packages/babel-generator/src/printer.js
import isInteger from "lodash/isInteger";
import repeat from "lodash/repeat";
import Buffer from "./buffer";
import * as n from "./node";
import * as t from "@babel/types";
import * as generatorFunctions from "./generators";
const SCIENTIFIC_NOTATION = /e/i;
const ZERO_DECIMAL_INTEGER = /\.0+$/;
const NON_DECIMAL_LITERAL = /^0[box]/;
const PURE_ANNOTATION_RE = /^\s*[@#]__PURE__\s*$/;
export type Format = {
shouldPrintComment: (comment: string) => boolean,
retainLines: boolean,
retainFunctionParens: boolean,
comments: boolean,
auxiliaryCommentBefore: string,
auxiliaryCommentAfter: string,
compact: boolean | "auto",
minified: boolean,
concise: boolean,
indent: {
adjustMultilineComment: boolean,
style: string,
base: number,
},
decoratorsBeforeExport: boolean,
};
export default class Printer {
constructor(format, map) {
this.format = format || {};
this._buf = new Buffer(map);
}
format: Format;
inForStatementInitCounter: number = 0;
_buf: Buffer;
_printStack: Array<Node> = [];
_indent: number = 0;
_insideAux: boolean = false;
_printedCommentStarts: Object = {};
_parenPushNewlineState: ?Object = null;
_noLineTerminator: boolean = false;
_printAuxAfterOnNextUserNode: boolean = false;
_printedComments: WeakSet = new WeakSet();
_endsWithInteger = false;
_endsWithWord = false;
generate(ast) {
this.print(ast);
this._maybeAddAuxComment();
return this._buf.get();
}
/**
* Increment indent size.
*/
indent(): void {
if (this.format.compact || this.format.concise) return;
this._indent++;
}
/**
* Decrement indent size.
*/
dedent(): void {
if (this.format.compact || this.format.concise) return;
this._indent--;
}
/**
* Add a semicolon to the buffer.
*/
semicolon(force: boolean = false): void {
this._maybeAddAuxComment();
this._append(";", !force /* queue */);
}
/**
* Add a right brace to the buffer.
*/
rightBrace(): void {
if (this.format.minified) {
this._buf.removeLastSemicolon();
}
this.token("}");
}
/**
* Add a space to the buffer unless it is compact.
*/
space(force: boolean = false): void {
if (this.format.compact) return;
if (
(this._buf.hasContent() && !this.endsWith(" ") && !this.endsWith("\n")) ||
force
) {
this._space();
}
}
/**
* Writes a token that can't be safely parsed without taking whitespace into account.
*/
word(str: string): void {
// prevent concatenating words and creating // comment out of division and regex
if (this._endsWithWord || (this.endsWith("/") && str.indexOf("/") === 0)) {
this._space();
}
this._maybeAddAuxComment();
this._append(str);
this._endsWithWord = true;
}
/**
* Writes a number token so that we can validate if it is an integer.
*/
number(str: string): void {
this.word(str);
// Integer tokens need special handling because they cannot have '.'s inserted
// immediately after them.
this._endsWithInteger =
isInteger(+str) &&
!NON_DECIMAL_LITERAL.test(str) &&
!SCIENTIFIC_NOTATION.test(str) &&
!ZERO_DECIMAL_INTEGER.test(str) &&
str[str.length - 1] !== ".";
}
/**
* Writes a simple token.
*/
token(str: string): void {
// space is mandatory to avoid outputting <!--
// http://javascript.spec.whatwg.org/#comment-syntax
if (
(str === "--" && this.endsWith("!")) ||
// Need spaces for operators of the same kind to avoid: `a+++b`
(str[0] === "+" && this.endsWith("+")) ||
(str[0] === "-" && this.endsWith("-")) ||
// Needs spaces to avoid changing '34' to '34.', which would still be a valid number.
