Implementation:DevExpress Testcafe StackCleaningHook

Knowledge Sources	DevExpress_Testcafe TestCafe Docs
Domains	Error Handling, Developer Experience
Last Updated	2026-02-12 12:00 GMT

Overview

stackCleaningHook is a singleton object that filters internal TestCafe frames from error stack traces so that users see only their own code in error output.

Description

src/errors/stack-cleaning-hook.js exports a default singleton object with an enabled property and a cleanError method. When enabled, it:

Increases the stack trace limit -- Sets Error.stackTraceLimit to 200 (from the original default, typically 10) because Babel-generated errors can produce very deep stacks. When disabled, it restores the original limit.
Parses error frames -- Uses the error-stack-parser library to parse the error's .stack string into structured StackFrame objects.
Strips existing trace lines -- _removeStackTraceLines walks the stack string from the bottom and removes all lines matching the /^\s+at\s+.*$/ pattern, leaving only the error message portion.
Filters internal frames -- Applies a stack filter (created by createStackFilter) that removes frames originating from internal TestCafe code, keeping only user-relevant frames up to the original stack trace limit.
Re-renders the stack -- Appends the filtered frames' source strings back onto the cleaned error.stack.

The enabled getter/setter uses a guard to avoid redundant state changes and manages the Error.stackTraceLimit toggle as a side effect.

Usage

The hook is enabled just before test file compilation/execution and disabled immediately after (in finally blocks). The APIBasedTestFileCompilerBase enables it around _compileCodeForTestFiles and _runCompiledCode, calling cleanError(err) on caught errors before re-throwing them as TestCompilationError.

Code Reference

Source Location

src/errors/stack-cleaning-hook.js (83 lines)

Signature

export default {
    isEnabled: false,

    _isStackTraceLine (stackLine): boolean,
    _removeStackTraceLines (error): void,
    _getFrames (error): StackFrame[],
    _renderFrameInfo (frames): string,

    get enabled (): boolean,
    set enabled (val: boolean): void,

    cleanError (error): Error,
};

Import

import stackCleaningHook from '../../errors/stack-cleaning-hook';

I/O Contract

Inputs

Parameter	Type	Description
`enabled` (setter)	`boolean`	Toggles the hook on/off. When set to `true`, increases `Error.stackTraceLimit` to 200. When set to `false`, restores the original limit.
`error` (for `cleanError`)	`Error`	An error object whose `.stack` property will be cleaned of internal TestCafe frames.

Outputs

Method	Return Type	Description
`cleanError(error)`	`Error`	Returns the same error object with its `.stack` property rewritten to contain only user-relevant stack frames. If the error has no parseable frames, it is returned unmodified.
`enabled` (getter)	`boolean`	Returns the current enabled state of the hook.

Usage Examples

Enabling around compilation:

import stackCleaningHook from '../../errors/stack-cleaning-hook';

stackCleaningHook.enabled = true;

try {
    const compiled = compiler._precompileCode(testFilesInfo);
    return compiled;
}
catch (err) {
    throw new TestCompilationError(stackCleaningHook.cleanError(err));
}
finally {
    stackCleaningHook.enabled = false;
}

Enabling around test execution:

stackCleaningHook.enabled = true;

try {
    await this._execAsModule(compiledCode, filename);
}
catch (err) {
    if (!(err instanceof APIError))
        throw new TestCompilationError(stackCleaningHook.cleanError(err));
    throw err;
}
finally {
    stackCleaningHook.enabled = false;
}

Related Pages

DevExpress_Testcafe_ApiBasedCompiler -- Primary consumer that enables/disables the hook during compilation and execution
DevExpress_Testcafe_ErrorTypes -- Defines the error codes for errors that get their stacks cleaned by this hook

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Principle

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