokenProcessor"; import type RootTransformer from "./RootTransformer"; import Transformer from "./Transformer"; export default class TypeScriptTransformer extends Transformer { readonly rootTransformer: RootTransformer; readonly tokens: TokenProcessor; readonly isImportsTransformEnabled: boolean; constructor(rootTransformer: RootTransformer, tokens: TokenProcessor, isImportsTransformEnabled: boolean); process(): boolean; processEnum(isExport?: boolean): void; /** * Transform an enum into equivalent JS. This has complexity in a few places: * - TS allows string enums, numeric enums, and a mix of the two styles within an enum. * - Enum keys are allowed to be referenced in later enum values. * - Enum keys are allowed to be strings. * - When enum values are omitted, they should follow an auto-increment behavior. */ processEnumBody(enumName: string): void; /** * Detect name information about this enum key, which will be used to determine which code to emit * and whether we should declare a variable as part of this declaration. * * Some cases to keep in mind: * - Enum keys can be implicitly referenced later, e.g. `X = 1, Y = X`. In Sucrase, we implement * this by declaring a variable `X` so that later expressions can use it. * - In addition to the usual identifier key syntax, enum keys are allowed to be string literals, * e.g. `"hello world" = 3,`. Template literal syntax is NOT allowed. * - Even if the enum key is defined as a string literal, it may still be referenced by identifier * later, e.g. `"X" = 1, Y = X`. That means that we need to detect whether or not a string * literal is identifier-like and emit a variable if so, even if the declaration did not use an * identifier. * - Reserved keywords like `break` are valid enum keys, but are not valid to be referenced later * and would be a syntax error if we emitted a variable, so we need to skip the variable * declaration in those cases. * * The variableName return value captures these nuances: if non-null, we can and must emit a * variable declaration, and if null, we can't and shouldn't. */ extractEnumKeyInfo(nameToken: Token): { nameStringCode: string; variableName: string | null; }; /** * Handle an enum member where the RHS is just a string literal (not omitted, not a number, and * not a complex expression). This is the typical form for TS string enums, and in this case, we * do *not* create a reverse mapping. * * This is called after deleting the key token, when the token processor is at the equals sign. * * Example 1: * someKey = "some value" * -> * const someKey = "some value"; MyEnum["someKey"] = someKey; * * Example 2: * "some key" = "some value" * -> * MyEnum["some key"] = "some value"; */ processStringLiteralEnumMember(enumName: string, nameStringCode: string, variableName: string | null): void; /** * Handle an enum member initialized with an expression on the right-hand side (other than a * string literal). In these cases, we should transform the expression and emit code that sets up * a reverse mapping. * * The TypeScript implementation of this operation distinguishes between expressions that can be * "constant folded" at compile time (i.e. consist of number literals and simple math operations * on those numbers) and ones that are dynamic. For constant expressions, it emits the resolved * numeric value, and auto-incrementing is only allowed in that case. Evaluating expressions at * compile time would add significant complexity to Sucrase, so Sucrase instead leaves the * expression as-is, and will later emit something like `MyEnum["previousKey"] + 1` to implement * auto-incrementing. * * This is called after deleting the key token, when the token processor is at the equals sign. * * Example 1: * someKey = 1 + 1 * -> * const someKey = 1 + 1; MyEnum[MyEnum["someKey"] = someKey] = "someKey"; * * Example 2: * "some key" = 1 + 1 * -> * MyEnum[MyEnum["some key"] = 1 + 1] = "some key"; */ processExplicitValueEnumMember(enumName: string, nameStringCode: string, variableName: string | null): void; /** * Handle an enum member with no right-hand side expression. In this case, the value is the * previous value plus 1, or 0 if there was no previous value. We should also always emit a * reverse mapping. * * Example 1: * someKey2 * -> * const someKey2 = someKey1 + 1; MyEnum[MyEnum["someKey2"] = someKey2] = "someKey2"; * * Example 2: * "some key 2" * -> * MyEnum[MyEnum["some key 2"] = someKey1 + 1] = "some key 2"; */ processImplicitValueEnumMember(enumName: string, nameStringCode: string, variableName: string | null, previousValueCode: string | null): void; }