chore: run type tests using old version of TS

scripts/verifyOldTs.js

@@ -70,4 +70,153 @@ function smoketest() {
   }
 }
 
+function typeTests() {
+  const cwd = path.resolve(__dirname, '../');
+  const rootPackageJson = require('../package.json');
+
+  const currentTsdTypescriptVersion =
+    rootPackageJson.devDependencies['@tsd/typescript'];
+  const currentTypescriptVersion =
+    rootPackageJson.devDependencies['typescript'];
+  const apiExtractorTypescriptVersion =
+    require('@microsoft/api-extractor/package.json').dependencies['typescript'];
+
+  try {
+    const {stdout: statusStdout} = execa.sync(
+      'git',
+      ['status', '--porcelain'],
+      {cwd},
+    );
+
+    if (statusStdout.length > 0) {
+      throw new Error(
+        'Repo is not clean - cannot run type tests with old typescript version',
+      );
+    }
+
+    execa.sync(
+      'yarn',
+      [
+        'set',
+        'resolution',
+        `@tsd/typescript@npm:${currentTsdTypescriptVersion}`,
+        tsVersion,
+      ],
+      {cwd},
+    );
+
+    verifyInstalledTsdTypescript();
+
+    execa.sync(
+      'yarn',
+      [
+        'set',
+        'resolution',
+        `typescript@npm:${currentTypescriptVersion}`,
+        tsVersion,
+      ],
+      {cwd},
+    );
+    execa.sync(
+      'yarn',
+      [
+        'set',
+        'resolution',
+        `typescript@npm:${apiExtractorTypescriptVersion}`,
+        tsVersion,
+      ],
+      {cwd},
+    );
+    execa.sync('yarn', ['set', 'resolution', 'typescript@npm:*', tsVersion], {
+      cwd,
+    });
+
+    verifyInstalledTypescript();
+
+    execa.sync('yarn', ['test-types'], {cwd, stdio: 'inherit'});
+  } finally {
+    execa.sync('git', ['checkout', 'yarn.lock'], {cwd});
+  }
+
+  function verifyInstalledTsdTypescript() {
+    const tsdEntries = listInstalledVersion('@tsd/typescript');
+
+    if (tsdEntries.length !== 1) {
+      throw new Error(
+        `More than one version of @tsd/typescript found: ${tsdEntries.join(
+          ', ',
+        )}`,
+      );
+    }
+
+    const tsdVersion = tsdEntries[0].match(/@npm:(\d+\.\d+)\.\d+/);
+
+    if (!tsdVersion) {
+      throw new Error('Unable to verify installed version of @tsd/typescript');
+    }
+
+    if (tsdVersion[1] !== tsVersion) {
+      throw new Error(
+        `Installed TSD version is not ${tsVersion}, is ${tsdVersion[1]}`,
+      );
+    }
+  }
+
+  function verifyInstalledTypescript() {
+    const typescriptEntries = listInstalledVersion('typescript');
+
+    if (typescriptEntries.length !== 1) {
+      throw new Error(
+        `More than one version of typescript found: ${typescriptEntries.join(
+          ', ',
+        )}`,
+      );
+    }
+
+    const tsdVersion = typescriptEntries[0].match(/@npm%3A(\d+\.\d+)\.\d+/);
+
+    if (!tsdVersion) {
+      throw new Error('Unable to verify installed version of typescript');
+    }
+
+    if (tsdVersion[1] !== tsVersion) {
+      throw new Error(
+        `Installed TSD version is not ${tsVersion}, is ${tsdVersion[1]}`,
+      );
+    }
+  }
+
+  function listInstalledVersion(module) {
+    const {stdout: tsdWhyOutput} = execa.sync(
+      'yarn',
+      ['why', module, '--json'],
+      {cwd},
+    );
+
+    const locators = tsdWhyOutput
+      .split('\n')
+      .map(JSON.parse)
+      .map(entry => {
+        const entries = Object.entries(entry.children);
+        if (entries.length !== 1) {
+          throw new Error(
+            `More than one entry found in ${JSON.stringify(entry, null, 2)}`,
+          );
+        }
+
+        return entries[0][1].locator;
+      });
+
+    return Array.from(new Set(locators));
+  }
+}
+
+console.log(chalk.inverse(` Running smoketest using TypeScript@${tsVersion} `));
 smoketest();
+console.log(chalk.inverse.green(' Successfully ran smoketest '));
+
+console.log(
+  chalk.inverse(` Running type tests using TypeScript@${tsVersion} `),
+);
+typeTests();
+console.log(chalk.inverse.green(' Successfully ran type tests '));