# Feedback on documentation for installing headers with target\_sources(FILE\_SET)
**URL:** https://discourse.cmake.org/t/feedback-on-documentation-for-installing-headers-with-target-sources-file-set/6935
**Category:** Site Feedback
**Created:** [November 23, 2022, 9:02am UTC](https://discourse.cmake.org/t/feedback-on-documentation-for-installing-headers-with-target-sources-file-set/6935 "2022-11-23T09:02:31Z")
**Posts on this page:** 2
**Page:** 1
### Author:  [@josiest](https://discourse.cmake.org/u/josiest)
#### Post date: [November 23, 2022, 9:02am UTC](https://discourse.cmake.org/t/feedback-on-documentation-for-installing-headers-with-target-sources-file-set/6935/1 "2022-11-23T09:02:31Z")
I was looking at the documentation for [installing a directory](https://cmake.org/cmake/help/latest/command/install.html?#installing-files), and I noticed the note at the top of the section:
> **Note** If installing header files, consider using file sets defined by [`target_sources(FILE_SET)`](https://cmake.org/cmake/help/latest/command/target_sources.html#command:target_sources) instead. File sets associate headers with a target and they install as part of the target.
However there’s not a whole lot of examples of how to use this, and there are a few aspects of the existing documentation or occasional lack thereof that were a bit confusing to me or caused points of pain.
### Commonly used shorthand is not immediately apparent
Let’s consider the signature for `target_sources` under the [File Sets section](https://cmake.org/cmake/help/latest/command/target_sources.html#file-sets)
```auto
target_sources(
[
[FILE_SET [TYPE ] [BASE_DIRS ...] [FILES ...]]...
]...)
```
I was expecting that I’d need to do something like
`target_sources(my_target PUBLIC FILE_SET my_headers TYPE HEADERS ...)`, but I’d seen examples in the forum like, these two posts: [(1)](https://discourse.cmake.org/t/is-it-possible-to-retrieve-the-list-of-public-headers-when-using-target-sources-file-set-headers/5757) [(2)](https://discourse.cmake.org/t/cmake-file-set-for-header-when-using-destination/5692), that put `FILE_SET HEADERS` right next to each other. This was confusing because it was inconsistent with the documentation. That is, it was really easy to miss the note a lot further down in the documentation for the type parameter
> As a special case, if the name of the file set is one of the types, the type does not need to be specified and the `TYPE ` arguments can be omitted. For all other file set names, `TYPE` is required.
I think it would be helpful to have an example here toward the beginning of the documentation section that sets this precedent. It could even reference the existing tutorials:
`target_sources(MathFunctions PUBLIC FILE_SET HEADERS FILES MathFunctions.h)`
### Exporting a library with file sets requires additional parameters to install targets
Another pain point was that it doesn’t mention that when specifying the library targets for exporting (see the [exporting targets](https://github.com/aminya/project_options/issues/143) section of the importing and exporting guide), you also need to specify `FILE_SET HEADERS`. Continuing with the MathFunctions example, this would look like:
```auto
install(TARGETS MathFunctions
EXPORT MathFunctionsTargets
# ...
FILE_SET HEADERS
)
```
I was able to figure this out reasonably quickly by searching the error message I got and finding [this github issue](https://github.com/aminya/project_options/issues/143), but I think making this a note in the documentation for `target_sources` would be nice
### What happened to FILES\_MATCHING PATTERN?
This was a neat parameter from `install(DIRECTORY)` because it allowed you to glob all of your header files without creating a variable in the global namespace. `file(GLOB_RECURSE)` is also discouraged in the official documentation. Is there a better alternative than just to manually specify every single header file?
### What exactly does BASE\_DIRS do?
This is still unclear to me. The documentation for the parameter describes preconditions on the arguments passed to it, but it doesn’t really say what it’s used for. The only thing I could find was at the very bottom of the page.
> **INCLUDE\_DIRECTORIES** If the `TYPE` is `HEADERS` or `CXX_MODULE_HEADER_UNITS`, and the scope of the file set is `PRIVATE` or `PUBLIC`, all of the `BASE_DIRS` of the file set are wrapped in [`$`](https://cmake.org/cmake/help/latest/manual/cmake-generator-expressions.7.html#genex:BUILD_INTERFACE) and appended to this property.
This is also kind of unclear about what this means, but I’m wondering if this is the _only_ place `BASE_DIRS` is used, or if there’s a more well-defined description for what this parameter does?
---
### Author:  [@brad.king](https://discourse.cmake.org/u/brad.king)
#### Post date: [November 28, 2022, 6:40pm UTC](https://discourse.cmake.org/t/feedback-on-documentation-for-installing-headers-with-target-sources-file-set/6935/2 "2022-11-28T18:40:38Z")
@josiest thanks. This part of the forum is for feedback on the forum itself, or presentation issues on `cmake.org`. For feedback on CMake’s documentation proper, please use the [CMake Issue Tracker](https://gitlab.kitware.com/cmake/cmake/-/issues).