(str[0] === "." && this._endsWithInteger)
) {
this._space();
}
this._maybeAddAuxComment();
this._append(str);
}
/**
* Add a newline (or many newlines), maintaining formatting.
*/
newline(i?: number): void {
if (this.format.retainLines || this.format.compact) return;
if (this.format.concise) {
this.space();
return;
}
// never allow more than two lines
if (this.endsWith("\n\n")) return;
if (typeof i !== "number") i = 1;
i = Math.min(2, i);
if (this.endsWith("{\n") || this.endsWith(":\n")) i--;
if (i <= 0) return;
for (let j = 0; j < i; j++) {
this._newline();
}
}
endsWith(str: string): boolean {
return this._buf.endsWith(str);
}
removeTrailingNewline(): void {
this._buf.removeTrailingNewline();
}
exactSource(loc: Object, cb: () => void) {
this._catchUp("start", loc);
this._buf.exactSource(loc, cb);
}
source(prop: string, loc: Object): void {
this._catchUp(prop, loc);
this._buf.source(prop, loc);
}
withSource(prop: string, loc: Object, cb: () => void): void {
this._catchUp(prop, loc);
this._buf.withSource(prop, loc, cb);
}
_space(): void {
this._append(" ", true /* queue */);
}
_newline(): void {
this._append("\n", true /* queue */);
}
_append(str: string, queue: boolean = false) {
this._maybeAddParen(str);
this._maybeIndent(str);
if (queue) this._buf.queue(str);
else this._buf.append(str);
this._endsWithWord = false;
this._endsWithInteger = false;
}
_maybeIndent(str: string): void {
// we've got a newline before us so prepend on the indentation
if (this._indent && this.endsWith("\n") && str[0] !== "\n") {
this._buf.queue(this._getIndent());
}
}
_maybeAddParen(str: string): void {
// see startTerminatorless() instance method
const parenPushNewlineState = this._parenPushNewlineState;
if (!parenPushNewlineState) return;
// This function does two things:
// - If needed, prints a parenthesis
// - If the currently printed string removes the need for the paren,
// it resets the _parenPushNewlineState field.
// Almost everything removes the need for a paren, except for
// comments and whitespaces.
let i;
for (i = 0; i < str.length && str[i] === " "; i++) continue;
if (i === str.length) {
// Whitespaces only, the parentheses might still be needed.
return;
}
// Check for newline or comment.
const cha = str[i];
if (cha !== "\n") {
if (
// This is not a comment (it doesn't start with /)
cha !== "/" ||
// This is not a comment (it's a / operator)
i + 1 === str.length
) {
// After a normal token, the parentheses aren't needed anymore
this._parenPushNewlineState = null;
return;
}
const chaPost = str[i + 1];
if (chaPost === "*") {
// This is a block comment
if (PURE_ANNOTATION_RE.test(str.slice(i + 2, str.length - 2))) {
// We avoid printing newlines after #__PURE__ comments (we treat
// then as unary operators), but we must keep the old
// parenPushNewlineState because, if a newline was forbidden, it is
// still forbidden after the comment.
return;
}
// NOTE: code flow continues from here to after these if/elses
} else if (chaPost !== "/") {
// This is neither a block comment, nor a line comment.
// After a normal token, the parentheses aren't needed anymore
this._parenPushNewlineState = null;
return;
}
}
this.token("(");
this.indent();
parenPushNewlineState.printed = true;
}
_catchUp(prop: string, loc: Object) {
if (!this.format.retainLines) return;
// catch up to this nodes newline if we're behind
const pos = loc ? loc[prop] : null;
if (pos?.line != null) {
const count = pos.line - this._buf.getCurrentLine();
for (let i = 0; i < count; i++) {
this._newline();
}
}
}
/**
* Get the current indent.
*/
_getIndent(): string {
return repeat(this.format.indent.style, this._indent);
}
/**
* Set some state that will be modified if a newline has been inserted before any
* non-space characters.
