Allow param assignments to use null values

[jeskew]

Resolves #11301 and resolves #11531

This PR allows .bicepparam files to specify a value of null (or an expression that evaluates to null) for optional parameters, as the ARM engine will interpret a null value as equivalent to no value having been supplied for the parameter. Because this means that the param's default value (which may not be known until deploy time) will be used, this PR also prevents parameters with a null value from being used in expressions.

While working on the block, I noticed that parameters using az.getSecret are currently allowed to be used in other expressions in .bicepparam files, but the compiled value is incorrect (the JSON will use the object value that should appear in the .parameters.json file). The block was updated to also prohibit references to parameters whose value will be pulled at deploy time from KeyVault.

Microsoft Reviewers: codeflow:open?pullrequest=https://github.com/Azure/bicep/pull/11532&drop=dogfoodAlpha

[github-actions]

Test Results (osx-x64)

       33 files  ±0         33 suites  ±0   1h 44m 18s ⏱️ + 16m 24s
10 406 tests +5  10 370 ✔️ +5  36 💤 ±0  0 ❌ ±0 
12 623 runs  +5  12 587 ✔️ +5  36 💤 ±0  0 ❌ ±0 

Results for commit 83bbb24. ± Comparison against base commit 6c3a71d.

♻️ This comment has been updated with latest results.

[github-actions]

Test Results (linux-musl-x64)

       33 files  ±0         33 suites  ±0   36m 22s ⏱️ +40s
10 402 tests +5  10 366 ✔️ +5  36 💤 ±0  0 ❌ ±0 
12 619 runs  +5  12 583 ✔️ +5  36 💤 ±0  0 ❌ ±0 

Results for commit 83bbb24. ± Comparison against base commit 6c3a71d.

♻️ This comment has been updated with latest results.

[github-actions]

Test Results (linux-x64)

       33 files  ±0         33 suites  ±0   36m 41s ⏱️ - 2m 55s
10 402 tests +5  10 366 ✔️ +5  36 💤 ±0  0 ❌ ±0 
12 619 runs  +5  12 583 ✔️ +5  36 💤 ±0  0 ❌ ±0 

Results for commit 83bbb24. ± Comparison against base commit 6c3a71d.

♻️ This comment has been updated with latest results.

[github-actions]

Test Results (win-x64)

       33 files  ±0         33 suites  ±0   37m 56s ⏱️ + 1m 16s
10 414 tests +5  10 378 ✔️ +5  36 💤 ±0  0 ❌ ±0 
12 630 runs  +5  12 594 ✔️ +5  36 💤 ±0  0 ❌ ±0 

Results for commit 83bbb24. ± Comparison against base commit 6c3a71d.

♻️ This comment has been updated with latest results.

[shenglol]

[slavizh]

@jeskew
May be I am doing something wrong but I get error on the using statement as soon as I provide null value. To test:

example.bicep

param propertyx string

example.bicepparam

using 'example.bicep'
param propertyx = null

using statement throws error like: The following parameters are declared in the Bicep file but are missing an assignment in the params file: "propertyx".bicep(BCP258)

[jeskew]

@slavizh The BCP258 diagnostic is expected because propertyx is a required parameter. In order to be able to either omit a parameter or set its value to null in a .bicepparam file, the parameter needs to be optional. You can do this by setting a default value:

param propertyx string = 'default value'

or by declaring the parameter to be nullable (optional without a default value):

param propertyx string?

[slavizh]

@jeskew thanks a lot!

[islamzakyy]

@jeskew I have a question that might be related to this topic

I am trying to set a parameter value in bicepparam file from a variable that uses filter function, it failed with this error:

Failed to evaluate parameter "resourceName": Unhandled exception during evaluating template language function 'variables' is not handled.bicep(BCP338)

Here is the code:

using './storageaccount.bicep'

var pipeline_content = loadYamlContent('azure-pipelines.yml','parameters')
var tenant = pipeline_content[0].default
var env = pipeline_content[1].default[0].environmentName
var resourceGroupLocationActual = resourceGroup().name
var locationAbrv = filter(pipeline_content[1].default[0].regionDetails, rg => rg.resourceGroup == resourceGroupLocationActual)[0].abrv
param resourceName = 'r${env}${tenant}st${locationAbrv}02'

As If it requires from me to do exception handling on the filter function output, any other function apart from filter works good. Weird

[jeskew]

@islammohamed94 Could you open a separate issue? The problem you're running into is that the resourceGroup() function can't be used in .bicepparam files, but the appropriate error diagnostic isn't being raised.