TypeScript/src/compiler/tracing.ts

/* Tracing events for the compiler. */

/*@internal*/
namespace ts { // eslint-disable-line one-namespace-per-file
    // should be used as tracing?.___
    export let tracing: typeof tracingEnabled | undefined;
    // enable the above using startTracing()

    // `tracingEnabled` should never be used directly, only through the above
    namespace tracingEnabled { // eslint-disable-line one-namespace-per-file
        type Mode = "project" | "build" | "server";

        let fs: typeof import("fs");

        let traceCount = 0;
        let traceFd = 0;

        let mode: Mode;

        const typeCatalog: Type[] = []; // NB: id is index + 1

        let legendPath: string | undefined;
        const legend: TraceRecord[] = [];

        // The actual constraint is that JSON.stringify be able to serialize it without throwing.
        interface Args {
            [key: string]: string | number | boolean | null | undefined | Args | readonly (string | number | boolean | null | undefined | Args)[];
        };

        /** Starts tracing for the given project. */
        export function startTracing(tracingMode: Mode, traceDir: string, configFilePath?: string) {
            Debug.assert(!tracing, "Tracing already started");

            if (fs === undefined) {
                try {
                    fs = require("fs");
                }
                catch (e) {
                    throw new Error(`tracing requires having fs\n(original error: ${e.message || e})`);
                }
            }

            mode = tracingMode;
            typeCatalog.length = 0;

            if (legendPath === undefined) {
                legendPath = combinePaths(traceDir, "legend.json");
            }

            // Note that writing will fail later on if it exists and is not a directory
            if (!fs.existsSync(traceDir)) {
                fs.mkdirSync(traceDir, { recursive: true });
            }

            const countPart =
                mode === "build" ? `.${process.pid}-${++traceCount}`
                : mode === "server" ? `.${process.pid}`
                : ``;
            const tracePath = combinePaths(traceDir, `trace${countPart}.json`);
            const typesPath = combinePaths(traceDir, `types${countPart}.json`);

            legend.push({
                configFilePath,
                tracePath,
                typesPath,
            });

            traceFd = fs.openSync(tracePath, "w");
            tracing = tracingEnabled; // only when traceFd is properly set

            // Start with a prefix that contains some metadata that the devtools profiler expects (also avoids a warning on import)
            const meta = { cat: "__metadata", ph: "M", ts: 1000 * timestamp(), pid: 1, tid: 1 };
            fs.writeSync(traceFd,
                "[\n"
                + [{ name: "process_name", args: { name: "tsc" }, ...meta },
                   { name: "thread_name", args: { name: "Main" }, ...meta },
                   { name: "TracingStartedInBrowser", ...meta, cat: "disabled-by-default-devtools.timeline" }]
                    .map(v => JSON.stringify(v)).join(",\n"));
        }

        /** Stops tracing for the in-progress project and dumps the type catalog. */
        export function stopTracing() {
            Debug.assert(tracing, "Tracing is not in progress");
            Debug.assert(!!typeCatalog.length === (mode !== "server")); // Have a type catalog iff not in server mode

            fs.writeSync(traceFd, `\n]\n`);
            fs.closeSync(traceFd);
            tracing = undefined;

            if (typeCatalog.length) {
                dumpTypes(typeCatalog);
            }
            else {
                // We pre-computed this path for convenience, but clear it
                // now that the file won't be created.
                legend[legend.length - 1].typesPath = undefined;
            }
        }

        export function recordType(type: Type): void {
            if (mode !== "server") {
                typeCatalog.push(type);
            }
        }

        export const enum Phase {
            Parse = "parse",
            Program = "program",
            Bind = "bind",
            Check = "check", // Before we get into checking types (e.g. checkSourceFile)
            CheckTypes = "checkTypes",
            Emit = "emit",
            Session = "session",
        }

        export function instant(phase: Phase, name: string, args?: Args) {
            writeEvent("I", phase, name, args, `"s":"g"`);
        }

        const eventStack: { phase: Phase, name: string, args?: Args, time: number, separateBeginAndEnd: boolean }[] = [];

