forked from graphql/graphql-js
/
printError.js
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/
printError.js
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/**
* Copyright (c) Facebook, Inc. and its affiliates.
*
* This source code is licensed under the MIT license found in the
* LICENSE file in the root directory of this source tree.
*
* @flow strict
*/
import { type SourceLocation, getLocation } from '../language/location';
import { type Source } from '../language/source';
import { type GraphQLError } from './GraphQLError';
/**
* Prints a GraphQLError to a string, representing useful location information
* about the error's position in the source.
*/
export function printError(error: GraphQLError): string {
const printedLocations = [];
if (error.nodes) {
for (const node of error.nodes) {
if (node.loc) {
printedLocations.push(
highlightSourceAtLocation(
node.loc.source,
getLocation(node.loc.source, node.loc.start),
),
);
}
}
} else if (error.source && error.locations) {
const source = error.source;
for (const location of error.locations) {
printedLocations.push(highlightSourceAtLocation(source, location));
}
}
return printedLocations.length === 0
? error.message
: [error.message, ...printedLocations].join('\n\n') + '\n';
}
/**
* Render a helpful description of the location of the error in the GraphQL
* Source document.
*/
function highlightSourceAtLocation(
source: Source,
location: SourceLocation,
): string {
const firstLineColumnOffset = source.locationOffset.column - 1;
const body = whitespace(firstLineColumnOffset) + source.body;
const lineIndex = location.line - 1;
const lineOffset = source.locationOffset.line - 1;
const lineNum = location.line + lineOffset;
const columnOffset = location.line === 1 ? firstLineColumnOffset : 0;
const columnNum = location.column + columnOffset;
const lines = body.split(/\r\n|[\n\r]/g);
return (
`${source.name} (${lineNum}:${columnNum})\n` +
printPrefixedLines([
// Lines specified like this: ["prefix", "string"],
[`${lineNum - 1}: `, lines[lineIndex - 1]],
[`${lineNum}: `, lines[lineIndex]],
['', whitespace(columnNum - 1) + '^'],
[`${lineNum + 1}: `, lines[lineIndex + 1]],
])
);
}
function printPrefixedLines(lines: Array<[string, string]>): string {
const existingLines = lines.filter(([_, line]) => line !== undefined);
let padLen = 0;
for (const [prefix] of existingLines) {
padLen = Math.max(padLen, prefix.length);
}
return existingLines
.map(([prefix, line]) => lpad(padLen, prefix) + line)
.join('\n');
}
function whitespace(len: number): string {
return Array(len + 1).join(' ');
}
function lpad(len: number, str: string): string {
return whitespace(len - str.length) + str;
}