[monitor] Fix panic when dynamic variables block is empty#3846
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phillip-dd wants to merge 2 commits into
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[monitor] Fix panic when dynamic variables block is empty#3846phillip-dd wants to merge 2 commits into
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Fix panic 'interface conversion: interface {} is nil, not
map[string]interface {}' in buildMonitorStruct when a variables block is
empty.
This shows up when an HCL dynamic block resolves to an empty
'variables {}' block — for example:
dynamic "variables" {
for_each = var.monitoring_variables != null ? [var.monitoring_variables] : []
content {
dynamic "cloud_cost_query" {
for_each = var.monitoring_variables.cloud_cost_queries != null ? var.monitoring_variables.cloud_cost_queries : []
content { ... }
}
}
}
with 'monitoring_variables = { cloud_cost_queries = [] }'. The outer
variables block exists but has no inner content, and SDKv2 surfaces it
during PlanResourceChange/CustomizeDiff as a list containing a single
nil element. The unsafe type assertion 'v.(map[string]interface{})'
then panics and terraform plan crashes.
Add the same defensive nil-guards we already use for data_quality_query
/ aggregate_*_query / data_jobs_query at three places:
- the outer 'variables' list iteration
- the inner 'event_query' list iteration
- the inner 'cloud_cost_query' list iteration
Nil entries are skipped, matching the existing pattern; if every entry
is nil, no variables are set on the monitor, which is the same result
as omitting the block.
Add unit tests that drive buildMonitorStruct with a stub Resource and
reproduce the original panic without the fix:
- TestBuildMonitorStruct_NilVariableEntry
- TestBuildMonitorStruct_NilCloudCostQueryEntry
- TestBuildMonitorStruct_NilEventQueryEntry
Replace the previous unit tests with TestAccDatadogMonitor_DynamicEmptyVariables, an acceptance test that exercises the wrapper-module pattern from issue #3149: an outer 'dynamic "variables"' that always produces one block, and an inner 'dynamic "cloud_cost_query"' whose for_each resolves to an empty list. The result is a single empty 'variables {}' block — exactly the input shape that crashed buildMonitorStruct on master with panic: interface conversion: interface {} is nil, not map[string]interface {} before the nil-guard fix in 2b011918. Verified by temporarily reverting the production fix: the test reproduces the exact panic from the issue, then passes once the fix is reapplied. The recorded cassette mirrors TestAccDatadogMonitor_EmptySchedulingOptions (same monitor shape, no priority, no variables field in any request body since the empty block is filtered out).
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Summary
Fixes a panic that occurs when a
dynamic "variables"block in a Terraform configuration produces an emptyvariables {}block with no inner content. Fixes #3149Problem
When using the wrapper-module pattern with a
dynamic "variables"block that resolves to an empty block (nocloud_cost_query,event_query, ordata_quality_queryentries), the provider would crash duringterraform planwith:This occurred in the
buildMonitorStructfunction when attempting to type-assert nil values from the Terraform configuration.Solution
Added defensive checks in
buildMonitorStructto:variableslistThese changes allow empty
variables {}blocks to be gracefully handled, resulting in novariablesfield being sent to the API (same behavior as omitting the block entirely).Testing
Added
TestAccDatadogMonitor_DynamicEmptyVariablestest that verifies the provider can successfully create a monitor with an empty dynamic variables block, matching the real-world wrapper-module pattern from issue #3149.PR by Bits - View session in Datadog
Comment @DataDog to request changes