[vcpkg]"default-features":false seems to just be ignored. Feature selection always adds default-features

[Arech]

Describe the bug
I might misunderstand something in vcpkg, but I though that according to the docs, "default-features": false should totally disable default feature set defined for a port and install only explicitly selected features. But it's not the case. Default-features are always selected and installed.

I have a private repository containing two ports:

• X with two features: heavyA and lightB, and "default-features": [ "heavyA" ].
• Y with several features, one of which, say "featureB" has

"dependencies": [
  {
    "name": "X",
    "default-features": false,
    "features": [ "lightB" ]
  }
]

I assumed that when manifest contains a dependency on port Y[featureB], then vcpkg must also install port X with feature lightB only, b/c default features, containing heavyA, are disabled. However, when building a software I noticed that port X installs both features, - heavyA (that should be disabled) and lightB. I've double checked everything and I can't find any potential source of dependency on feature heavyA of port X anywhere.

I was able to replicate that with publicly available ports:
opencv4 port contains a spectra of default-enabled features.

vcpkg depend-info opencv4
...
opencv4[default-features, webp, jpeg, dnn, png, quirc, tiff]: libjpeg-turbo, libpng, libwebp, ....

opencv4 has ffmpeg feature defined in a similar manner with restricted feature set:

 "ffmpeg": {
      "description": "ffmpeg support for opencv",
      "dependencies": [
        {
          "name": "ffmpeg",
          "default-features": false,
          "features": [
            "avcodec",
            "avformat",
            "swresample",
            "swscale"
          ]
        }
      ]
    },

By default ffmpeg port has these default features:

 "default-features": [
    "avcodec",
    "avdevice",
    "avfilter",
    "avformat",
    "swresample",
    "swscale"
  ],

So I assume that when I install opencv4[ffmpeg] only 4 specifically selected by opencv4 manifest's features must be present. However, it's not true:

vcpkg depend-info opencv4[ffmpeg]
...
ffmpeg[avfilter, avdevice, avcodec, avformat, swresample, swscale]: ......
...
opencv4[default-features, jpeg, dnn, ffmpeg, png, quirc, tiff, webp]: ffmpeg,  libjpeg-turbo, libpng, libwebp, ......

i.e. vcpkg fetches all default features for ffmpeg plus those additionally specified, and for opencv4 it also selects all default features plus ffmpeg feature as an addition, instead of using it exclusively.
(depend-info command is used to demonstrate the issue, the same is happening when vcpkg really install ports)

This seems like a bug to me. Documentation clearly states:

If the user wants to explicitly disable the default features, they can do so by adding "default-features": false to the dependency:

(see the bottom of the page)

Do I misunderstand something?

Environment
The same results in Windows 10:

>vcpkg --version
vcpkg package management program version 2023-11-16-4c1df40a3c5c5e18de299a99e9accb03c2a82e1e

>git log -1
commit b051c80d93fb023ce959622271e1183bff291fd5 (HEAD -> master, origin/master, origin/HEAD)
Author: ...
Date:   Wed Dec 6 03:41:09 2023 +0800

as well as on Ubuntu20.04 (in WSL with own vcpkg checkout, which hardly matters..)

$ ./vcpkg --version
vcpkg package management program version 2023-11-16-4c1df40a3c5c5e18de299a99e9accb03c2a82e1e

$ git log -1
commit e85cafa30def190eca0dc1413bf8c04e434af567 (HEAD -> master, origin/master, origin/HEAD)
Author: ...
Date:   Thu Nov 30 13:58:50 2023 -0800

[Neumann-A]

"default-features": false just means the port does not depend on the default features it does not say that you do not want default features. If you do not want default features you need to explicitly say so on the command line or within or projects manifest. If a port is transitively pulled in you also need to mention that port and say you don't want the default features of that.

[Arech]

Thanks for the reply, Alexander

"default-features": false just means the port does not depend on the default features it does not say that you do not want default features.

I'm not an English language expert and not a native speaker, but to me if that's correct, then the docs with "If the user wants to explicitly disable the default features, they can do so by adding "default-features": false" is misleading. Or at least semantic of "default-feautures" is different for app manifest file (where it disables them indeed), and for ports (where it means something else).
Can that be documented?

