Dependency ... not found in module

Question

I'm using opencv in my qt project, and I want to link it. But th qbs for my project does not find my opencv module. Here is my file structure:

MyProject/
├── build/
├── opencv/
│ ├── debug/
│ │ └── include/, lib/
│ ├── release/
│ │ └── include/, lib/
│ └── opencv.qbs
├── src/
│ └── main.cpp
└── MyProject.qbs <-- Main project file

Here is my opencv.qbs file :

import qbs.FileInfo
Module {
 name: "opencv"
 Export {
 Depends { name: "cpp" }
 cpp.includePaths: qbs.buildVariant == "release" ? "release/include" : "debug/include"
 cpp.libraryPaths: qbs.buildVariant == "release" ? "release/lib" : "debug/lib"
 cpp.dynamicLibraries: qbs.buildVariant == "release" ? [...files...] : [...filesd...]
 }
}

And here is MyProject.qbs:

import qbs.FileInfo
QtApplication {
 Depends { name: "Qt.widgets" }
 Depends { name: "opencv" }
 cpp.defines: [
 // You can make your code fail to compile if it uses deprecated APIs.
 // In order to do so, uncomment the following line.
 //"QT_DISABLE_DEPRECATED_BEFORE=0x060000" // disables all the APIs deprecated before Qt 6.0.0
 ]
 files: [
 "src/**",
 ]
 references: [ "opencv/opencv.qbs" ]
 install: true
 installDir: qbs.targetOS.contains("qnx") ? FileInfo.joinPaths("/tmp", name, "bin") : base
}

the line Depends { name: "opencv" } is flagged Dependency 'opencv' not found for product 'deconv'.

Answer 1

The two problems here are:

• You do not pull in modules via "references" like products; instead, they are looked up via the module search paths; see https://doc.qt.io/qbs/custom-modules.html.

• Modules cannot contain Export items. All the property bindings in a module are "exported" automatically to the depending product.

• You don't set a module's name explicitly; it is derived from the location (see above).

In fact, referencing a module item this way triggers an error:

ERROR: Item type should be 'Product' or 'Project', but is 'Module'.

So I suspect your actual project doesn't quite look like what you pasted here.

Note that alternatively, you can use your layout as is by changing the Module to a Product (the Export item also creates a module).

• Sheed: My project is exactly as presented, however after reviewing your answer and tweaking with another clean project (which wasn't that different, it simply didn't have as many lib/include/bin files) I had to do the following : Change Module to Product, and in the top-level .qbs, pack QtApplication in the scope of Project and pull the "references" property above (and out of) QtApplication. Honestly QtCreator compile errors could be a LOT more explanatory. But thank you for your comment
• Christian Kandeler: Oops, I overlooked that the "references" was on the product level. I'll see whether we can throw an error for that.

Answer 2

As it turns out, and it's not made clearly in the documentation, if you want to link or add an external library, you should pack the importing application into a Project and reference your library from that Project and not from the application:

Project {
 references: [ "opencv/opencv.qbs" ] // OK
 QtApplication {
 Depends { name: "opencv" }
 // references: [ "opencv/opencv.qbs" ] // WRONG
 }
}

If you want to import external resources, these should be placed in a Product with the exported include/binaries/lib files:

Product {
 name: "opencv"
 Export {
 Depends { name: "cpp" }
 cpp.includePaths: ...
 cpp.libraryPaths: ...
 cpp.dynamicLibraries: ...
 }
}

Or from my understanding, use a Module only if it is globally shared (e.g needs to be in your %appdata% folder in Windows) or locally, see Christian Kandeler's answer for more information.