fix: handle plain-text throttle responses in Invoke-AzSpotPlacementScore

[khang-11]

Summary

• When Invoke-AzSpotPlacementScore receives a throttled HTTP 429 response with a plain-text body (e.g. You are being throttled), the autorest-generated client crashes with Expected '{' or '['. Was String: You. because JsonNode.Parse() is called unconditionally on the response body regardless of content type.
• Wrap all FromJson(JsonNode.Parse(...)) call sites in Compute.cs with try/catch so that unparseable bodies return null instead of throwing. The existing onDefault handler already falls back to a RestException using the raw response body as the message when code/message are null, so the user now sees the actual throttle message rather than a parse exception.
• Add playback test cases for Invoke-AzSpotPlacementScore covering 429 with a Retry-After header and 429 without, asserting that no JSON parse exception is surfaced.

Test coverage

Test	What it covers
ThrottledWithRetryAfter	429 + plain-text body + Retry-After header → no parse crash
ThrottledWithoutRetryAfter	429 + plain-text body + no Retry-After header → no parse crash

Notes

• The fix is applied to all _Call methods in Compute.cs (not just SpotPlacement) since the same parse pattern is repeated for every API in the generated file and any of them could receive a plain-text throttle body.
• ISendAsync.cs retry middleware (Retry429, RetryError) is unchanged.

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[khang-11]

Fixes: #28765

[Copilot]

Pull request overview

This PR addresses a failure mode in the Compute AutoRest client where plain-text HTTP 429 throttling responses cause JsonNode.Parse() to throw, preventing Invoke-AzSpotPlacementScore from surfacing the actual throttling message to users.

Changes:

• Wrap AutoRest model deserialization (FromJson(JsonNode.Parse(...))) in generated/api/Compute.cs to avoid throwing on non-JSON response bodies.
• Add Pester playback tests for Invoke-AzSpotPlacementScore covering throttled 429 responses with and without Retry-After.
• Extend the SpotPlacementScore recording file with 429 plain-text response entries.

Reviewed changes

Copilot reviewed 2 out of 3 changed files in this pull request and generated 2 comments.

File	Description
src/Compute/Compute.Autorest/test/Invoke-AzSpotPlacementScore.Tests.ps1	Adds playback Pester tests for 429 throttling scenarios to ensure no JSON parse exception leaks.
src/Compute/Compute.Autorest/test/Invoke-AzSpotPlacementScore.Recording.json	Adds recorded 429 responses with text/plain bodies (with/without Retry-After).
generated/Compute/Compute.Autorest/generated/api/Compute.cs	Makes deserialization tolerant of non-JSON bodies by catching parse failures and returning null.

[Copilot]

The throttling tests assert on $Error[0] after Should -Throw. $Error is global state and can contain errors from previous tests, and Pester may not populate it reliably for terminating exceptions. Capture the thrown error explicitly (e.g., Should -Throw -PassThru or a try/catch that stores $_) and assert on that object instead; also consider adding -ErrorAction Stop to the cmdlet invocation so the failure is always terminating for the test.

Suggested change

	{
	Invoke-AzSpotPlacementScore -Location eastus -DesiredCount $desiredCount -DesiredLocation $desiredLocations -DesiredSize $desiredSizes
	} | Should -Throw
	$Error[0].Exception.Message | Should -Not -Match "Expected '\{' or '\['"
	$Error[0].Exception.Message | Should -Not -BeNullOrEmpty
	}
	It 'ThrottledWithoutRetryAfter' {
	# When the API returns 429 with a plain-text body and no Retry-After header,
	# the cmdlet should surface a clean error message (not a JSON parse exception).
	{
	Invoke-AzSpotPlacementScore -Location eastus -DesiredCount $desiredCount -DesiredLocation $desiredLocations -DesiredSize $desiredSizes
	} | Should -Throw
	$Error[0].Exception.Message | Should -Not -Match "Expected '\{' or '\['"
	$Error[0].Exception.Message | Should -Not -BeNullOrEmpty
	$thrownError = {
	Invoke-AzSpotPlacementScore -Location eastus -DesiredCount $desiredCount -DesiredLocation $desiredLocations -DesiredSize $desiredSizes -ErrorAction Stop
	} | Should -Throw -PassThru
	$thrownError.Exception.Message | Should -Not -Match "Expected '\{' or '\['"
	$thrownError.Exception.Message | Should -Not -BeNullOrEmpty
	}
	It 'ThrottledWithoutRetryAfter' {
	# When the API returns 429 with a plain-text body and no Retry-After header,
	# the cmdlet should surface a clean error message (not a JSON parse exception).
	$thrownError = {
	Invoke-AzSpotPlacementScore -Location eastus -DesiredCount $desiredCount -DesiredLocation $desiredLocations -DesiredSize $desiredSizes -ErrorAction Stop
	} | Should -Throw -PassThru
	$thrownError.Exception.Message | Should -Not -Match "Expected '\{' or '\['"
	$thrownError.Exception.Message | Should -Not -BeNullOrEmpty

[Copilot]

ThrottledWithRetryAfter uses a recording that includes a Retry-After header. The generated Retry429 middleware retries whenever Retry-After is present (even when it is 0), so playback will likely attempt multiple POSTs and expect additional +2, +3, … entries in the recording (or can loop until the mock runs out). Either disable 429 retries for this test run via AZURE_PS_HTTP_MAX_RETRIES_FOR_429 (and potentially AZURE_PS_HTTP_MAX_RETRIES) or extend the recording with the expected retry sequence (e.g., first response with Retry-After, then a terminal response without it).

[khang-11]

/azp run

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[VeryEarly]

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