How tsconfig exclude pattern should actually work
  • 11-Jun-2023
Lightrun Team
Author Lightrun Team
How tsconfig exclude pattern should actually work

How tsconfig exclude pattern should actually work

Lightrun Team
Lightrun Team

Explanation of the problem

The issue at hand revolves around the behavior of exclude patterns in TypeScript, specifically when using the tsc --listFiles command. The problem arises when examining a directory structure containing nested node_modules folders and attempting to exclude certain files using patterns. The example structure consists of a top-level node_modules folder, a nested node_modules folder within a nested directory, and a deep-nested node_modules folder within a deep-nested directory. The exclusion patterns used include “node_modules”, “/node_modules”, “/node_modules”, and “/node_modules/“.

Upon analysis, the behavior of these patterns seems peculiar. In case 3, where the pattern is “**/node_modules”, it surprisingly excludes nothing. This result is unexpected, especially considering that case 2, using the pattern “*/node_modules”, successfully excludes the file /nested/node_modules/module/some.ts. The default behavior, when the exclude option is not specified, corresponds to case 1, which only excludes the file /node_modules/module/some.ts. However, one might argue that the default behavior should align with case 4, excluding node_modules in nested folders as well.

To comprehend the reasons behind this behavior and its implications, it is important to understand how TypeScript interprets and applies the exclude patterns during the file listing process. Analyzing the code base and examining the documentation could shed light on the specific implementation details of the exclude patterns. Additionally, considering the historical context of TypeScript versions (2.1.1 and nightly 2.2.0-dev.201xxxxx) used in the scenario might be relevant, as there could be changes or improvements in subsequent versions that affect the behavior of the exclude patterns. Further investigation into the TypeScript source code and related discussions in the TypeScript community could provide insights into the rationale behind the observed behavior and whether it aligns with the expected behavior for exclude patterns.


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Problem solution for How tsconfig exclude pattern should actually work

The responses to the question express a common sentiment regarding the behavior of exclude patterns in TypeScript. While the default exclude pattern provided by TypeScript effectively excludes the three most common package manager folders (node_modules, bower_components, jspm_modules), there is a suggestion that the default behavior should extend to nested folders as well. This would entail including nested node_modules folders in the exclusion process. The reasoning behind this suggestion is that if TypeScript is capable of intelligently excluding the most common package manager folders, it should also be capable of extending this behavior to encompass nested folders.

Another point raised in the discussion pertains to the default exclusion pattern used by TypeScript. Currently, the default pattern is specified as “node_modules/“, but there is a question about whether it should be “/node_modules/” instead. This discrepancy prompts a consideration of whether the default behavior should exclude the top-level node_modules folder (“/node_modules/*”) rather than only excluding files within the node_modules folder at the same level as the TypeScript files. It is argued that this change could provide more intuitive and comprehensive exclusion capabilities, aligning with the expectations of developers.

In response to these observations, it is noted that the defaults provided by TypeScript are not intended to be exhaustive or all-encompassing. They serve as a starting point to cover the needs of most users. However, developers have the flexibility to define their own exclude patterns to augment the default behavior. By defining custom exclude patterns, developers can tailor the exclusion process according to their specific requirements. This approach allows for greater control and customization while still leveraging the functionality provided by TypeScript.

Other popular problems with Microsoft TypeScript

Problem: Incorrect Use of TypeScript Interfaces

TypeScript interfaces are a powerful tool for enforcing strict type checking in a codebase. However, incorrect use of interfaces can lead to problems with code accuracy and maintainability. For example, if an interface is defined with properties that are not used elsewhere in the code, it can be difficult to track down the source of an error later on.


To avoid this problem, it is recommended to make use of strict null checking and optional properties in interfaces. Additionally, be mindful of the properties and methods defined in an interface, and make sure that they are actually used elsewhere in the code. If an interface is no longer needed, it should be removed to prevent confusion and errors.

Problem: TypeScript Compilation Errors

TypeScript is a statically-typed language, which means that all type information is known at compile time. This can lead to compilation errors when code is written that violates TypeScript’s type system. For example, if a variable is declared with a type of string, and an attempt is made to assign a value of type number to it, a compile-time error will occur.


To resolve TypeScript compilation errors, it is important to carefully review the code and make sure that all variables are correctly declared with the correct type. In cases where a variable needs to be used with different types, a union type can be used to specify multiple types for the same variable. Additionally, the TypeScript documentation provides detailed information about the type system, and can be a valuable resource for resolving compilation errors.

Problem: Managing TypeScript Dependencies

Managing dependencies in a TypeScript project can be challenging, as different libraries and packages may have different versions and compatibility requirements. This can lead to conflicts and errors when attempting to use multiple libraries that have incompatible dependencies.


To resolve dependency management issues in a TypeScript project, it is recommended to make use of a package manager such as npm or yarn. These tools provide automated dependency management, and can help to prevent conflicts and errors when using multiple libraries and packages. Additionally, it is important to keep dependencies up-to-date, as newer versions may resolve compatibility issues and improve the overall stability of the project.

A brief introduction to Microsoft TypeScript

Microsoft TypeScript is a statically-typed, open-source programming language that builds on JavaScript. It is designed to provide optional type safety, improved tooling, and enhanced scalability to JavaScript code. TypeScript offers a language structure that is familiar to JavaScript developers, but with the added benefits of static type checking and enhanced tooling support.

TypeScript is designed to be compatible with existing JavaScript code and integrates seamlessly into many popular development environments and build tools. The language offers features such as class and interface definitions, type inference, and advanced type checking, making it easier for developers to write robust, maintainable code. TypeScript also includes a transpiler that can convert TypeScript code into equivalent JavaScript code, allowing developers to write TypeScript code that can run in any environment that supports JavaScript.

Most popular use cases for Microsoft TypeScript

  1. Large-scale web application development: TypeScript is well-suited for developing large-scale web applications, as it provides developers with the ability to write scalable, maintainable code. With its optional type checking, developers can catch type-related errors at compile time, making it easier to catch bugs and reduce the time spent debugging code. Additionally, TypeScript’s compatibility with existing JavaScript code allows developers to gradually adopt the language in their existing codebases, making it easier to transition to a statically-typed codebase.
class User {
    name: string;
    email: string;

    constructor(name: string, email: string) { = name; = email;

const user = new User("John Doe", "");
  1. Improved tooling support: TypeScript integrates well with modern development environments and build tools, making it easier for developers to write, manage, and maintain code. With TypeScript’s enhanced tooling support, developers can benefit from features such as code completion, refactoring, and debugging, which can help to increase developer productivity and reduce the time spent on manual code management tasks.
  2. Interoperability with JavaScript libraries: TypeScript is designed to be compatible with existing JavaScript code, making it easy for developers to integrate TypeScript with existing JavaScript libraries and codebases. Additionally, TypeScript provides a way to define type information for JavaScript libraries, making it easier to write TypeScript code that interacts with existing JavaScript libraries in a type-safe manner. This can help to reduce the time spent debugging and improve the overall stability of code.

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