config command line option by ozcoder · Pull Request #295 · cloudflare/telescope

ozcoder · 2026-06-10T13:24:46Z

Added the command line option --config CONFIG_FILENAME. Command line options will override any options set in the configuration file.

I've moved some things around, in particular defaults are handled in executeTest. The URL to test can be in the configuration file or -u URL or as an argument to the command line.

Closes #62

…place. Read and parse the supplied configuration file. Due to the possibility of url being in the config file, I moved the checking. Do not let undefined values override earlier values. Added schemas for configuration file processing. Added associated types.

Moved URL checking around a bit. Allow config.url to be missing the protocol.

programmatic API does NOT partially auto-prefix. Emojis are not part of a valid URL. Just throw the error from normalizeUrlScheme.

nicjansma

Thanks for the PR @ozcoder! Would love to have this option.

nicjansma · 2026-07-06T02:02:05Z

+    }
+  } else if (engine === 'webkit') {
+    cfg.browser = 'safari';
+  } else { // chromium


Can you run npm run prettier on the project? I think some of these minor formatting consistency things will be auto-fixed.

nicjansma · 2026-07-06T02:03:16Z

+      throw err;
+    }
+
+    if (cfgStat.size > 4096) { // Arbitrary size


Any particular reason for blocking at > 4096 bytes?

I could see things like headers potentially grow above this.

Good point.
Arbitrary size, maybe 32K would be better. I was hoping for some guidance.

32K seems more reasonable.

What kind of situations do you think the size check will help with? People putting incorrect data in there for some reason? Unsure if we need the gate at all.

nicjansma · 2026-07-06T02:26:47Z

+    )
+    .addOption(
+      new Option(
+        '--config <string>',


Can you update README.md for the new --config option?

nicjansma · 2026-07-06T02:48:51Z

+
+  let cfg: LaunchOptions = { url: baseConfig.url || '' }; // Always required
+
+  if (baseConfig.options) {


It wasn't immediately obvious to me that the config JSON file should have a top-level options: {} key that all CLI options go into.

After looking at the original issue, I see that this comes from the results\xxx\config.json having a top-level options: {}.

Maybe this can be just documented clearly, with an example, in README.md?

Copilot

Pull request overview

This PR adds support for supplying a configuration file to Telescope via a new CLI option (--config <file>), and updates the option resolution flow so CLI flags override values from that config file. It also shifts where defaults are applied (into executeTest) and adjusts URL resolution to allow the URL to come from positional args, --url, or the config file.

Changes:

Add --config <file> CLI option and load base configuration from a JSON file.
Introduce Zod schemas/types for the config file shape and options loaded from it.
Refactor option/default merging and update a couple of programmatic/CLI tests.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 11 comments.

Show a summary per file

File	Description
packages/telescope/src/types.ts	Adds `config` option and new inferred types for config-file-related schemas.
packages/telescope/src/schemas.ts	Adds Zod schemas for config-file input and browser config/options blocks.
packages/telescope/src/index.ts	Adds `--config` flag, loads config in `launchTest`, and changes URL/default handling in `executeTest`.
packages/telescope/src/config.ts	Adds `getBaseConfig()` to parse config files and map them into `LaunchOptions`.
packages/telescope/tests/programmatic.test.ts	Updates programmatic URL/error handling expectations.
packages/telescope/tests/emulation.test.ts	Removes a test that asserted default browser selection in `normalizeCLIConfig`.

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ozcoder · 2026-07-10T05:59:44Z

 export async function launchTest(options: LaunchOptions): Promise<TestResult> {
  try {
-    return await executeTest(options);
+    const baseConfig = options.config ? getBaseConfig(options.config) : { url: '' };
+    return await executeTest(options, baseConfig);
  } catch (error) {


I need help creating a test. I'm not sure where the test config should live.

I think a clone of params.test.ts that focuses on the --config options would be nice. I haven't written tests for this project yet either! But if you have access to a coding agent, it could probably start with some boilerplate.

Increased max config file size to 32Kb. Do not use `any` during config copying. Do not need so many try/catches since they throw Errors anyways. Cleaned up comments. Copy the URL as-an-argument into options if existing. Some schemas can be a string or false, but not true. Better URL schema checking.

Updated emulation test to use resolveOptions.

nicjansma · 2026-07-29T18:04:14Z

-      ),
+      new Option(
+        '--disableJS',
+        `Disable JavaScript (default: ${DEFAULT_OPTIONS.disableJS})`)


Is there a reason some of the options use .default(xyz) and others describe the default in the description ... (default: xyz)?

nicjansma · 2026-07-29T18:12:31Z

Thanks for the updates @ozcoder! Lots of the changes look good.

Only a few outstanding things left:

Updates to README to describe --config
npm run prettier and npm run lint:fix
tests

Thanks!

ozcoder added 3 commits May 19, 2026 11:21

Merge branch 'main' into config-option

5901030

Moved URL checking around a bit. Allow config.url to be missing the protocol.

Defaults are handled in executeTest.

cfed902

programmatic API does NOT partially auto-prefix. Emojis are not part of a valid URL. Just throw the error from normalizeUrlScheme.

This was referenced Jun 10, 2026

Add an option to provide a config file. #62

Open

Test for malformed input URLs #289

Open

nicjansma requested changes Jul 6, 2026

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nicjansma reviewed Jul 6, 2026

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MildMax added the ticket This label indicates that internal ticket was created to track it. label Jul 6, 2026

sergeychernyshev requested a review from Copilot July 7, 2026 16:35

Copilot started reviewing on behalf of sergeychernyshev July 7, 2026 16:36 View session

Copilot AI reviewed Jul 7, 2026

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ozcoder added 3 commits July 9, 2026 22:09

Show defaults in help messaging.

c102d65

Split out merging configuration option into the function resolveOptions.

0652e77

Updated emulation test to use resolveOptions.

nicjansma reviewed Jul 29, 2026

View reviewed changes


		let cfg: LaunchOptions = { url: baseConfig.url \|\| '' }; // Always required

		if (baseConfig.options) {

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ozcoder commented Jun 10, 2026

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nicjansma commented Jul 29, 2026

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