fix: Jest mutli-project-runner still cannot handle exactly one project

Add failing test case

Explicitly distinguish if project has been added using process.cwd

Fix CI errors

Add back old test

e2e/__tests__/multiProjectRunner.test.ts

@@ -199,7 +199,57 @@ test.each([{projectPath: 'packages/somepackage'}, {projectPath: 'packages/*'}])(
     });
 
     const {stdout, stderr, exitCode} = runJest(DIR, ['--no-watchman']);
-    expect(stderr).toContain('PASS packages/somepackage/test.js');
+    expect(stderr).toContain('PASS somepackage packages/somepackage/test.js');
+    expect(stderr).toContain('Test Suites: 1 passed, 1 total');
+    expect(stdout).toEqual('');
+    expect(exitCode).toEqual(0);
+  },
+);
+
+test.each([
+  {displayName: 'p1', projectPath: 'packages/p1'},
+  {displayName: 'p2', projectPath: 'packages/p2'},
+])(
+  'correctly runs a single non-root project',
+  ({projectPath, displayName}: {projectPath: string; displayName: string}) => {
+    writeFiles(DIR, {
+      'package.json': `
+        {
+          "jest": {
+            "projects": [
+              "${projectPath}"
+            ]
+          }
+        }
+      `,
+      'packages/p1/package.json': `
+        {
+          "jest": {
+            "displayName": "p1"
+          }
+        }
+      `,
+      'packages/p1/test.js': `
+        test('1+1', () => {
+          expect(1).toBe(1);
+        });
+      `,
+      'packages/p2/package.json': `
+        {
+          "jest": {
+            "displayName": "p2"
+          }
+        }
+      `,
+      'packages/p2/test.js': `
+        test('1+1', () => {
+          expect(1).toBe(1);
+        });
+      `,
+    });
+
+    const {stdout, stderr, exitCode} = runJest(DIR, ['--no-watchman']);
+    expect(stderr).toContain(`PASS ${displayName} ${projectPath}/test.js`);
     expect(stderr).toContain('Test Suites: 1 passed, 1 total');
     expect(stdout).toEqual('');
     expect(exitCode).toEqual(0);

packages/jest-cli/src/cli/index.ts

@@ -28,9 +28,16 @@ export async function run(maybeArgv?: Array<string>, project?: Config.Path) {
       return;
     }
 
-    const projects = getProjectListFromCLIArgs(argv, project);
-
-    const {results, globalConfig} = await runCLI(argv, projects);
+    const {isGlobalProject, projects} = getProjectListFromCLIArgs(
+      argv,
+      project,
+    );
+
+    const {results, globalConfig} = await runCLI(
+      argv,
+      projects,
+      isGlobalProject,
+    );
     readResultsAndExit(results, globalConfig);
   } catch (error) {
     clearLine(process.stderr);
@@ -83,6 +90,7 @@ const getProjectListFromCLIArgs = (
   argv: Config.Argv,
   project?: Config.Path,
 ) => {
+  let isGlobalProject = false;
   const projects = argv.projects ? argv.projects : [];
 
   if (project) {
@@ -92,17 +100,19 @@ const getProjectListFromCLIArgs = (
   if (!projects.length && process.platform === 'win32') {
     try {
       projects.push(realpath(process.cwd()));
+      isGlobalProject = true;
     } catch (err) {
       // do nothing, just catch error
       // process.binding('fs').realpath can throw, e.g. on mapped drives
     }
   }
 
   if (!projects.length) {
+    isGlobalProject = true;
     projects.push(process.cwd());
   }
 
-  return projects;
+  return {isGlobalProject, projects};
 };
 
 const readResultsAndExit = (

packages/jest-config/src/index.ts

@@ -263,6 +263,7 @@ This usually means that your ${chalk.bold(
 export function readConfigs(
   argv: Config.Argv,
   projectPaths: Array<Config.Path>,
+  isGlobalProject: boolean,
 ): {
   globalConfig: Config.GlobalConfig;
   configs: Array<Config.ProjectConfig>;
@@ -278,26 +279,19 @@ export function readConfigs(
     const parsedConfig = readConfig(argv, projects[0]);
     configPath = parsedConfig.configPath;
 
-    if (parsedConfig.globalConfig.projects) {
-      // If this was a single project, and its config has `projects`
-      // settings, use that value instead.
-      projects = parsedConfig.globalConfig.projects;
-    }
-
     hasDeprecationWarnings = parsedConfig.hasDeprecationWarnings;
     globalConfig = parsedConfig.globalConfig;
     configs = [parsedConfig.projectConfig];
     if (globalConfig.projects && globalConfig.projects.length) {
       // Even though we had one project in CLI args, there might be more
       // projects defined in the config.
+      // In other words, if this was a single project,
+      // and its config has `projects` settings, use that value instead.
       projects = globalConfig.projects;
     }
   }
 
-  if (
-    projects.length > 1 ||
-    (projects.length && typeof projects[0] === 'object')
-  ) {
+  if (projects.length > 0) {
     const parsedConfigs = projects
       .filter(root => {
         // Ignore globbed files that cannot be `require`d.
@@ -313,9 +307,21 @@ export function readConfigs(
 
         return true;
       })
-      .map((root, projectIndex) =>
-        readConfig(argv, root, true, configPath, projectIndex),
-      );
+      .map((root, projectIndex) => {
+        // Skip on all except: projectIndex === 0, and isGlobalProject, and projects.length === 1
+        const skipArgvConfigOption = !(
+          projectIndex === 0 &&
+          isGlobalProject &&
+          projects.length === 1
+        );
+        return readConfig(
+          argv,
+          root,
+          skipArgvConfigOption,
+          configPath,
+          projectIndex,
+        );
+      });
 
     ensureNoDuplicateConfigs(parsedConfigs, projects);
     configs = parsedConfigs.map(({projectConfig}) => projectConfig);

packages/jest-core/src/cli/index.ts

@@ -34,6 +34,7 @@ type OnCompleteCallback = (results: AggregatedResult) => void;
 export const runCLI = async (
   argv: Config.Argv,
   projects: Array<Config.Path>,
+  isGlobalProject: boolean,
 ): Promise<{
   results: AggregatedResult;
   globalConfig: Config.GlobalConfig;
@@ -52,6 +53,7 @@ export const runCLI = async (
   const {globalConfig, configs, hasDeprecationWarnings} = readConfigs(
     argv,
     projects,
+    isGlobalProject,
   );
 
   if (argv.debug) {