If a port is transitively pulled in you also need to mention that port and say you don't want the default features of that.

Do I get you right, that if I want opencv4[ffmpeg] to install only 4 features it needs (that are explicitly listed in opencv4 port manifest) instead of 6 default, I should manually specify dependency on ffmpeg in my app's manifest with these 4 features? So I basically should depend on opencv4 port internal implementation and must also freeze it's version?

[Neumann-A]

, I should manually specify dependency on ffmpeg in my app's manifest with these 4 features?

It is enough to say you want ffmpeg with "default-features": false . The other features will be pulled in by opencv4 since they are required by it.

Also there is nothing more to document. The docs already say:

Default features are a set of features to be automatically activated if the top-level project does not explicitly request a build without them

[FrankXie05]

@Arech In actual testing, this function is normal and it does disable the build of the default features.
But there is currently a problem: the installation log incorrectly displays the default features.

[FrankXie05]

vcpkg/ports/tinyorm/vcpkg.json

Line 31 in 50bffcc

"default-features": [

{ORM} was not passed to install the feature orm.

[dg0yt]

at least semantic of "default-features" is different for app manifest file (where it disables them indeed), and for ports (where it means something else).

This is right. In port manifests, it declares a possibility and enables user choice. The actual control is only in user project manifests (or at the command line using pseudo feature core).

[Arech]

That's a bit confusing... I think I haven't seen that difference mentioned in ports creation documentation, but now I understand it better. Probably should be said somewhere more explicitly...

Anyway, thanks a lot everyone involved and have a great weekend!

[Arech]

(and a personal thanks to @FrankXie05 for spotting the issue)

[FrankXie05]

Currently, I can confirm that this feature is indeed broken. (either from the configuration parameters passed or the actual installed dependencies).

When default-features is false, the installation dependencies of default-features will not be prohibited at all.

@JavierMatosD @BillyONeal Could you please help take a look?

[dg0yt]

Currently, I can confirm that this feature is indeed broken. (either from the configuration parameters passed or the actual installed dependencies).

When default-features is false, the installation dependencies of default-features will not be prohibited at all.

@FrankXie05 please explain what is broken, given the expected behavior presented in
#35694 (comment),
#35694 (comment),
#35694 (comment).

[Arech]

Erm... Here's another test that shows that default-features: false works in a strange way even in an application manifest:

App manifest file explicitly prohibits default-features of opencv4 port and explicitly lists only jpeg feature that depends only on libjpeg-turbo.

{
  "$schema": "https://raw.githubusercontent.com/microsoft/vcpkg-tool/main/docs/vcpkg.schema.json",
  "name": "myapp",
  "version": "1",
  "vcpkg-configuration": {
    "$schema": "https://raw.githubusercontent.com/microsoft/vcpkg-tool/main/docs/vcpkg-configuration.schema.json",
    "default-registry": {
      "kind": "git",
      "repository": "https://github.com/microsoft/vcpkg",
      "baseline": "000d1bda1ffa95a73e0b40334fa4103d6f4d3d48"
    }
  },
  "features": {
    "common-opencv-port": {
      "description": "A single common for the whole repo port of OpenCV",
      "dependencies": [
        {
          "name": "opencv4",
          "default-features": false,
          "features": [ "jpeg" ]
        }
      ]
    },

    "irrelevant-feature": {
      "description": "heavy ports just for testing, they shouldn't be used",
      "dependencies": [ "opencv3", "opencv2" ]
    },

    "myfeature": {
      "description": "will use this feature only. common-opencv-port might be a dependency of many other features of this app",
      "dependencies": [
        {
          "name": "myapp",
          "default-features": false,
          "features": [ "common-opencv-port" ]
        }
      ]
    }
  },
  "dependencies": []
}

CMakeLists.txt to choose which feature to use depending on build settings

cmake_minimum_required(VERSION 3.16)
# choosing feature list (depending on some CMake vars in a real project)..
set(VCPKG_MANIFEST_FEATURES "myfeature")
# trigger vcpkg
project(MyTestProj)

I expect it to use only `"jpeg" feature of OpenCV4 port.

