microsoft/vscode-react-native

// Copyright (c) Microsoft Corporation. All rights reserved.
// Licensed under the MIT license. See LICENSE file in the project root for details.

import * as url from "url";
import * as path from "path";
import { RawSourceMap } from "source-map";
import { SourceMapsCombinator } from "./sourceMapsCombinator";

const IS_REMOTE = /^[A-Za-z]{2,}:\/\//; // Detection remote sources or specific protocols (like "webpack:///")

interface ISourceMap extends RawSourceMap {
    sections?: ISourceMapSection[];
}
interface ISourceMapSection {
    map: ISourceMap | null;
    offset: { column: number; line: number };
}

export interface IStrictUrl extends url.Url {
    pathname: string;
    href: string;
}

export class SourceMapUtil {
    private static SourceMapURLGlobalRegex: RegExp =
        /\/\/(#|@) sourceMappingURL=((?!data:)[^ ]+?)\s*$/gm;
    private static SourceMapURLRegex: RegExp = /\/\/(#|@) sourceMappingURL=((?!data:)[^ ]+?)\s*$/m;
    private static SourceURLRegex: RegExp = /^\/\/[#@] ?sourceURL=(.+)$/m;

    /**
     * Given a script body and URL, this method parses the body and finds the corresponding source map URL.
     * If the source map URL is not found in the body in the expected form, null is returned.
     */
    public getSourceMapURL(scriptUrl: url.Url, scriptBody: string): IStrictUrl | null {
        let result: IStrictUrl | null = null;

        // scriptUrl = "http://localhost:8081/index.ios.bundle?platform=ios&dev=true"
        const sourceMappingRelativeUrl = this.getSourceMapRelativeUrl(scriptBody); // sourceMappingRelativeUrl = "/index.ios.map?platform=ios&dev=true"
        if (sourceMappingRelativeUrl) {
            const sourceMappingUrl = url.parse(sourceMappingRelativeUrl);
            sourceMappingUrl.protocol = scriptUrl.protocol;
            sourceMappingUrl.host = scriptUrl.host;
            // parse() repopulates all the properties of the URL
            result = <IStrictUrl>url.parse(url.format(sourceMappingUrl));
        }

        return result;
    }

    /**
     * Updates the contents of a source map file to be VS Code friendly:
     * - makes source paths unix style and relative to the sources root path
     * - updates the url of the script file
     * - deletes the script content from the source map
     *
     * @parameter sourceMapBody - body of the source map as generated by the RN Packager.
     * @parameter scriptPath - path of the script file asssociated with this source map.
     * @parameter sourcesRootPath - root path of sources
     *
     */
    public updateSourceMapFile(
        sourceMapBody: string,
        scriptPath: string,
        sourcesRootPath: string,
        packagerRemoteRoot?: string,
        packagerLocalRoot?: string,
    ): string {
        try {
            let sourceMap = <ISourceMap>JSON.parse(sourceMapBody);

            if (sourceMap.sections) {
                // Preserve indexed sourcemap offsets even when Metro emits a null section map.
                sourceMap.sections = sourceMap.sections.map(section => ({
                    ...section,
                    map: section.map ?? SourceMapUtil.createEmptySourceMap(),
                }));

                sourceMap = SourceMapUtil.flattenIndexedSourceMap(sourceMap);
            }

            const sourceMapsCombinator = new SourceMapsCombinator();
            sourceMap = sourceMapsCombinator.convert(sourceMap);

            if (sourceMap.sources) {
                sourceMap.sources = sourceMap.sources.map(sourcePath =>
                    IS_REMOTE.test(sourcePath)
                        ? sourcePath
                        : this.updateSourceMapPath(
                              sourcePath,
                              sourcesRootPath,
                              packagerRemoteRoot,
                              packagerLocalRoot,
                          ),
                );
            }

            delete sourceMap.sourcesContent;
            sourceMap.sourceRoot = "";
            sourceMap.file = scriptPath;
            return JSON.stringify(sourceMap);
        } catch (exception) {
            return sourceMapBody;
        }
    }

    public appendSourceMapPaths(scriptBody: string, sourceMappingUrl: string): string {
        scriptBody += `//# sourceMappingURL=${sourceMappingUrl}`;
        return scriptBody;
    }

    /**
     * Updates source map URLs in the script body.
     */
    public updateScriptPaths(scriptBody: string, sourceMappingUrl: IStrictUrl): string {
        const sourceMapMatch = this.searchSourceMapURL(scriptBody);
        if (sourceMapMatch) {
            // Update the body with the new location of the source map on storage.
            return scriptBody.replace(
                sourceMapMatch[0],
                `//# sourceMappingURL=${path.basename(sourceMappingUrl.pathname)}`,
            );
        }
        return scriptBody;
    }

