advice on best practices for transitive dependencies

Development Package Manager
1

Hello,

I have a question regarding best practices for transitive dependencies.
Suppose I have package A, that depends on (uses classes from) package B
and package C. Package B also depends on package C.

For package A, I have to specify dependency on package B. Should I also
specify dependency on package C, if I know for sure that package B depends
on package C, so package C will be fetched by SwiftPM anyway.

Vadim Eisenberg

2

Hello,

I have a question regarding best practices for transitive dependencies.
Suppose I have package A, that depends on (uses classes from) package B
and package C. Package B also depends on package C.

For package A, I have to specify dependency on package B. Should I also
specify dependency on package C, if I know for sure that package B depends
on package C, so package C will be fetched by SwiftPM anyway.

You should only specify the dependencies on packages you directly want to use.
So, if your package A wants to use classes from B but not from C and B depends on C
then you shouldn't specify C as dependency in A. But in this case you should never use
any of the classes defined in C from package A— this is something we'd like to enforce but can't at the moment.

···

On 08-Dec-2016, at 7:40 PM, Vadim Eisenberg via swift-build-dev <swift-build-dev@swift.org> wrote:

Vadim Eisenberg

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3

Ankit, let me rephrase the question. I will use term "package X directly
depends on package Y, if package X uses classes defined in package Y. So
the rephrased question is:

Suppose I have package A, that directly depends on both package B and
package C. Package B directly depends on package C.

For package A, I have to specify dependency on package B. Should I also
specify dependency on package C in package A, if I know for sure that
package B depends on package C, so package C will be fetched by SwiftPM
anyway.

Vadim Eisenberg

···

From: Ankit Aggarwal <ankit_aggarwal@apple.com>
To: Vadim Eisenberg/Haifa/IBM@IBMIL
Cc: swift-build-dev@swift.org
Date: 12/08/2016 04:18 PM
Subject: Re: [swift-build-dev] advice on best practices for
transitive dependencies
Sent by: ankit_aggarwal@apple.com

On 08-Dec-2016, at 7:40 PM, Vadim Eisenberg via swift-build-dev <swift-build-dev@swift.org> wrote:

Hello,

I have a question regarding best practices for transitive dependencies.
Suppose I have package A, that depends on (uses classes from) package B
and package C. Package B also depends on package C.

For package A, I have to specify dependency on package B. Should I also
specify dependency on package C, if I know for sure that package B

depends

on package C, so package C will be fetched by SwiftPM anyway.

You should only specify the dependencies on packages you directly want to
use.
So, if your package A wants to use classes from B but not from C and B
depends on C
then you shouldn't specify C as dependency in A. But in this case you
should never use
any of the classes defined in C from package A? this is something we'd
like to enforce but can't at the moment.

Vadim Eisenberg

_______________________________________________
swift-build-dev mailing list
swift-build-dev@swift.org
https://lists.swift.org/mailman/listinfo/swift-build-dev

4

Ankit, let me rephrase the question. I will use term "package X directly
depends on package Y, if package X uses classes defined in package Y. So
the rephrased question is:

Suppose I have package A, that directly depends on both package B and
package C. Package B directly depends on package C.

For package A, I have to specify dependency on package B. Should I also
specify dependency on package C in package A, if I know for sure that
package B depends on package C, so package C will be fetched by SwiftPM
anyway.

Yup you should definitely specify both B and C in A because even though you know B depends on C in this version it might not in next. And as I said if SwiftPM were to ever enforce this behaviour using Swift compiler A will not able to use symbols from C because it doesn't directly depend on it.

