Allowing two projects to inherit from the same bond

Question

Using Microsoft Bond in a C# project.

Suppose I had a Bond file A used in one project A', and wanted to have two projects B' and C' have Bond files B and C both of which have structs that inherit from a struct in file A. How would I do that?

I thought about making a ProjectReference, but it appears to only supply the C# classes generated from these Bond files, and not allow me to make Bond inheritance from the original Bond files, so instead I made a link between one project to the other. Unfortunately, my current solution is very error-prone, and changing that file location in one project would break the other as well.

What would be the suggested way to do that?

Answer 1

To have Bond files B and C inherit from or contain the types from Bond file A (in project A'), you need to import Bond file A at the top of B and C. This makes the types in A known in B and C.

a.bond

namespace A;

struct Base { }

b.bond

import "a.bond"

namespace B;

struct Derived : A.Base { } 

struct Composition {
    // notice fully qualified name is used for Base
    0: A.Base has_a_base;
}

For the import path, you have three options:

1. Use a fully qualified path like import "C:/src/projectAPrime/schemas/a.bond"
2. Use a relative path like import "../../projectAPrime/schemas/a.bond"
3. Use a relative path like import "a.bond" or import "schemas/a.bond" and add to the Bond import paths: elsewhere in the consuming project, you'd make sure that the BondImportDirectory item was augmented with a search directory for project A.

I would not recommend the first option, as it ties the paths to one specific machine's layout. Mixes of option 2 or 3 are used in practice.

For approach three, the consuming project usually has something like this either directly in it, or via some other MSBuild file it imports.

<ItemGroup>
  <BondImportDirectory Include="$(ProjectAPrimeRoot)" />
  <!-- or some other reference to project A, depending
       on how your projects are structured (perhaps you
       have a all_projects.props file for these sort of
       variables or item modifications -->
</ItemGroup>

I can't give you more concrete guidance than this, as your specific project structure isn't something I know, and MSBuild doesn't have a way for a project to "export" values that referencing project automatically get (that I'm aware of).

Note that you will still need a ProjectReference to project A', as the code generated in projects B' and C' will have dependencies on the code generated and compiled into the assembly that project A' produces.

For a working example of imports using BondImportDirectory see the C# import example in the Bond repository. This does not address the cross-project import, however, so you'll need to adapt for your situation.

If you're a C++ developer, this should feel similar to #include paths.