Add debug hint for new users

config.js

@@ -418,7 +418,7 @@ async function readConfigFile(configDir, env) {
 }
 
 /**
- * @typedef {{no_external_locking?: boolean, no_locking?: boolean, locking_verbose?: boolean, external_locking_client?: string, external_locking_url?: string, expect_nothing?: boolean}} Config
+ * @typedef {{no_external_locking?: boolean, no_locking?: boolean, locking_verbose?: boolean, external_locking_client?: string, external_locking_url?: string, expect_nothing?: boolean, filter?: RegExp, forward_console?: boolean, keep_open?: boolean}} Config
  */
 
 /**

main.js

@@ -99,6 +99,7 @@ async function real_main(options={}) {
         if (!test_info) return;
 
         results = render.craftResults(config, test_info);
+        console.log(test_info);
     }
 
     await render.doRender(config, results);

output.js

@@ -195,7 +195,11 @@ function resultSummary(config, tasks, onTests=false) {
     return res;
 }
 
-
+/**
+ * @param {import('./config').Config} config
+ * @param {import('./runner').RunnerState} state
+ * @private
+ */
 function finish(config, state) {
     last_state = null;
     const {tasks} = state;
@@ -213,10 +217,31 @@ function finish(config, state) {
     print(resultSummary(config, tasks) + '\n');
 
     const expectedToFail = tasks.filter(t => t.expectedToFail && t.status === 'error');
+
+    let hasHint = false;
     if (!config.expect_nothing && (expectedToFail.length > 0)) {
-        let msg = color(config, 'gray', '  Pass in -E/--expect-nothing to ignore expectedToFail declarations.');
-        msg += '\n\n';
-        print(msg);
+        const msg = color(config, 'gray', '  Pass in -E/--expect-nothing to ignore expectedToFail declarations.');
+        print(msg + '\n');
+        hasHint = true;
+    }
+    const hasDebug = config.debug || config.forward_console || config.keep_open || config.devtools || config.devtools_preserve;
+    if ((!config.filter || !hasDebug) && utils.count(tasks, t => t.status === 'error' && (!t.expectedToFail || config.expect_nothing)) > 0) {
+        let msg = '';
+        if (!config.filter && !hasDebug) {
+            msg = '  Pass in -f/--filter REGEX and -d/--debug to inspect specific tests.';
+        } else if (!config.filter) {
+            msg = '  Pass in -f/--filter REGEX to inspect specific tests.';
+        } else if (!hasDebug) {
+            msg = '  Pass in -d/--debug to inspect tests.';
+        }
+
+        if (msg) {
+            print(color(config, 'gray', msg) + '\n');
+            hasHint = true;
+        }
+    }
+    if (hasHint) {
+        print('\n');
     }
 
     // Internal self-check

tests/debug_tests/config/local.json

@@ -0,0 +1 @@
+{}

tests/debug_tests/run

@@ -0,0 +1,8 @@
+#!/usr/bin/env node
+
+const pentf = require('../../index.js');
+
+pentf.main({
+    rootDir: __dirname,
+    testsDir: __dirname,
+});

tests/debug_tests/test.js

@@ -0,0 +1,8 @@
+async function run() {
+    throw new Error('fail');
+}
+
+module.exports = {
+    run,
+    description: 'fail'
+};

tests/selftest_debug_hint.js

@@ -0,0 +1,39 @@
+const assert = require('assert').strict;
+const path = require('path');
+const child_process = require('child_process');
+
+async function run() {
+    // Run in subprocess so that handle exhaustion does not affect this process
+    const sub_run = path.join(__dirname, 'debug_tests', 'run');
+
+    async function runPentf(...args) {
+        return await new Promise((resolve, reject) => {
+            child_process.execFile(
+                sub_run,
+                ['--exit-zero', '--no-screenshots', ...args],
+                (err, stdout, stderr) => {
+                    if (err) reject(err);
+                    else resolve({stdout, stderr});
+                }
+            );
+        });
+    }
+
+    let stderr = (await runPentf()).stderr;
+    assert(/Pass in -f\/--filter REGEX and -d\/--debug to inspect specific tests/.test(stderr));
+
+    // stderr = (await runPentf('-d')).stderr;
+    // assert(/Pass in -f\/--filter REGEX to inspect specific tests/.test(stderr));
+
+    // stderr = (await runPentf('-f test')).stderr;
+    // assert(/Pass in -d\/--debug to inspect tests/.test(stderr));
+
+    // stderr = (await runPentf('-f test -d')).stderr;
+    // assert(!/Pass in/.test(stderr));
+}
+
+module.exports = {
+    description: 'Display debug hints',
+    resources: [],
+    run,
+};

utils.js

@@ -91,6 +91,11 @@ function arange(count) {
     return Array.from(range(count));
 }
 
+/**
+ * @template T
+ * @param {T[]} ar
+ * @param {(item: T) => boolean} filter
+ */
 function count(ar, filter) {
     let res = 0;
     for (var el of ar) {