Add script for retrieving original source location

This adds a script that can be used for retrieving the original source
location when given a location in the released extension. It will
download the source map from the Actions workflow run of the release and
use the `source-map` library to extract the original location.

extensions/ql-vscode/scripts/source-map.ts

@@ -0,0 +1,124 @@
+/**
+ * This scripts helps finding the original source file and line number for a
+ * given file and line number in the compiled extension. It currently only
+ * works with released extensions.
+ *
+ * Usage: npx ts-node scripts/source-map.ts <version-number> <filename>:<line>:<column>
+ */
+
+import { spawnSync } from "child_process";
+import { basename, resolve } from "path";
+import { pathExists, readJSON } from "fs-extra";
+import { SourceMapConsumer } from "source-map";
+
+if (process.argv.length !== 4) {
+  console.error(
+    "Expected 2 arguments - the version number and the filename:line number",
+  );
+}
+
+const versionNumber = process.argv[2].startsWith("v")
+  ? process.argv[2]
+  : `v${process.argv[2]}`;
+const filenameAndLine = process.argv[3];
+
+async function extractSourceMap() {
+  const sourceMapsDirectory = resolve(
+    __dirname,
+    "..",
+    "artifacts",
+    "source-maps",
+    versionNumber,
+  );
+
+  if (!(await pathExists(sourceMapsDirectory))) {
+    console.log("Downloading source maps...");
+
+    const workflowRuns = runGhJSON<WorkflowRunListItem[]>([
+      "run",
+      "list",
+      "--workflow",
+      "release.yml",
+      "--branch",
+      versionNumber,
+      "--json",
+      "databaseId,number",
+    ]);
+
+    if (workflowRuns.length !== 1) {
+      throw new Error(
+        `Expected exactly one workflow run for ${versionNumber}, got ${workflowRuns.length}`,
+      );
+    }
+
+    const workflowRun = workflowRuns[0];
+
+    runGh([
+      "run",
+      "download",
+      workflowRun.databaseId.toString(),
+      "--name",
+      "vscode-codeql-sourcemaps",
+      "--dir",
+      sourceMapsDirectory,
+    ]);
+  }
+
+  const [filename, line, column] = filenameAndLine.split(":", 3);
+
+  const fileBasename = basename(filename);
+
+  const sourcemapName = `${fileBasename}.map`;
+  const sourcemapPath = resolve(sourceMapsDirectory, sourcemapName);
+
+  if (!(await pathExists(sourcemapPath))) {
+    throw new Error(`No source map found for ${fileBasename}`);
+  }
+
+  const rawSourceMap = await readJSON(sourcemapPath);
+
+  const originalPosition = await SourceMapConsumer.with(
+    rawSourceMap,
+    null,
+    async function (consumer) {
+      return consumer.originalPositionFor({
+        line: parseInt(line),
+        column: parseInt(column),
+      });
+    },
+  );
+
+  if (!originalPosition.source) {
+    throw new Error(`No source found for ${filenameAndLine}`);
+  }
+
+  const originalFilename = resolve(filename, "..", originalPosition.source);
+
+  console.log(
+    `${originalFilename}:${originalPosition.line}:${originalPosition.column}`,
+  );
+}
+
+extractSourceMap().catch((e: unknown) => {
+  console.error(e);
+  process.exit(2);
+});
+
+function runGh(args: readonly string[]): string {
+  const gh = spawnSync("gh", args);
+  if (gh.status !== 0) {
+    throw new Error(
+      `Failed to get the source map for ${versionNumber}: ${gh.stderr}`,
+    );
+  }
+  return gh.stdout.toString("utf-8");
+}
+
+function runGhJSON<T>(args: readonly string[]): T {
+  return JSON.parse(runGh(args));
+}
+
+type WorkflowRunListItem = {
+  databaseId: number;
+  number: number;
+};