*
* This is to prevent breaking semantics for terminatorless separator nodes. eg:
*
* return foo;
*
* returns `foo`. But if we do:
*
* return
* foo;
*
* `undefined` will be returned and not `foo` due to the terminator.
*/
startTerminatorless(isLabel: boolean = false): Object {
if (isLabel) {
this._noLineTerminator = true;
return null;
} else {
return (this._parenPushNewlineState = {
printed: false,
});
}
}
/**
* Print an ending parentheses if a starting one has been printed.
*/
endTerminatorless(state: Object) {
this._noLineTerminator = false;
if (state?.printed) {
this.dedent();
this.newline();
this.token(")");
}
}
print(node, parent) {
if (!node) return;
const oldConcise = this.format.concise;
if (node._compact) {
this.format.concise = true;
}
const printMethod = this[node.type];
if (!printMethod) {
throw new ReferenceError(
`unknown node of type ${JSON.stringify(
node.type,
)} with constructor ${JSON.stringify(node?.constructor.name)}`,
);
}
this._printStack.push(node);
const oldInAux = this._insideAux;
this._insideAux = !node.loc;
this._maybeAddAuxComment(this._insideAux && !oldInAux);
let needsParens = n.needsParens(node, parent, this._printStack);
if (
this.format.retainFunctionParens &&
node.type === "FunctionExpression" &&
node.extra &&
node.extra.parenthesized
) {
needsParens = true;
}
if (needsParens) this.token("(");
this._printLeadingComments(node);
const loc = t.isProgram(node) || t.isFile(node) ? null : node.loc;
this.withSource("start", loc, () => {
printMethod.call(this, node, parent);
});
this._printTrailingComments(node);
if (needsParens) this.token(")");
// end
this._printStack.pop();
this.format.concise = oldConcise;
this._insideAux = oldInAux;
}
_maybeAddAuxComment(enteredPositionlessNode) {
if (enteredPositionlessNode) this._printAuxBeforeComment();
if (!this._insideAux) this._printAuxAfterComment();
}
_printAuxBeforeComment() {
if (this._printAuxAfterOnNextUserNode) return;
this._printAuxAfterOnNextUserNode = true;
const comment = this.format.auxiliaryCommentBefore;
if (comment) {
this._printComment({
type: "CommentBlock",
value: comment,
});
}
}
_printAuxAfterComment() {
if (!this._printAuxAfterOnNextUserNode) return;
this._printAuxAfterOnNextUserNode = false;
const comment = this.format.auxiliaryCommentAfter;
if (comment) {
this._printComment({
type: "CommentBlock",
value: comment,
});
}
}
getPossibleRaw(node) {
const extra = node.extra;
if (
extra &&
extra.raw != null &&
extra.rawValue != null &&
node.value === extra.rawValue
) {
return extra.raw;
}
}
printJoin(nodes: ?Array, parent: Object, opts = {}) {
if (!nodes?.length) return;
if (opts.indent) this.indent();
const newlineOpts = {
addNewlines: opts.addNewlines,
};
for (let i = 0; i < nodes.length; i++) {
const node = nodes[i];
if (!node) continue;
if (opts.statement) this._printNewline(true, node, parent, newlineOpts);
this.print(node, parent);
if (opts.iterator) {
opts.iterator(node, i);
}
if (opts.separator && i < nodes.length - 1) {
opts.separator.call(this);
}
if (opts.statement) this._printNewline(false, node, parent, newlineOpts);
}
if (opts.indent) this.dedent();
}
printAndIndentOnComments(node, parent) {
const indent = node.leadingComments && node.leadingComments.length > 0;
if (indent) this.indent();
this.print(node, parent);
if (indent) this.dedent();
}
printBlock(parent) {
const node = parent.body;
if (!t.isEmptyStatement(node)) {
this.space();
}
this.print(node, parent);
}
_printTrailingComments(node) {
this._printComments(this._getComments(false, node));
}
_printLeadingComments(node) {
this._printComments(
this._getComments(true, node),
// Don't add leading/trailing new lines to #__PURE__ annotations
true,
);
}
printInnerComments(node, indent = true) {
if (!node.innerComments?.length) return;
if (indent) this.indent();
this._printComments(node.innerComments);
if (indent) this.dedent();
}
printSequence(nodes, parent, opts = {}) {
opts.statement = true;
return this.printJoin(nodes, parent, opts);
}
printList(items, parent, opts = {}) {
if (opts.separator == null) {
opts.separator = commaSeparator;
}
return this.printJoin(items, parent, opts);
}
_printNewline(leading, node, parent, opts) {
// Fast path since 'this.newline' does nothing when not tracking lines.
