93 lines
2 KiB
JavaScript
93 lines
2 KiB
JavaScript
import {TokenType as tt} from "../parser/tokenizer/types";
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/**
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* Determine information about this named import or named export specifier.
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*
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* This syntax is the `a` from statements like these:
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* import {A} from "./foo";
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* export {A};
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* export {A} from "./foo";
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*
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* As it turns out, we can exactly characterize the syntax meaning by simply
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* counting the number of tokens, which can be from 1 to 4:
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* {A}
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* {type A}
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* {A as B}
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* {type A as B}
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*
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* In the type case, we never actually need the names in practice, so don't get
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* them.
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*
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* TODO: There's some redundancy with the type detection here and the isType
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* flag that's already present on tokens in TS mode. This function could
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* potentially be simplified and/or pushed to the call sites to avoid the object
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* allocation.
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*/
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export default function getImportExportSpecifierInfo(
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tokens,
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index = tokens.currentIndex(),
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) {
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let endIndex = index + 1;
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if (isSpecifierEnd(tokens, endIndex)) {
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// import {A}
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const name = tokens.identifierNameAtIndex(index);
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return {
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isType: false,
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leftName: name,
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rightName: name,
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endIndex,
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};
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}
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endIndex++;
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if (isSpecifierEnd(tokens, endIndex)) {
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// import {type A}
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return {
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isType: true,
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leftName: null,
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rightName: null,
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endIndex,
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};
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}
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endIndex++;
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if (isSpecifierEnd(tokens, endIndex)) {
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// import {A as B}
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return {
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isType: false,
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leftName: tokens.identifierNameAtIndex(index),
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rightName: tokens.identifierNameAtIndex(index + 2),
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endIndex,
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};
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}
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endIndex++;
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if (isSpecifierEnd(tokens, endIndex)) {
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// import {type A as B}
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return {
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isType: true,
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leftName: null,
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rightName: null,
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endIndex,
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};
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}
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throw new Error(`Unexpected import/export specifier at ${index}`);
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}
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function isSpecifierEnd(tokens, index) {
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const token = tokens.tokens[index];
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return token.type === tt.braceR || token.type === tt.comma;
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}
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