ValueSet validation fails when a custom IG defines multiple unrestricted code systems

[dajaffe]

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Describe the bug
We have our own IG created with some resource's codes bound to our own internal code systems and value sets. I've noticed when a single value set includes specific codes across multiple systems, everything works as expected. However, when a value set allows all codes from multiple systems, the resource attribute bound to that value set is set as Required (not preferred) validation fails with a Terminology_PassThrough_TX_Message.

To Reproduce
Steps to reproduce the behavior:

1. Create an IG where a resource's code attribute has a required binding to a custom valueset with multiple code systems.
2. Attempt to validate or save a resource where that attribute's code is set as a code value from any of those code systems within the required valueset.

Sample ValueSet FSH. Note that we have aliases defined for the given systems.

ValueSet: ObservationMethod
Id: observation-method
Title: "Observation Method"
Description: "Set of observation methods accepted"

* ^url = $observation-method-vs
* ^status = #active
* ^version = "0.1"

* include codes from system $observation-method-cs
* include codes from system $snomed-cs
* include codes from system $loinc-cs

Enforcement in an Observation profile:

Profile: ObservationGeneric
Parent: http://hl7.org/fhir/us/qicore/StructureDefinition/qicore-observation
Description: "Generic profile of Observation"

...

* method MS
* method from ObservationMethod (required)
...

Expected behavior
Any codevalue from all code systems specified in the valueset pass validation.

Error response:

{
    "resourceType": "OperationOutcome",
    "issue": [
        {
            "extension": [
                {
                    "url": "http://hl7.org/fhir/StructureDefinition/operationoutcome-issue-line",
                    "valueInteger": 25
                },
                {
                    "url": "http://hl7.org/fhir/StructureDefinition/operationoutcome-issue-col",
                    "valueInteger": 10
                },
                {
                    "url": "http://hl7.org/fhir/StructureDefinition/operationoutcome-message-id",
                    "valueString": "Terminology_PassThrough_TX_Message"
                }
            ],
            "severity": "information",
            "code": "processing",
            "details": {
                "coding": [
                    {
                        "system": "http://hl7.org/fhir/java-core-messageId",
                        "code": "Terminology_PassThrough_TX_Message"
                    }
                ]
            },
            "diagnostics": "Unable to expand ValueSet because CodeSystem could not be found: http://loinc.org",
            "location": [
                "Observation.code",
                "Line[25] Col[10]"
            ]
        },
        {
            "extension": [
                {
                    "url": "http://hl7.org/fhir/StructureDefinition/operationoutcome-issue-line",
                    "valueInteger": 78
                },
                {
                    "url": "http://hl7.org/fhir/StructureDefinition/operationoutcome-issue-col",
                    "valueInteger": 10
                },
                {
                    "url": "http://hl7.org/fhir/StructureDefinition/operationoutcome-message-id",
                    "valueString": "Terminology_PassThrough_TX_Message"
                }
            ],
            "severity": "error",
            "code": "processing",
            "details": {
                "coding": [
                    {
                        "system": "http://hl7.org/fhir/java-core-messageId",
                        "code": "Terminology_PassThrough_TX_Message"
                    }
                ]
            },
            "diagnostics": "Unable to expand ValueSet because CodeSystem could not be found: http://loinc.org (error because this is a required binding)",
            "location": [
                "Observation.method",
                "Line[78] Col[10]"
            ]
        },
        {
            "extension": [
                {
                    "url": "http://hl7.org/fhir/StructureDefinition/operationoutcome-issue-line",
                    "valueInteger": 78
                },
                {
                    "url": "http://hl7.org/fhir/StructureDefinition/operationoutcome-issue-col",
                    "valueInteger": 10
                },
                {
                    "url": "http://hl7.org/fhir/StructureDefinition/operationoutcome-message-id",
                    "valueString": "Terminology_TX_NoValid_1_CC"
                }
            ],
            "severity": "error",
            "code": "processing",
            "details": {
                "coding": [
                    {
                        "system": "http://hl7.org/fhir/java-core-messageId",
                        "code": "Terminology_TX_NoValid_1_CC"
                    }
                ]
            },
            "diagnostics": "None of the codings provided are in the value set 'Observation Method' (https://fhir-ig.<redacted>.com/ValueSet/observation-method|0.1), and a coding from this value set is required) (codes = http://loinc.org#34391-3)",
            "location": [
                "Observation.method",
                "Line[78] Col[10]"
            ]
        }
    ]
}

Environment (please complete the following information):

• HAPI FHIR Version: 7.4.5
• OS: [e.g. iOS] Dockerized
• Browser [e.g. chrome, safari] N/A

Additional context
Add any other context about the problem here.