[App Service] az functionapp deployment source config-zip: Fix KeyError 'FUNCTIONS_WORKER_RUNTIME' for Go on Flex Consumption

[harshivcodes]

Related command
az functionapp deployment source config-zip

(Also affects every other az functionapp command that goes through _FlexFunctionAppStackRuntimeHelper: functionapp create, functionapp config set for runtime, functionapp list-flexconsumption-runtimes, functionapp list-flexconsumption-locations, functionapp deployment github-actions add, functionapp flex-migration.)

Description

az functionapp deployment source config-zip crashes with KeyError: 'FUNCTIONS_WORKER_RUNTIME' for every Go function app on Flex Consumption, before any zip is uploaded. The crash is in _FlexFunctionAppStackRuntimeHelper._parse_raw_stacks at custom.py:7771:

runtime_name = (runtime_settings['appSettingsDictionary']['FUNCTIONS_WORKER_RUNTIME'] or
                runtime['name'])

The intent is to prefer FUNCTIONS_WORKER_RUNTIME but fall back to runtime['name'] when FWR isn't set. But the dictionary access is hard-indexed instead of using .get(), so Python raises KeyError before the or fallback can execute.

This is fine for node/python/java/powershell/dotnet — their stack definitions populate appSettingsDictionary.FUNCTIONS_WORKER_RUNTIME in the API response. It breaks for Go because Flex Consumption Go apps deliberately return appSettingsDictionary: {} (Go on Flex doesn't require FWR on the app at runtime — native binaries, no managed worker). The Go stack definition isn't introducing this bug; it's exposing a latent over-assumption in the CLI parser that was hidden only because every prior Flex language happened to populate FWR.

Fix: change the chained [ ] lookup to use .get() so the existing or runtime['name'] fallback can run. This matches the defensive pattern already used by the sibling Windows/Linux helper _FunctionAppStackRuntimeHelper._parse_minor_version in the same file.

For Go, runtime['name'] resolves to "go", the stack registers as "go", and downstream resolve("go") matches the deployed app's functionAppConfig.runtime.name == "go" cleanly. Other languages are unaffected — their FWR value is truthy, so or short-circuits before the fallback.

Testing Guide

1. Existing mock test suite still passes (25/25):

   python -m unittest azure.cli.command_modules.appservice.tests.latest.test_functionapp_commands_thru_mock
   

2. Two new regression tests added (also pass):
   • test_flex_parse_raw_stacks_handles_empty_app_settings_dictionary — feeds a Go-shaped stack with appSettingsDictionary: {} and asserts resolve('go', '1.0') returns a runtime named "go" (this test fails on the current dev branch with KeyError).
   • test_flex_parse_raw_stacks_prefers_functions_worker_runtime_when_present — feeds a dotnet-isolated stack and asserts FWR overrides runtime['name'] (preserves canonical-name semantics).
3. Verified end-to-end against a live Go Flex Consumption app using the editable install:

   az functionapp deployment source config-zip -g <rg> -n <app> --src <zip>
   # -> "Deployment was successful."
   

History Notes

[App Service] az functionapp deployment source config-zip: Fix KeyError 'FUNCTIONS_WORKER_RUNTIME' for Go function apps on Flex Consumption

[azure-client-tools-bot-prd]

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[azure-client-tools-bot-prd]

Hi @harshivcodes,
Since the current milestone time is less than 7 days, this pr will be reviewed in the next milestone.

[azure-client-tools-bot-prd]

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[yonzhan]

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[Copilot]

Pull request overview

Fixes a crash in the App Service Function App “Flex Consumption” runtime stack parser where Go stacks may return an empty appSettingsDictionary, causing a KeyError when reading FUNCTIONS_WORKER_RUNTIME. This unblocks az functionapp deployment source config-zip (and other az functionapp flows that use _FlexFunctionAppStackRuntimeHelper) for Go apps on Flex Consumption.

Changes:

• Make _FlexFunctionAppStackRuntimeHelper._parse_raw_stacks safely read FUNCTIONS_WORKER_RUNTIME via nested .get() with fallback to runtime['name'].
• Add regression tests covering (1) empty appSettingsDictionary (Go shape) and (2) preferring FUNCTIONS_WORKER_RUNTIME when present (e.g., dotnet-isolated).

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
src/azure-cli/azure/cli/command_modules/appservice/custom.py	Prevents KeyError by using .get() to read FUNCTIONS_WORKER_RUNTIME, preserving existing fallback behavior.
src/azure-cli/azure/cli/command_modules/appservice/tests/latest/test_functionapp_commands_thru_mock.py	Adds mocked regression tests for the empty-dictionary case and for the precedence of FUNCTIONS_WORKER_RUNTIME.

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