        /**
         * @param separateBeginAndEnd - used for special cases where we need the trace point even if the event
         * never terminates (typically for reducing a scenario too big to trace to one that can be completed).
         * In the future we might implement an exit handler to dump unfinished events which would deprecate
         * these operations.
         */
        export function push(phase: Phase, name: string, args?: Args, separateBeginAndEnd = false) {
            if (separateBeginAndEnd) {
                writeEvent("B", phase, name, args);
            }
            eventStack.push({ phase, name, args, time: 1000 * timestamp(), separateBeginAndEnd });
        }
        export function pop() {
            Debug.assert(eventStack.length > 0);
            writeStackEvent(eventStack.length - 1, 1000 * timestamp());
            eventStack.length--;
        }
        export function popAll() {
            const endTime = 1000 * timestamp();
            for (let i = eventStack.length - 1; i >= 0; i--) {
                writeStackEvent(i, endTime);
            }
            eventStack.length = 0;
        }
        // sample every 10ms
        const sampleInterval = 1000 * 10;
        function writeStackEvent(index: number, endTime: number) {
            const { phase, name, args, time, separateBeginAndEnd } = eventStack[index];
            if (separateBeginAndEnd) {
                writeEvent("E", phase, name, args, /*extras*/ undefined, endTime);
            }
            // test if [time,endTime) straddles a sampling point
            else if (sampleInterval - (time % sampleInterval) <= endTime - time) {
                writeEvent("X", phase, name, args, `"dur":${endTime - time}`, time);
            }
        }

        function writeEvent(eventType: string, phase: Phase, name: string, args: Args | undefined, extras?: string,
                            time: number = 1000 * timestamp()) {

            // In server mode, there's no easy way to dump type information, so we drop events that would require it.
            if (mode === "server" && phase === Phase.CheckTypes) return;

            performance.mark("beginTracing");
            fs.writeSync(traceFd, `,\n{"pid":1,"tid":1,"ph":"${eventType}","cat":"${phase}","ts":${time},"name":"${name}"`);
            if (extras) fs.writeSync(traceFd, `,${extras}`);
            if (args) fs.writeSync(traceFd, `,"args":${JSON.stringify(args)}`);
            fs.writeSync(traceFd, `}`);
            performance.mark("endTracing");
            performance.measure("Tracing", "beginTracing", "endTracing");
        }

        function getLocation(node: Node | undefined) {
            const file = getSourceFileOfNode(node);
            return !file
                ? undefined
                : {
                    path: file.path,
                    start: indexFromOne(getLineAndCharacterOfPosition(file, node!.pos)),
                    end: indexFromOne(getLineAndCharacterOfPosition(file, node!.end)),
                };

            function indexFromOne(lc: LineAndCharacter): LineAndCharacter {
                return {
                    line: lc.line + 1,
                    character: lc.character + 1,
                };
            }
        }

        function dumpTypes(types: readonly Type[]) {
            performance.mark("beginDumpTypes");

            const typesPath = legend[legend.length - 1].typesPath!;
            const typesFd = fs.openSync(typesPath, "w");

            const recursionIdentityMap = new Map<object, number>();

            // Cleverness: no line break here so that the type ID will match the line number
            fs.writeSync(typesFd, "[");

            const numTypes = types.length;
            for (let i = 0; i < numTypes; i++) {
                const type = types[i];
                const objectFlags = (type as any).objectFlags;
                const symbol = type.aliasSymbol ?? type.symbol;

                // It's slow to compute the display text, so skip it unless it's really valuable (or cheap)
                let display: string | undefined;
                if ((objectFlags & ObjectFlags.Anonymous) | (type.flags & TypeFlags.Literal)) {
                    try {
                        display = type.checker?.typeToString(type);
                    }
                    catch {
                        display = undefined;
                    }
                }

                let indexedAccessProperties: object = {};
                if (type.flags & TypeFlags.IndexedAccess) {
                    const indexedAccessType = type as IndexedAccessType;
                    indexedAccessProperties = {
                        indexedAccessObjectType: indexedAccessType.objectType?.id,
                        indexedAccessIndexType: indexedAccessType.indexType?.id,
                    };
                }

                let referenceProperties: object = {};
                if (objectFlags & ObjectFlags.Reference) {
                    const referenceType = type as TypeReference;
                    referenceProperties = {
                        instantiatedType: referenceType.target?.id,
                        typeArguments: referenceType.resolvedTypeArguments?.map(t => t.id),
                        referenceLocation: getLocation(referenceType.node),
                    };
                }

