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import type { Logger } from '@metamask/logger';
import type { SyntaxNode } from 'tree-sitter';
import { extractNamesFromDeclaration } from './parse/identifiers.ts';
import { ERROR, RETURN } from './symbols.ts';
import type { EvaluatorState, VariableRecord } from './types.ts';
/**
* Creates a wrapper for a function that throws EvaluatorError if the wrapped function throws.
* This is used to wrap $return, $catch, and $capture to differentiate between internal and user errors.
*
* @param func - The function to wrap.
* @returns A hardened function that wraps the original function.
*/
const wrap = <Args extends unknown[]>(
func: (...args: Args) => void,
): ((...args: Args) => void) => {
return harden((...args: Args) => {
try {
func(...args);
} catch (error) {
throw new EvaluatorError(
'REPL evaluation failed',
'',
error instanceof Error ? error : new Error(String(error)),
);
}
});
};
export type Evaluable = {
endowments: {
consts: VariableRecord;
lets: VariableRecord;
$frame: {
$catch: (caught: unknown) => void;
$capture: (...lets: never[]) => void;
$return?: (...values: never[]) => void;
};
};
code: string;
result: EvaluationResult;
commit: () => void;
};
export type EvaluationResult = {
value?: VariableRecord;
[ERROR]?: unknown;
[RETURN]?: unknown;
};
/**
* Wraps an async evaluation in an IIFE to be awaited outside the compartment.
* Assumes a compartment endowed with `{ consts, lets, $catch, $capture }` at
* least.
*
* TODO: Move this functionality to endojs/endo-evaluator
*
* @param args - The arguments to wrap the async evaluation.
* @param args.consts - The consts to destructure.
* @param args.lets - The lets to destructure.
* @param args.code - The code to evaluate.
* @returns Wrapped code ready to evaluate in a compartment endowed with `{ consts, lets, $catch, $capture }`.
*/
const wrapAsyncEvaluation = ({
consts,
lets,
code,
}: {
consts: VariableRecord;
lets: VariableRecord;
code: string;
}): string => {
const constsKeys = Object.keys(consts);
const letsKeys = Object.keys(lets);
const destructureConsts =
constsKeys.length > 0 ? `const { ${constsKeys.join(',')} } = consts;` : '';
const destructureLets =
letsKeys.length > 0 ? `let { ${letsKeys.join(',')} } = lets;` : '';
// The let namespace can be arbitrarily mutated by the statement; the best
// detection is captureion.
const captureLets =
letsKeys.length > 0 ? `$capture(${letsKeys.join(',')});` : '';
// Async IIFE, to be awaited outside the compartment. We are 'vulnerable' to
// return statements, but we only await whatever is returned; we don't read
// the value. We can also prevent top level return via parsing.
return `(async () => {
await null;
const { $capture, $catch, $return } = $frame;
${destructureConsts}
${destructureLets}
try {
${code}
} catch (e) {
$catch(e);
} finally {
${captureLets}
}
})();`;
};
/**
* Make a captor function that captures names from lexical scope into a record.
*
* Building a function factory from source permits captureion of the
* arguments as individual variables while the record to which they are
* assigned is a reference not endowed to the compartment.
*
* The returned function is wrapped with makeSafe to detect internal errors.
*
* @param names - The names to capture.
* @returns A tuple containing the record and a safe-wrapped function that captures the names into the record.
*/
const makeCaptor = (
names: string[],
): [VariableRecord, (...names: string[]) => void] => {
const $value = '$UNIQUE';
if (names.includes($value)) {
throw new Error(`Captor name "${$value}" is reserved`);
}
const value: VariableRecord = {};
const namespace = names.join(',');
// We use eval safely by constructing the function with care and only
// ever evaluating it in a compartment.
// eslint-disable-next-line @typescript-eslint/no-implied-eval, no-new-func
const captor = Function(
$value,
`return (${namespace}) => void Object.assign(${$value}, { ${namespace} });`,
)(value);
return [value, wrap(captor)];
};
export const prepareEvaluation = (
state: EvaluatorState,
statement: SyntaxNode,
options: { logger?: Logger } = {},
): Evaluable => {
switch (statement.type) {
case 'lexical_declaration':
switch (statement.children[0]?.type) {
case 'const':
return prepareImmutableDeclaration(state, statement, options);
case 'let':
return prepareMutableDeclaration(state, statement, options);
case undefined:
default:
throw new Error(
[
`Unknown lexical_declaration.`,
`statement: ${statement.text}`,
`type: ${statement.toString()}`,
].join('\n'),
);
}
case 'function_declaration':
case 'generator_function_declaration':
return prepareMutableDeclaration(state, statement, options);
case 'variable_declaration':
throw new Error(
`Variable declarations are not allowed: "${statement.text}"`,
);
case 'expression_statement':
return prepareExpression(state, statement, options);
case 'import_statement':
throw new SyntaxError(
'Imports are not allowed. All accessible capabilities are already imported.',
);
case 'if_statement':
case 'for_statement':
case 'for_in_statement':
case 'for_of_statement':
case 'for_await_of_statement':
case 'for_await_in_statement':
case 'for_await_statement':
case 'while_statement':
case 'do_while_statement':
case 'switch_statement':
case 'try_statement':
case 'catch_clause':
case 'finally_clause':
// XXX The above case selector is probably long enough to be the default
return prepareStatement(state, statement, options);
default:
throw new Error(
[
`Unknown statement type.`,
`statement: ${statement.text}`,
`type: ${statement.toString()}`,
].join('\n'),
);
}
};
/**
* Prepare a declaration for evaluation.