if (this.format.retainLines || this.format.compact) return;
// Fast path for concise since 'this.newline' just inserts a space when
// concise formatting is in use.
if (this.format.concise) {
this.space();
return;
}
let lines = 0;
// don't add newlines at the beginning of the file
if (this._buf.hasContent()) {
if (!leading) lines++; // always include at least a single line after
if (opts.addNewlines) lines += opts.addNewlines(leading, node) || 0;
const needs = leading ? n.needsWhitespaceBefore : n.needsWhitespaceAfter;
if (needs(node, parent)) lines++;
}
this.newline(lines);
}
_getComments(leading, node) {
// Note, we use a boolean flag here instead of passing in the attribute name as it is faster
// because this is called extremely frequently.
return (
(node && (leading ? node.leadingComments : node.trailingComments)) || []
);
}
_printComment(comment, skipNewLines?: boolean) {
if (!this.format.shouldPrintComment(comment.value)) return;
// Some plugins use this to mark comments as removed using the AST-root 'comments' property,
// where they can't manually mutate the AST node comment lists.
if (comment.ignore) return;
if (this._printedComments.has(comment)) return;
this._printedComments.add(comment);
if (comment.start != null) {
if (this._printedCommentStarts[comment.start]) return;
this._printedCommentStarts[comment.start] = true;
}
const isBlockComment = comment.type === "CommentBlock";
// Add a newline before and after a block comment, unless explicitly
// disallowed
const printNewLines =
isBlockComment && !skipNewLines && !this._noLineTerminator;
if (printNewLines && this._buf.hasContent()) this.newline(1);
if (!this.endsWith("[") && !this.endsWith("{")) this.space();
let val =
!isBlockComment && !this._noLineTerminator
? `//${comment.value}\n`
: `/*${comment.value}*/`;
if (isBlockComment && this.format.indent.adjustMultilineComment) {
const offset = comment.loc?.start.column;
if (offset) {
const newlineRegex = new RegExp("\\n\\s{1," + offset + "}", "g");
val = val.replace(newlineRegex, "\n");
}
const indentSize = Math.max(
this._getIndent().length,
this._buf.getCurrentColumn(),
);
val = val.replace(/\n(?!$)/g, `\n${repeat(" ", indentSize)}`);
}
// Avoid creating //* comments
if (this.endsWith("/")) this._space();
this.withSource("start", comment.loc, () => {
this._append(val);
});
if (printNewLines) this.newline(1);
}
_printComments(comments?: Array<Object>, inlinePureAnnotation?: boolean) {
if (!comments?.length) return;
if (
inlinePureAnnotation &&
comments.length === 1 &&
PURE_ANNOTATION_RE.test(comments[0].value)
) {
this._printComment(
comments[0],
// Keep newlines if the comment marks a standalone call
this._buf.hasContent() && !this.endsWith("\n"),
);
} else {
for (const comment of comments) {
this._printComment(comment);
}
}
}
}
// Expose the node type functions and helpers on the prototype for easy usage.
Object.assign(Printer.prototype, generatorFunctions);
function commaSeparator() {
this.token(",");
this.space();
}