Extract relevant part of stack and make source-tracking optional

Signed-off-by: Darshan Sen <raisinten@gmail.com>

README.md

@@ -46,7 +46,7 @@ process.on("beforeExit", () => {
 });
 
 // Enables tracking require() calls.
-trackRequires(true);
+trackRequires(true, { trackSource: true });
 
 // The assert module takes milliseconds to load, so it would be distinctly
 // visible in the performance trace.

docs/api/README.md

@@ -35,6 +35,8 @@ Call `traceEvents.getEvents()` to get the PerformanceEntry objects in the [Trace
 ]
 ```
 
-## `trackRequires(bool)` (only available in [CommonJS](https://nodejs.org/api/modules.html#modules-commonjs-modules))
+## `trackRequires(switch, options)` (only available in [CommonJS](https://nodejs.org/api/modules.html#modules-commonjs-modules))
 
-Call `trackRequires(true)` to enable tracking `require()`s and call `trackRequires(false)` to disable tracking `require()`s.
+- `switch` (**bool**) - Call `trackRequires(true)` to enable tracking `require()`s and call `trackRequires(false)` to disable tracking `require()`s.
+- `options` (**object**)
+  - `trackSource` (**bool**) - Call `trackRequires(true, { trackSource: true })` to enable tracking `require()`s and also capture the source locations. This creates a throw-away error object and parses the `stack` property, so it introduces an overhead.

docs/examples/tracing-requires/README.md

@@ -8,7 +8,7 @@ Before the process exits, the `TraceEvents` object is destroyed and the trace ev
 
 https://github.com/RaisinTen/perftrace/blob/7cb1ce34d19ed8816e15094b3ef4fd03bb157c76/docs/examples/tracing-requires/index.js#L6-L10
 
-The `require()` calls can be tracked by passing `true` to `trackRequires()` like it is being done in:
+The `require()` calls can be tracked by calling `trackRequires()` like it is being done in:
 
 https://github.com/RaisinTen/perftrace/blob/7cb1ce34d19ed8816e15094b3ef4fd03bb157c76/docs/examples/tracing-requires/index.js#L12
 

docs/examples/tracing-requires/index.js

@@ -9,7 +9,7 @@ process.on("beforeExit", () => {
   writeFileSync("events.json", JSON.stringify(events));
 });
 
-trackRequires(true);
+trackRequires(true, { trackSource: true });
 
 // Express Hello world example
 // Refs: https://expressjs.com/en/starter/hello-world.html

index.cjs

@@ -1,15 +1,15 @@
 const { PerformanceObserver, performance } = require('node:perf_hooks');
 
-// Refs: https://stackoverflow.com/a/47105238
-function thisLine() {
-  const e = new Error();
-  const regex = /\((.*):(\d+):(\d+)\)$/;
-  const match = regex.exec(e.stack.split("\n")[4]);
-  return {
-    filepath: match[1],
-    line: Number(match[2]),
-    column: Number(match[3]),
-  };
+function getSource() {
+  const error = new Error();
+  const stack = error.stack.split("\n");
+  // Ignore the first 3 elements of the error stack to get the relevant source:
+  // Error
+  //     at getSource (.../perftrace/index.cjs:...:...)
+  //     at Module.require (.../perftrace/index.cjs:...:...)
+  //     ...
+  const source = stack.slice(3);
+  return source;
 }
 
 class TraceEvents {
@@ -50,10 +50,13 @@ class TraceEvents {
 const Module = require('module');
 const originalRequire = Module.prototype.require;
 
-function trackRequires(shouldTrackRequires) {
+function trackRequires(shouldTrackRequires, options) {
   if (shouldTrackRequires) {
     Module.prototype.require = function () {
-      const source = thisLine();
+      let source = null;
+      if (options?.trackSource) {
+        source = getSource();
+      }
       performance.mark(`require("${arguments[0]}")`);
       const ret = originalRequire.apply(this, arguments);
       performance.measure(

test/node-test.cjs

@@ -73,6 +73,10 @@ describe("track requires", async () => {
     traceEvents = new TraceEvents();
     trackRequires(true);
     require("node:tls");
+    trackRequires(true, { trackSource: true });
+    require("node:os");
+    trackRequires(true, { trackSource: false });
+    require("node:async_hooks");
     trackRequires(false);
     require("node:net");
 
@@ -83,18 +87,30 @@ describe("track requires", async () => {
     const events = traceEvents.getEvents();
     const requireTls = events.find((element) => element.name === `require("node:tls")`);
     ok(requireTls);
+    const requireOs = events.find((element) => element.name === `require("node:os")`);
+    ok(requireOs);
+    const requireAsyncHooks = events.find((element) => element.name === `require("node:async_hooks")`);
+    ok(requireAsyncHooks);
     const requireNet = events.find((element) => element.name === `require("node:net")`);
     ok(!requireNet);
   });
 
   test("source location", () => {
     const events = traceEvents.getEvents();
+
     const requireTls = events.find((element) => element.name === `require("node:tls")`);
     ok(requireTls);
-    ok(requireTls.args);
-    strictEqual(requireTls.args.filepath, __filename);
-    strictEqual(requireTls.args.line, 75);
-    strictEqual(requireTls.args.column, 5);
+    strictEqual(requireTls.args, null);
+
+    const requireOs = events.find((element) => element.name === `require("node:os")`);
+    ok(requireOs);
+    ok(requireOs.args);
+    ok(requireOs.args.length > 5);
+    ok(requireOs.args[1].includes(__filename));
+
+    const requireAsyncHooks = events.find((element) => element.name === `require("node:async_hooks")`);
+    ok(requireAsyncHooks);
+    strictEqual(requireAsyncHooks.args, null);
   });
 
   after(() => {