*
* @param state - The evaluator state.
* @param statement - The declaration to prepare.
* @returns The prepared declaration.
*/
function prepareDeclaration(
state: EvaluatorState,
statement: SyntaxNode,
): Omit<Evaluable, 'commit'> & { captured: VariableRecord } {
const { consts, lets } = state;
const [captured, $capture] = makeCaptor(Object.keys(lets));
const names = extractNamesFromDeclaration(statement);
const [value, $return] = makeCaptor(names);
const result: EvaluationResult = { value };
const $catch = wrap((caught: unknown) => (result[ERROR] = caught));
return {
endowments: { consts, lets, $frame: { $capture, $catch, $return } },
code: wrapAsyncEvaluation({
consts,
lets,
code: `${statement.text};$return(${names.join(',')});`,
}),
result,
captured,
};
}
/**
* Prepare a mutable declaration (let or function declaration) for evaluation.
*
* @param state - The evaluator state.
* @param statement - The declaration to prepare.
* @param options - The options.
* @param options.logger - The logger.
* @returns The prepared declaration.
*/
function prepareMutableDeclaration(
state: EvaluatorState,
statement: SyntaxNode,
options: { logger?: Logger } = {},
): Evaluable {
const { endowments, code, result, captured } = prepareDeclaration(
state,
statement,
);
const commitLogger = options.logger?.subLogger({ tags: ['commit'] });
return {
endowments,
code,
result,
commit: () => {
commitLogger?.info('captured namespace:', captured);
Object.assign(state.lets, captured);
Iif (result[ERROR]) {
commitLogger?.info('result error:', result[ERROR]);
return;
}
commitLogger?.info('let declaration:', result.value);
Object.assign(state.lets, result.value);
},
};
}
/**
* Prepare an immutable declaration (const declaration) for evaluation.
*
* @param state - The evaluator state.
* @param statement - The declaration to prepare.
* @param options - The options.
* @param options.logger - The logger.
* @returns The prepared declaration.
*/
function prepareImmutableDeclaration(
state: EvaluatorState,
statement: SyntaxNode,
options: { logger?: Logger } = {},
): Evaluable {
const { endowments, code, result, captured } = prepareDeclaration(
state,
statement,
);
const commitLogger = options.logger?.subLogger({ tags: ['commit'] });
return {
endowments,
code,
result,
commit: () => {
commitLogger?.info('captured namespace:', captured);
Object.assign(state.lets, captured);
if (result[ERROR]) {
commitLogger?.info('result error:', result[ERROR]);
return;
}
commitLogger?.info('const declaration:', result.value);
Object.assign(state.consts, result.value);
},
};
}
/**
* Strips any trailing semicolons from the code.
*
* @param code - The code to strip the trailing semicolons from.
* @returns The code without the trailing semicolons.
*/
const stripTrailingSemicolons = (code: string): string =>
code.trimEnd().endsWith(';')
? stripTrailingSemicolons(code.trimEnd().slice(0, -1))
: code.trimEnd();
/**
* Prepare an expression for evaluation.
*
* @param state - The evaluator state.
* @param statement - The expression to prepare.
* @param options - The options.
* @param options.logger - The logger.
* @returns The prepared expression.
*/
function prepareExpression(
state: EvaluatorState,
statement: SyntaxNode,
options: { logger?: Logger } = {},
): Evaluable {
const { consts, lets } = state;
const [captured, $capture] = makeCaptor(Object.keys(lets));
const result: EvaluationResult = {};
const $return = wrap((value: unknown) => (result[RETURN] = value));
const $catch = wrap((caught: unknown) => (result[ERROR] = caught));
const commitLogger = options.logger?.subLogger({ tags: ['commit'] });
return {
endowments: { consts, lets, $frame: { $capture, $catch, $return } },
code: wrapAsyncEvaluation({
consts,
lets,
code: `$return(${stripTrailingSemicolons(statement.text)});`,
}),
result,
commit: () => {
commitLogger?.info('captured namespace:', captured);
Object.assign(state.lets, captured);
if (result[ERROR]) {
commitLogger?.info('result error:', result[ERROR]);
return;
}
commitLogger?.info('result return:', result[RETURN]);
if (!(RETURN in result)) {
throw new Error(
'Internal: Result is undefined but no error was thrown',
);
}
},
};
}
/**
* Prepare an arbitrary statement for evaluation.
*
* @param state - The evaluator state.
* @param statement - The statement to prepare.
* @param options - The options.
* @param options.logger - The logger.
* @returns The prepared statement.
*/
function prepareStatement(
state: EvaluatorState,
statement: SyntaxNode,
options: { logger?: Logger } = {},
): Evaluable {
const { consts, lets } = state;
const [captured, $capture] = makeCaptor(Object.keys(lets));
const result: EvaluationResult = {};
const $catch = wrap((caught: unknown) => (result[ERROR] = caught));
const commitLogger = options.logger?.subLogger({ tags: ['commit'] });
return {
endowments: { consts, lets, $frame: { $capture, $catch } },
code: wrapAsyncEvaluation({
consts,
lets,
code: statement.text,
}),
result,
commit: () => {
commitLogger?.info('captured namespace:', captured);
Object.assign(state.lets, captured);
if (result[ERROR]) {
commitLogger?.info('result error:', result[ERROR]);
}
},
};
}
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