Now run and observe what vcpkg starts to build:

$ rm -rf ./build;cmake -B ./build -G Ninja -DCMAKE_TOOLCHAIN_FILE=$VCPKG_ROOT/scripts/buildsystems/vcpkg.cmake
-- Running vcpkg install
warning: Embedding `vcpkg-configuration` in a manifest file is an EXPERIMENTAL feature.
Fetching registry information from https://github.com/microsoft/vcpkg (HEAD)...
Detecting compiler hash for triplet x64-windows...
The following packages will be built and installed:
  * flatbuffers:x64-windows@23.5.26#1 -- ...\vcpkg\registries\git-trees\2f827d9a5f37614af7cdb44c15075dbaac88d740
  * libjpeg-turbo:x64-windows@3.0.1 -- ...\vcpkg\registries\git-trees\481b08127d4002ba7441f144df259e03271e7592
  * liblzma:x64-windows@5.4.4 -- ...\vcpkg\registries\git-trees\f285b7c4ffa2cc065c7c6fec4b61006f7fa2714e
  * libpng:x64-windows@1.6.40 -- ...\vcpkg\registries\git-trees\1a2a7f489e57c9e55e049b7c5f0a28c8ff4464ed
  * libwebp[core,libwebpmux,nearlossless,simd,unicode]:x64-windows@1.3.2 -- ...\vcpkg\registries\git-trees\0b981028589375097039d5e39e7d87659cdfa824
  * opencv4[core,default-features,dnn,jpeg,png,quirc,tiff,webp]:x64-windows@4.8.0#12 -- ...\vcpkg\registries\git-trees\c3d46b66df37511cf7b49ceffe96f5ff62acf6ea
  * protobuf:x64-windows@3.21.12 -- ...\vcpkg\registries\git-trees\3b145508ba614fe26989b23f6317f15bf6467be4
  * quirc:x64-windows@1.1#3 -- ...\vcpkg\registries\git-trees\85b17d675bbbb05448d16af79d434bc5fca51f7b
  * tiff[core,jpeg,lzma,zip]:x64-windows@4.6.0#1 -- ...\vcpkg\registries\git-trees\1c0fc716f916833234f0fb5e7061d52e9063e7c6
  * vcpkg-cmake:x64-windows@2023-05-04 -- ...\vcpkg\registries\git-trees\88a7058fc7fa73a9c4c99cfcae9d79e2abf87a5a
  * vcpkg-cmake-config:x64-windows@2022-02-06#1 -- ...\vcpkg\registries\git-trees\8d54cc4f487d51b655abec5f9c9c3f86ca83311f
  * vcpkg-get-python-packages:x64-windows@2023-07-28 -- ...\vcpkg\registries\git-trees\80e0cf9d38d72126b34eb1ee9b33f936c778a696
  * zlib:x64-windows@1.3 -- ...\vcpkg\registries\git-trees\5ac18c6e6e3e2bf5a9e3d0bc8a845f198e4c4e05
Additional packages (*) will be modified to complete this operation.
......

vcpkg ignores requirement to use only explicitly specified features and use all defaults instead. And it's not that it shows it wrongly, it really starts to build every other damn feature I don't need.

$ $VCPKG_ROOT/vcpkg.exe --version
vcpkg package management program version 2023-12-12-1c9ec1978a6b0c2b39c9e9554a96e3e275f7556e

$ cmake --version
cmake version 3.27.2-msvc1

The same behavior I see on Ubuntu 20.04 @ WSL

$ $VCPKG_ROOT/vcpkg --version
vcpkg package management program version 2023-12-12-1c9ec1978a6b0c2b39c9e9554a96e3e275f7556e

$ cmake --version
cmake version 3.25.1

You can clone https://github.com/Arech/vcpkg_default_features repo with that code

If I'm doing something wrong here, please advice me on how to modify the code to make it only use explicitly specified features? Current behavior brings enormous toll on our CI and on local devs...