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JavaScript

import {
eat,
finishToken,
getTokenFromCode,
IdentifierRole,
JSXRole,
match,
next,
skipSpace,
Token,
} from "../../tokenizer/index";
import {TokenType as tt} from "../../tokenizer/types";
import {input, isTypeScriptEnabled, state} from "../../traverser/base";
import {parseExpression, parseMaybeAssign} from "../../traverser/expression";
import {expect, unexpected} from "../../traverser/util";
import {charCodes} from "../../util/charcodes";
import {IS_IDENTIFIER_CHAR, IS_IDENTIFIER_START} from "../../util/identifier";
import {tsTryParseJSXTypeArgument} from "../typescript";
/**
* Read token with JSX contents.
*
* In addition to detecting jsxTagStart and also regular tokens that might be
* part of an expression, this code detects the start and end of text ranges
* within JSX children. In order to properly count the number of children, we
* distinguish jsxText from jsxEmptyText, which is a text range that simplifies
* to the empty string after JSX whitespace trimming.
*
* It turns out that a JSX text range will simplify to the empty string if and
* only if both of these conditions hold:
* - The range consists entirely of whitespace characters (only counting space,
* tab, \r, and \n).
* - The range has at least one newline.
* This can be proven by analyzing any implementation of whitespace trimming,
* e.g. formatJSXTextLiteral in Sucrase or cleanJSXElementLiteralChild in Babel.
*/
function jsxReadToken() {
let sawNewline = false;
let sawNonWhitespace = false;
while (true) {
if (state.pos >= input.length) {
unexpected("Unterminated JSX contents");
return;
}
const ch = input.charCodeAt(state.pos);
if (ch === charCodes.lessThan || ch === charCodes.leftCurlyBrace) {
if (state.pos === state.start) {
if (ch === charCodes.lessThan) {
state.pos++;
finishToken(tt.jsxTagStart);
return;
}
getTokenFromCode(ch);
return;
}
if (sawNewline && !sawNonWhitespace) {
finishToken(tt.jsxEmptyText);
} else {
finishToken(tt.jsxText);
}
return;
}
// This is part of JSX text.
if (ch === charCodes.lineFeed) {
sawNewline = true;
} else if (ch !== charCodes.space && ch !== charCodes.carriageReturn && ch !== charCodes.tab) {
sawNonWhitespace = true;
}
state.pos++;
}
}
function jsxReadString(quote) {
state.pos++;
for (;;) {
if (state.pos >= input.length) {
unexpected("Unterminated string constant");
return;
}
const ch = input.charCodeAt(state.pos);
if (ch === quote) {
state.pos++;
break;
}
state.pos++;
}
finishToken(tt.string);
}
// Read a JSX identifier (valid tag or attribute name).
//
// Optimized version since JSX identifiers can't contain
// escape characters and so can be read as single slice.
// Also assumes that first character was already checked
// by isIdentifierStart in readToken.
function jsxReadWord() {
let ch;
do {
if (state.pos > input.length) {
unexpected("Unexpectedly reached the end of input.");
return;
}
ch = input.charCodeAt(++state.pos);
} while (IS_IDENTIFIER_CHAR[ch] || ch === charCodes.dash);
finishToken(tt.jsxName);
}
// Parse next token as JSX identifier
function jsxParseIdentifier() {
nextJSXTagToken();
}
// Parse namespaced identifier.
function jsxParseNamespacedName(identifierRole) {
jsxParseIdentifier();
if (!eat(tt.colon)) {
// Plain identifier, so this is an access.
state.tokens[state.tokens.length - 1].identifierRole = identifierRole;
return;
}
// Process the second half of the namespaced name.
jsxParseIdentifier();
}
// Parses element name in any form - namespaced, member
// or single identifier.
function jsxParseElementName() {
const firstTokenIndex = state.tokens.length;
jsxParseNamespacedName(IdentifierRole.Access);
let hadDot = false;
while (match(tt.dot)) {
hadDot = true;
nextJSXTagToken();
jsxParseIdentifier();
}
// For tags like <div> with a lowercase letter and no dots, the name is
// actually *not* an identifier access, since it's referring to a built-in
// tag name. Remove the identifier role in this case so that it's not
// accidentally transformed by the imports transform when preserving JSX.
if (!hadDot) {
const firstToken = state.tokens[firstTokenIndex];
const firstChar = input.charCodeAt(firstToken.start);
if (firstChar >= charCodes.lowercaseA && firstChar <= charCodes.lowercaseZ) {
firstToken.identifierRole = null;
}
}
}
// Parses any type of JSX attribute value.
function jsxParseAttributeValue() {
switch (state.type) {
case tt.braceL:
next();
parseExpression();
nextJSXTagToken();
return;
case tt.jsxTagStart:
jsxParseElement();
nextJSXTagToken();
return;
case tt.string:
nextJSXTagToken();
return;
default:
unexpected("JSX value should be either an expression or a quoted JSX text");
}
}
// Parse JSX spread child, after already processing the {
// Does not parse the closing }
function jsxParseSpreadChild() {
expect(tt.ellipsis);
parseExpression();
}
// Parses JSX opening tag starting after "<".