    /**
     * Removes sourceURL from the script body since RN 0.61 because it breaks sourcemaps.
     * Example: //# sourceURL=http://localhost:8081/index.bundle?platform=android&dev=true&minify=false -> ""
     */
    public removeSourceURL(scriptBody: string): string {
        return scriptBody.replace(SourceMapUtil.SourceURLRegex, "");
    }

    /**
     * Parses the body of a script searching for a source map URL.
     * It supports the following source map url styles:
     *
     *  `//# sourceMappingURL=path/to/source/map`
     *
     *  `//@ sourceMappingURL=path/to/source/map`
     *
     * Returns the last match if found, null otherwise.
     */
    public getSourceMapRelativeUrl(body: string): string | null {
        const sourceMapMatch = this.searchSourceMapURL(body);
        // If match is null, the body doesn't contain the source map
        if (sourceMapMatch) {
            // On React Native macOS 0.62 and RN Windows 0.65 sourceMappingUrl looks like:
            // # sourceMappingURL=//localhost:8081/index.map?platform=macos&dev=true&minify=false
            // Add 'http:' protocol to avoid errors in further processing
            const el = sourceMapMatch[2];
            const macOsOrWin =
                (el.includes("platform=macos") || el.includes("platform=window")) &&
                el.startsWith("//") &&
                !el.includes("http:");

            return macOsOrWin ? `http:${el}` : el;
        }
        return null;
    }

    private searchSourceMapURL(str: string): RegExpMatchArray | null {
        const matchesList = str
            .match(SourceMapUtil.SourceMapURLGlobalRegex)
            ?.filter(s => !s.includes("\\n"));
        if (matchesList && matchesList.length) {
            return matchesList[matchesList.length - 1].match(SourceMapUtil.SourceMapURLRegex);
        }

        return null;
    }

    /**
     * Given an absolute source path, this method does two things:
     * 1. It changes the path from absolute to be relative to the sourcesRootPath parameter.
     * 2. It changes the path separators to Unix style.
     */
    private updateSourceMapPath(
        sourcePath: string,
        sourcesRootPath: string,
        packagerRemoteRoot?: string,
        packagerLocalRoot?: string,
    ) {
        if (packagerRemoteRoot && packagerLocalRoot) {
            packagerRemoteRoot = this.makeUnixStylePath(packagerRemoteRoot);
            packagerLocalRoot = this.makeUnixStylePath(packagerLocalRoot);
            sourcePath = sourcePath.replace(packagerRemoteRoot, packagerLocalRoot);
        }
        const relativeSourcePath = path.relative(sourcesRootPath, sourcePath);
        return this.makeUnixStylePath(relativeSourcePath);
    }

    /**
     * Visual Studio Code source mapping requires Unix style path separators.
     * This method replaces all back-slash characters in a given string with forward-slash ones.
     */
    private makeUnixStylePath(p: string): string {
        const pathArgs = p.split(path.sep);
        return path.posix.join.apply(null, pathArgs);
    }

    private static createEmptySourceMap(): ISourceMap {
        return {
            version: 3,
            sources: [],
            names: [],
            mappings: "",
            file: "",
        };
    }

    private static flattenIndexedSourceMap(sourceMap: ISourceMap): ISourceMap {
        // eslint-disable-next-line @typescript-eslint/no-var-requires
        const flattenSourceMap = require("flatten-source-map");
        const meaningfulSections = (sourceMap.sections ?? []).filter(
            section => section.map && (section.map.sources?.length || section.map.mappings),
        );

        if (meaningfulSections.length === 1 && meaningfulSections[0].map) {
            return meaningfulSections[0].map;
        }

        try {
            return flattenSourceMap(sourceMap);
        } catch (error) {
            if (!meaningfulSections.length) {
                throw error;
            }

            const firstOffset = meaningfulSections[0].offset;
            const rebasedSections = meaningfulSections.map(section => ({
                ...section,
                offset: {
                    line: Math.max(0, section.offset.line - firstOffset.line),
                    column:
                        section.offset.line === firstOffset.line
                            ? Math.max(0, section.offset.column - firstOffset.column)
                            : section.offset.column,
                },
            }));

            return flattenSourceMap({
                ...sourceMap,
                sections: rebasedSections,
            });
        }
    }
}