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// NOTE: This file must be compatible with old Node.js versions, since it runs
// during testing.
/**
* @typedef {Object} HelperMetadata
* @property {string[]} globals
* @property {{ [name: string]: string[] }} locals
* @property {{ [name: string]: string[] }} dependencies
* @property {string[]} exportBindingAssignments
* @property {string} exportName
*/
/**
* Given a file AST for a given helper, get a bunch of metadata about it so that Babel can quickly render
* the helper is whatever context it is needed in.
*
* @param {typeof import("@babel/core")} babel
*
* @returns {HelperMetadata}
*/
export function getHelperMetadata(babel, code, helperName) {
const globals = new Set();
// Maps imported identifier name -> helper name
const dependenciesBindings = new Map();
let exportName;
const exportBindingAssignments = [];
// helper name -> reference paths
const dependencies = new Map();
// local variable name -> reference paths
const locals = new Map();
const spansToRemove = [];
const validateDefaultExport = decl => {
if (exportName) {
throw new Error(
`Helpers can have only one default export (in ${helperName})`
);
}
if (!decl.isFunctionDeclaration() || !decl.node.id) {
throw new Error(
`Helpers can only export named function declarations (in ${helperName})`
);
}
};
/** @type {import("@babel/traverse").Visitor} */
const dependencyVisitor = {
Program(path) {
for (const child of path.get("body")) {
if (child.isImportDeclaration()) {
if (
child.get("specifiers").length !== 1 ||
!child.get("specifiers.0").isImportDefaultSpecifier()
) {
throw new Error(
`Helpers can only import a default value (in ${helperName})`
);
}
dependenciesBindings.set(
child.node.specifiers[0].local.name,
child.node.source.value
);
dependencies.set(child.node.source.value, []);
spansToRemove.push([child.node.start, child.node.end]);
child.remove();
}
}
for (const child of path.get("body")) {
if (child.isExportDefaultDeclaration()) {
const decl = child.get("declaration");
validateDefaultExport(decl);
exportName = decl.node.id.name;
spansToRemove.push([child.node.start, decl.node.start]);
child.replaceWith(decl.node);
} else if (
child.isExportNamedDeclaration() &&
child.node.specifiers.length === 1 &&
child.get("specifiers.0.exported").isIdentifier({ name: "default" })
) {
const { name } = child.node.specifiers[0].local;
validateDefaultExport(child.scope.getBinding(name).path);
exportName = name;
spansToRemove.push([child.node.start, child.node.end]);
child.remove();
} else if (
process.env.IS_BABEL_OLD_E2E &&
child.isExportNamedDeclaration() &&
child.node.specifiers.length === 0
) {
spansToRemove.push([child.node.start, child.node.end]);
child.remove();
} else if (
child.isExportAllDeclaration() ||
child.isExportNamedDeclaration()
) {
throw new Error(`Helpers can only export default (in ${helperName})`);
}
}
path.scope.crawl();
const bindings = path.scope.getAllBindings();
Object.keys(bindings).forEach(name => {
if (dependencies.has(name)) return;
const binding = bindings[name];
const references = [
...binding.path.getBindingIdentifierPaths(true)[name].map(makePath),
...binding.referencePaths.map(makePath),
];
for (const violation of binding.constantViolations) {
violation.getBindingIdentifierPaths(true)[name].forEach(path => {
references.push(makePath(path));
});
}
locals.set(name, references);
});
},
ReferencedIdentifier(child) {
const name = child.node.name;
const binding = child.scope.getBinding(name);
if (!binding) {
if (dependenciesBindings.has(name)) {
dependencies
.get(dependenciesBindings.get(name))
.push(makePath(child));
} else if (name !== "arguments" || child.scope.path.isProgram()) {
globals.add(name);
}
}
},
AssignmentExpression(child) {
const left = child.get("left");
if (!(exportName in left.getBindingIdentifiers())) return;
if (!left.isIdentifier()) {
throw new Error(
`Only simple assignments to exports are allowed in helpers (in ${helperName})`
);
}
const binding = child.scope.getBinding(exportName);
if (binding && binding.scope.path.isProgram()) {
exportBindingAssignments.push(makePath(child));
}
},
};
babel.transformSync(code, {
configFile: false,
babelrc: false,
plugins: [() => ({ visitor: dependencyVisitor })],
});
if (!exportName) throw new Error("Helpers must have a named default export.");
// Process these in reverse so that mutating the references does not invalidate any later paths in
// the list.
exportBindingAssignments.reverse();
spansToRemove.sort(([start1], [start2]) => start2 - start1);
for (const [start, end] of spansToRemove) {
code = code.slice(0, start) + code.slice(end);
}
return [
code,
{
globals: Array.from(globals),
locals: Object.fromEntries(locals),
dependencies: Object.fromEntries(dependencies),
exportBindingAssignments,
exportName,
},
];
}
function makePath(path) {
const parts = [];
for (; path.parentPath; path = path.parentPath) {
parts.push(path.key);
if (path.inList) parts.push(path.listKey);
}
return parts.reverse().join(".");
}
export function stringifyMetadata(metadata) {
return `\
{
globals: ${JSON.stringify(metadata.globals)},
locals: ${JSON.stringify(metadata.locals)},
exportBindingAssignments: ${JSON.stringify(metadata.exportBindingAssignments)},
exportName: ${JSON.stringify(metadata.exportName)},
dependencies: ${JSON.stringify(metadata.dependencies)},
}
`;
}
|