// Returns true if the tag was self-closing.
// Does not parse the last token.
function jsxParseOpeningElement(initialTokenIndex) {
if (match(tt.jsxTagEnd)) {
// This is an open-fragment.
return false;
}
jsxParseElementName();
if (isTypeScriptEnabled) {
tsTryParseJSXTypeArgument();
}
let hasSeenPropSpread = false;
while (!match(tt.slash) && !match(tt.jsxTagEnd) && !state.error) {
if (eat(tt.braceL)) {
hasSeenPropSpread = true;
expect(tt.ellipsis);
parseMaybeAssign();
// }
nextJSXTagToken();
continue;
}
if (
hasSeenPropSpread &&
state.end - state.start === 3 &&
input.charCodeAt(state.start) === charCodes.lowercaseK &&
input.charCodeAt(state.start + 1) === charCodes.lowercaseE &&
input.charCodeAt(state.start + 2) === charCodes.lowercaseY
) {
state.tokens[initialTokenIndex].jsxRole = JSXRole.KeyAfterPropSpread;
}
jsxParseNamespacedName(IdentifierRole.ObjectKey);
if (match(tt.eq)) {
nextJSXTagToken();
jsxParseAttributeValue();
}
}
const isSelfClosing = match(tt.slash);
if (isSelfClosing) {
// /
nextJSXTagToken();
}
return isSelfClosing;
}
// Parses JSX closing tag starting after "</".
// Does not parse the last token.
function jsxParseClosingElement() {
if (match(tt.jsxTagEnd)) {
// Fragment syntax, so we immediately have a tag end.
return;
}
jsxParseElementName();
}
// Parses entire JSX element, including its opening tag
// (starting after "<"), attributes, contents and closing tag.
// Does not parse the last token.
function jsxParseElementAt() {
const initialTokenIndex = state.tokens.length - 1;
state.tokens[initialTokenIndex].jsxRole = JSXRole.NoChildren;
let numExplicitChildren = 0;
const isSelfClosing = jsxParseOpeningElement(initialTokenIndex);
if (!isSelfClosing) {
nextJSXExprToken();
while (true) {
switch (state.type) {
case tt.jsxTagStart:
nextJSXTagToken();
if (match(tt.slash)) {
nextJSXTagToken();
jsxParseClosingElement();
// Key after prop spread takes precedence over number of children,
// since it means we switch to createElement, which doesn't care
// about number of children.
if (state.tokens[initialTokenIndex].jsxRole !== JSXRole.KeyAfterPropSpread) {
if (numExplicitChildren === 1) {
state.tokens[initialTokenIndex].jsxRole = JSXRole.OneChild;
} else if (numExplicitChildren > 1) {
state.tokens[initialTokenIndex].jsxRole = JSXRole.StaticChildren;
}
}
return;
}
numExplicitChildren++;
jsxParseElementAt();
nextJSXExprToken();
break;
case tt.jsxText:
numExplicitChildren++;
nextJSXExprToken();
break;
case tt.jsxEmptyText:
nextJSXExprToken();
break;
case tt.braceL:
next();
if (match(tt.ellipsis)) {
jsxParseSpreadChild();
nextJSXExprToken();
// Spread children are a mechanism to explicitly mark children as
// static, so count it as 2 children to satisfy the "more than one
// child" condition.
numExplicitChildren += 2;
} else {
// If we see {}, this is an empty pseudo-expression that doesn't
// count as a child.
if (!match(tt.braceR)) {
numExplicitChildren++;
parseExpression();
}
nextJSXExprToken();
}
break;
// istanbul ignore next - should never happen
default:
unexpected();
return;
}
}
}
}
// Parses entire JSX element from current position.
// Does not parse the last token.
export function jsxParseElement() {
nextJSXTagToken();
jsxParseElementAt();
}
// ==================================
// Overrides
// ==================================
export function nextJSXTagToken() {
state.tokens.push(new Token());
skipSpace();
state.start = state.pos;
const code = input.charCodeAt(state.pos);
if (IS_IDENTIFIER_START[code]) {
jsxReadWord();
} else if (code === charCodes.quotationMark || code === charCodes.apostrophe) {
jsxReadString(code);
} else {
// The following tokens are just one character each.
++state.pos;
switch (code) {
case charCodes.greaterThan:
finishToken(tt.jsxTagEnd);
break;
case charCodes.lessThan:
finishToken(tt.jsxTagStart);
break;
case charCodes.slash:
finishToken(tt.slash);
break;
case charCodes.equalsTo:
finishToken(tt.eq);
break;
case charCodes.leftCurlyBrace:
finishToken(tt.braceL);
break;
case charCodes.dot:
finishToken(tt.dot);
break;
case charCodes.colon:
finishToken(tt.colon);
break;
default:
unexpected();
}
}
}
function nextJSXExprToken() {
state.tokens.push(new Token());
state.start = state.pos;
jsxReadToken();
}