Different behavior of resolution when using `let` value assignments

[manuelscurti]

Hi there!

What version of CUE are you using (cue version)?

Tried on:
v0.16.0-alpha.1
v0.15.4
v0.15.3
v0.14.1
v0.13.2 <- in this version, the following bug does not reproduce

Does this issue reproduce with the latest stable release?

Yes

What did you do?

The following input YAML

components:
  - id: urn:dmb:cmp:testdomain:system:0:component:subcomponent
id: urn:dmb:cmp:testdomain:system:0:component

run against this CUE script:

import "strings"

let splits = strings.Split(id, ":")
let domain = splits[3]
let majorVersion = splits[5]

let componentIdPattern = "^urn:dmb:cmp:\(domain):[a-zA-Z0-9_\\-]+:\(majorVersion):[a-zA-Z0-9_\\-]+$"
let subcomponentIdPattern = "^urn:dmb:cmp:\(domain):[a-zA-Z0-9_\\-]+:\(majorVersion):[a-zA-Z0-9_\\-]+:subcomponent$"

#Id:               string & =~"^[a-zA-Z0-9:._\\-]+$"
#ComponentId: #Id & =~componentIdPattern 
#SubcomponentId:  #Id & =~subcomponentIdPattern 

#Workload: {
  id:                       #SubcomponentId
  ...
}

id!:                       #ComponentId
components: [#Workload]

with the following command:

$ cue vet file.yaml validator.cue

returns:

$ cue vet file.yaml validator.cue       
                                                                                                                                                                                                                
components.0.id: invalid value "urn:dmb:cmp:testdomain:system:0:component:subcomponent" (out of bound =~"^urn:dmb:cmp::[a-zA-Z0-9_\\-]+:0:[a-zA-Z0-9_\\-]+:subcomponent$"):
    ./not-working.cue:12:25
    ./descriptor.yaml:2:9
    ./not-working.cue:15:29

While instead, if I now switch the order of the id field in the file.yaml like this:

id: urn:dmb:cmp:testdomain:system:0:component
components:
  - id: urn:dmb:cmp:testdomain:system:0:component:subcomponent

and run again the same command, I get:

$ cue vet file.yaml validator.cue
$ 

no output, meaning validation went through.

What did you expect to see?

Same behavior, independently of the order of input fields.

The expected behavior was happening in v0.13.2

What did you see instead?

Different behavior

Thank you

[mvdan]

Reduced to the following:

exec cue vet -c in.cue data-idfirst.yaml

exec cue vet -c in.cue data-idlast.yaml

-- in.cue --
import "strings"

let splits = strings.Split(id, "_never_")
let prefix = splits[0]

#ID:    =~"^\(prefix)$"
#SubID: =~"^\(prefix):sub$"

id: #ID
subid: #SubID

-- data-idfirst.yaml --
id: "foo"
subid: "foo:sub"

-- data-idlast.yaml --
subid: "foo:sub"
id: "foo"

As of 9e34d67:

> exec cue vet -c in.cue data-idfirst.yaml
> exec cue vet -c in.cue data-idlast.yaml
[stderr]
subid: invalid value "foo:sub" (out of bound =~"^:sub$"):
    ./in.cue:7:9
    ./data-idlast.yaml:1:8
    ./in.cue:10:8
[exit status 1]
FAIL: repro.txtar:3: unexpected command failure

Bisected to b96ed2c.

[mvdan]

Potential fix at https://review.gerrithub.io/c/cue-lang/cue/+/1230698.