How do i reference a specific file in a genrule

[kv]

genrule(

     name = "abc",

     srcs =[ "@com_xyc//:spits2filesasoutput"], #<---- this rule gives me 2 files, fn.txt, otherfn.txt

     outs = ["newnamefn.log"],

     cmd = """

     mv $(locations @com_xyc//:spits2filesasoutput) $@

     """

)

I just want to rename otherfn.txt to newnamefn.log. How do I reference that specific file from the srcs?

Thanks

kv

[Alex Garcia]

$(location otherfn.txt) should work

Alexandre Garcia Mayans

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[kv]

in cmd attribute of genrule rule //:abc: label '//:otherfn.txt' in $(location) expression is not a declared prerequisite of this rule

I'm getting this error. What am I missing?

On Thursday, March 19, 2020 at 3:18:06 PM UTC-7, Alex Garcia wrote:

$(location otherfn.txt) should work

Alexandre Garcia Mayans

On 19 Mar 2020, 23:15 +0100, kv <vijay....@gmail.com>, wrote:

genrule(

     name = "abc",

     srcs =[ "@com_xyc//:spits2filesasoutput"], #<---- this rule gives me 2 files, fn.txt, otherfn.txt

     outs = ["newnamefn.log"],

     cmd = """

     mv $(locations @com_xyc//:spits2filesasoutput) $@

     """

)

I just want to rename otherfn.txt to newnamefn.log. How do I reference that specific file from the srcs?

Thanks

kv

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[Alex Garcia Mayans]

$(location @com_xyc//:otherfn.txt) maybe ?

Regards,

Alexandre Garcia Mayans

On 19 Mar 2020, at 23:40, kv <vijay.k...@gmail.com> wrote:



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[Alex Humesky]

$(location) requires a label, and only some outputs of a rule have labels (these are the "implicit outputs" of a rule, e.g. for a java_binary named "bar" in a package named "foo", there are the labels "//foo:bar" and "//foo:bar_deploy.jar"). So it depends on the implementation of the rule for "@com_xyc//:spits2filesasoutput"

Other times rules put their outputs in providers, which are available to other rules. So depending on the implementation of the rule for "@com_xyc//:spits2filesasoutput", you might need to create a Starlark rule instead of using a genrule so that you can access the outputs in the other rule's providers.

To view this discussion on the web visit https://groups.google.com/d/msgid/bazel-discuss/74A3F6D0-D6A7-46C6-B8B2-F92E6334980D%40gmail.com.

[kv]

Thanks Alex for the explanation. Makes sense. What can I do in the upstream rule to make this easy? The goal is to just rename a file which is an output of another rule. 

On Thursday, March 19, 2020 at 3:57:21 PM UTC-7, Alex Humesky wrote:

$(location) requires a label, and only some outputs of a rule have labels (these are the "implicit outputs" of a rule, e.g. for a java_binary named "bar" in a package named "foo", there are the labels "//foo:bar" and "//foo:bar_deploy.jar"). So it depends on the implementation of the rule for "@com_xyc//:spits2filesasoutput"

Other times rules put their outputs in providers, which are available to other rules. So depending on the implementation of the rule for "@com_xyc//:spits2filesasoutput", you might need to create a Starlark rule instead of using a genrule so that you can access the outputs in the other rule's providers.

On Thu, Mar 19, 2020 at 6:47 PM Alex Garcia Mayans <the...@gmail.com> wrote:

$(location @com_xyc//:otherfn.txt) maybe ?

Regards,

Alexandre Garcia Mayans

On 19 Mar 2020, at 23:40, kv <vijay....@gmail.com> wrote:



in cmd attribute of genrule rule //:abc: label '//:otherfn.txt' in $(location) expression is not a declared prerequisite of this rule

I'm getting this error. What am I missing?

On Thursday, March 19, 2020 at 3:18:06 PM UTC-7, Alex Garcia wrote:

$(location otherfn.txt) should work

Alexandre Garcia Mayans

On 19 Mar 2020, 23:15 +0100, kv <vijay....@gmail.com>, wrote:

genrule(

     name = "abc",

     srcs =[ "@com_xyc//:spits2filesasoutput"], #<---- this rule gives me 2 files, fn.txt, otherfn.txt

     outs = ["newnamefn.log"],

     cmd = """

     mv $(locations @com_xyc//:spits2filesasoutput) $@

     """

)

I just want to rename otherfn.txt to newnamefn.log. How do I reference that specific file from the srcs?

Thanks

kv

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[Alex Humesky]

The easiest thing to do is to modify the genrule to find the file you're interested in inside "$(locations @com_xyc//:spits2filesasoutput)", e.g. like using grep. This requires that you put some information about how the file is named inside the genrule. That might be fine as a one-off, but if you need to do this a lot in a generic way, you can maybe use a macro to make it reusable.

(also, note that you'll want to use cp instead of mv, since that file might be an input to other actions)

The other options are

1. Have the other rule add the files to an output group in an OutputGroupInfo in the rule's providers, and then use a filegroup rule to give a label to that output group

See

https://docs.bazel.build/versions/master/skylark/rules.html#requesting-output-files

https://docs.bazel.build/versions/master/be/general.html#filegroup.output_group

2. Use attr.output to create an implicit output in the other rule

https://docs.bazel.build/versions/master/skylark/lib/attr.html#output

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