···

On 08-Dec-2016, at 8:00 PM, Vadim Eisenberg <VADIME@il.ibm.com> wrote:

Vadim Eisenberg

From: Ankit Aggarwal <ankit_aggarwal@apple.com>
To: Vadim Eisenberg/Haifa/IBM@IBMIL
Cc: swift-build-dev@swift.org
Date: 12/08/2016 04:18 PM
Subject: Re: [swift-build-dev] advice on best practices for
transitive dependencies
Sent by: ankit_aggarwal@apple.com

On 08-Dec-2016, at 7:40 PM, Vadim Eisenberg via swift-build-dev > <swift-build-dev@swift.org> wrote:

Hello,

I have a question regarding best practices for transitive dependencies.
Suppose I have package A, that depends on (uses classes from) package B
and package C. Package B also depends on package C.

For package A, I have to specify dependency on package B. Should I also
specify dependency on package C, if I know for sure that package B

depends

on package C, so package C will be fetched by SwiftPM anyway.

You should only specify the dependencies on packages you directly want to
use.
So, if your package A wants to use classes from B but not from C and B
depends on C
then you shouldn't specify C as dependency in A. But in this case you
should never use
any of the classes defined in C from package A? this is something we'd
like to enforce but can't at the moment.

Vadim Eisenberg

_______________________________________________
swift-build-dev mailing list
swift-build-dev@swift.org
https://lists.swift.org/mailman/listinfo/swift-build-dev

5

Thanks, Ankit!

From your answer: "if SwiftPM were to ever enforce this behaviour using

Swift compiler A will not able to use symbols from C because it doesn't
directly depend on it.", I understand that even if package B is called
CAdapter, and its sole purpose is to adapt C package to A, A still should
specify dependency on both CAdapter and C, if it uses classes directly
from CAdapter and C, despite being 100% sure that CAdapter will always
depend on C.

Best Regards,
Vadim Eisenberg

···

From: Ankit Aggarwal <ankit_aggarwal@apple.com>
To: Vadim Eisenberg/Haifa/IBM@IBMIL
Cc: swift-build-dev@swift.org
Date: 12/08/2016 04:37 PM
Subject: Re: [swift-build-dev] advice on best practices for
transitive dependencies
Sent by: ankit_aggarwal@apple.com

On 08-Dec-2016, at 8:00 PM, Vadim Eisenberg <VADIME@il.ibm.com> wrote:

Ankit, let me rephrase the question. I will use term "package X directly

depends on package Y, if package X uses classes defined in package Y. So

the rephrased question is:

Suppose I have package A, that directly depends on both package B and
package C. Package B directly depends on package C.

For package A, I have to specify dependency on package B. Should I also
specify dependency on package C in package A, if I know for sure that
package B depends on package C, so package C will be fetched by SwiftPM
anyway.

Yup you should definitely specify both B and C in A because even though
you know B depends on C in this version it might not in next. And as I
said if SwiftPM were to ever enforce this behaviour using Swift compiler A
will not able to use symbols from C because it doesn't directly depend on
it.

Vadim Eisenberg

From: Ankit Aggarwal <ankit_aggarwal@apple.com>
To: Vadim Eisenberg/Haifa/IBM@IBMIL
Cc: swift-build-dev@swift.org
Date: 12/08/2016 04:18 PM
Subject: Re: [swift-build-dev] advice on best practices for
transitive dependencies
Sent by: ankit_aggarwal@apple.com

On 08-Dec-2016, at 7:40 PM, Vadim Eisenberg via swift-build-dev > <swift-build-dev@swift.org> wrote:

Hello,

I have a question regarding best practices for transitive dependencies.

Suppose I have package A, that depends on (uses classes from) package B

and package C. Package B also depends on package C.

For package A, I have to specify dependency on package B. Should I also

specify dependency on package C, if I know for sure that package B

depends

on package C, so package C will be fetched by SwiftPM anyway.

You should only specify the dependencies on packages you directly want

to

use.
So, if your package A wants to use classes from B but not from C and B
depends on C
then you shouldn't specify C as dependency in A. But in this case you
should never use
any of the classes defined in C from package A? this is something we'd

like to enforce but can't at the moment.

Vadim Eisenberg

_______________________________________________
swift-build-dev mailing list
swift-build-dev@swift.org
https://lists.swift.org/mailman/listinfo/swift-build-dev