                let conditionalProperties: object = {};
                if (type.flags & TypeFlags.Conditional) {
                    const conditionalType = type as ConditionalType;
                    conditionalProperties = {
                        conditionalCheckType: conditionalType.checkType?.id,
                        conditionalExtendsType: conditionalType.extendsType?.id,
                        conditionalTrueType: conditionalType.resolvedTrueType?.id ?? -1,
                        conditionalFalseType: conditionalType.resolvedFalseType?.id ?? -1,
                    };
                }

                let substitutionProperties: object = {};
                if (type.flags & TypeFlags.Substitution) {
                    const substitutionType = type as SubstitutionType;
                    substitutionProperties = {
                        substitutionBaseType: substitutionType.baseType?.id,
                        substituteType: substitutionType.substitute?.id,
                    };
                }

                let reverseMappedProperties: object = {};
                if (objectFlags & ObjectFlags.ReverseMapped) {
                    const reverseMappedType = type as ReverseMappedType;
                    reverseMappedProperties = {
                        reverseMappedSourceType: reverseMappedType.source?.id,
                        reverseMappedMappedType: reverseMappedType.mappedType?.id,
                        reverseMappedConstraintType: reverseMappedType.constraintType?.id,
                    };
                }

                let evolvingArrayProperties: object = {};
                if (objectFlags & ObjectFlags.EvolvingArray) {
                    const evolvingArrayType = type as EvolvingArrayType;
                    evolvingArrayProperties = {
                        evolvingArrayElementType: evolvingArrayType.elementType.id,
                        evolvingArrayFinalType: evolvingArrayType.finalArrayType?.id,
                    };
                }

                // We can't print out an arbitrary object, so just assign each one a unique number.
                // Don't call it an "id" so people don't treat it as a type id.
                let recursionToken: number | undefined;
                const recursionIdentity = type.checker.getRecursionIdentity(type);
                if (recursionIdentity) {
                    recursionToken = recursionIdentityMap.get(recursionIdentity);
                    if (!recursionToken) {
                        recursionToken = recursionIdentityMap.size;
                        recursionIdentityMap.set(recursionIdentity, recursionToken);
                    }
                }

                const descriptor = {
                    id: type.id,
                    intrinsicName: (type as any).intrinsicName,
                    symbolName: symbol?.escapedName && unescapeLeadingUnderscores(symbol.escapedName),
                    recursionId: recursionToken,
                    isTuple: objectFlags & ObjectFlags.Tuple ? true : undefined,
                    unionTypes: (type.flags & TypeFlags.Union) ? (type as UnionType).types?.map(t => t.id) : undefined,
                    intersectionTypes: (type.flags & TypeFlags.Intersection) ? (type as IntersectionType).types.map(t => t.id) : undefined,
                    aliasTypeArguments: type.aliasTypeArguments?.map(t => t.id),
                    keyofType: (type.flags & TypeFlags.Index) ? (type as IndexType).type?.id : undefined,
                    ...indexedAccessProperties,
                    ...referenceProperties,
                    ...conditionalProperties,
                    ...substitutionProperties,
                    ...reverseMappedProperties,
                    ...evolvingArrayProperties,
                    destructuringPattern: getLocation(type.pattern),
                    firstDeclaration: getLocation(symbol?.declarations?.[0]),
                    flags: Debug.formatTypeFlags(type.flags).split("|"),
                    display,
                };

                fs.writeSync(typesFd, JSON.stringify(descriptor));
                if (i < numTypes - 1) {
                    fs.writeSync(typesFd, ",\n");
                }
            }

            fs.writeSync(typesFd, "]\n");

            fs.closeSync(typesFd);

            performance.mark("endDumpTypes");
            performance.measure("Dump types", "beginDumpTypes", "endDumpTypes");
        }

        export function dumpLegend() {
            if (!legendPath) {
                return;
            }

            fs.writeFileSync(legendPath, JSON.stringify(legend));
        }

        interface TraceRecord {
            configFilePath?: string;
            tracePath: string;
            typesPath?: string;
        }
    }

    // define after tracingEnabled is initialized
    export const startTracing = tracingEnabled.startTracing;
    export const dumpTracingLegend = tracingEnabled.dumpLegend;
}