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e5ac9a2734
The Rego VM was designed around Rego's semantics, but Azure Policy needs a few things Rego doesn't: host-supplied context alongside input/data, undefined-to-null coercion for missing fields, skip-undefined collection behavior for wildcard aliases, and non-vacuous iteration over non-array values. This commit adds five new instructions to bridge those gaps: LoadContext / LoadMetadata — give programs access to host-supplied evaluation context and cached program metadata at runtime. ArrayPushDefined — like ArrayPush but silently drops undefined values, so wildcard alias collection (field[*].property) excludes absent nested properties instead of leaking undefined entries into the array. ReturnUndefinedIfNotTrue — early return with Undefined when a guard condition isn't satisfied, without tripping a VM assertion failure. This models "condition doesn't match" cleanly. CoalesceUndefinedToNull — turns Undefined into Null in-place so that downstream builtins see null rather than short-circuiting on undefined. The loop engine also gains an Azure Policy mode: when the source language is "azure_policy", an Every loop over a non-array value (scalars, null, objects) iterates once over a virtual Null element instead of being vacuously true. This matches how field[*] behaves on non-array fields in Azure Policy — the condition body runs once against Null, which typically evaluates to false. On the plumbing side: the VM gets a context field with set_context(), metadata is cached as a Value on program load, and map_limit_error is inlined into memory_check since it had only one call site. Four new YAML test suites (~880 lines) cover the new instructions and context/metadata loading, along with instruction parser, display, and assembly listing support for everything added here.
195 lines
6.2 KiB
YAML
195 lines
6.2 KiB
YAML
# CoalesceUndefinedToNull instruction test suite
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#
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# Used by the Azure Policy compiler to convert undefined (missing) field values
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# to null before passing them to comparison operators. This prevents undefined
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# propagation from short-circuiting subsequent builtins.
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#
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# Semantics:
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# - If register == Undefined → replaces it with Null (in-place).
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# - For any other value (null, bool, number, string, array, object) → no-op.
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cases:
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# =========================================================================
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# Basic coalescing behavior
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# =========================================================================
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- note: undefined_becomes_null
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description: Undefined register value is replaced with null
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literals: []
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instructions:
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- "CoalesceUndefinedToNull { register: 0 }"
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- "Return { value: 0 }"
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want_result: null
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- note: null_unchanged
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description: Null value is not modified
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literals: []
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instructions:
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- "LoadNull { dest: 0 }"
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- "CoalesceUndefinedToNull { register: 0 }"
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- "Return { value: 0 }"
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want_result: null
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- note: true_unchanged
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description: Boolean true is not modified
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literals: []
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instructions:
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- "LoadTrue { dest: 0 }"
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- "CoalesceUndefinedToNull { register: 0 }"
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- "Return { value: 0 }"
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want_result: true
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- note: false_unchanged
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description: Boolean false is not modified
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literals: []
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instructions:
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- "LoadFalse { dest: 0 }"
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- "CoalesceUndefinedToNull { register: 0 }"
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- "Return { value: 0 }"
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want_result: false
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- note: number_unchanged
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description: Number value is not modified
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literals:
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- 42
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instructions:
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- "Load { dest: 0, literal_idx: 0 }"
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- "CoalesceUndefinedToNull { register: 0 }"
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- "Return { value: 0 }"
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want_result: 42
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- note: string_unchanged
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description: String value is not modified
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literals:
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- "hello"
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instructions:
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- "Load { dest: 0, literal_idx: 0 }"
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- "CoalesceUndefinedToNull { register: 0 }"
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- "Return { value: 0 }"
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want_result: "hello"
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- note: empty_string_unchanged
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description: Empty string is not modified (not confused with undefined)
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literals:
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- ""
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instructions:
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- "Load { dest: 0, literal_idx: 0 }"
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- "CoalesceUndefinedToNull { register: 0 }"
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- "Return { value: 0 }"
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want_result: ""
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- note: array_unchanged
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description: Array value is not modified
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literals: []
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instructions:
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- "ArrayNew { dest: 0 }"
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- "CoalesceUndefinedToNull { register: 0 }"
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- "Return { value: 0 }"
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want_result: []
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# =========================================================================
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# Multiple coalesces — only undefined registers are affected
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# =========================================================================
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- note: selective_coalescing
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description: Only undefined registers are coalesced; others remain unchanged
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literals:
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- 99
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instructions:
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- "Load { dest: 0, literal_idx: 0 }"
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- "CoalesceUndefinedToNull { register: 0 }"
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- "CoalesceUndefinedToNull { register: 1 }"
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- "ArrayNew { dest: 2 }"
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- "ArrayPush { arr: 2, value: 0 }"
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- "ArrayPush { arr: 2, value: 1 }"
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- "Return { value: 2 }"
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want_result: [99, null]
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# =========================================================================
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# Interaction with ReturnUndefinedIfNotTrue
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# =========================================================================
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- note: coalesce_then_guard_null_returns_undefined
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description: >
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Coalescing undefined to null, then passing to ReturnUndefinedIfNotTrue
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returns undefined (null is not true)
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literals:
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- "should not reach"
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instructions:
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- "CoalesceUndefinedToNull { register: 0 }"
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- "ReturnUndefinedIfNotTrue { condition: 0 }"
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- "Load { dest: 1, literal_idx: 0 }"
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- "Return { value: 1 }"
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want_result: "#undefined"
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- note: coalesce_preserves_true_for_guard
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description: >
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Coalescing a true value is a no-op, so ReturnUndefinedIfNotTrue
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continues execution
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literals:
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- "reached"
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instructions:
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- "LoadTrue { dest: 0 }"
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- "CoalesceUndefinedToNull { register: 0 }"
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- "ReturnUndefinedIfNotTrue { condition: 0 }"
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- "Load { dest: 1, literal_idx: 0 }"
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- "Return { value: 1 }"
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want_result: "reached"
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# =========================================================================
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# Interaction with HostAwait (suspendable mode)
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# =========================================================================
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- note: coalesce_after_host_await_undefined_response
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description: >
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HostAwait returns undefined, CoalesceUndefinedToNull converts it to null
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literals:
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- "await-id"
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- "arg"
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instructions:
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- "Load { dest: 1, literal_idx: 1 }"
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- "Load { dest: 2, literal_idx: 0 }"
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- "HostAwait { dest: 0, arg: 1, id: 2 }"
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- "CoalesceUndefinedToNull { register: 0 }"
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- "Return { value: 0 }"
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host_await_responses:
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- id: "await-id"
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value: "#undefined"
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want_result: null
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- note: coalesce_after_host_await_value_response
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description: >
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HostAwait returns a real value, CoalesceUndefinedToNull is a no-op
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literals:
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- "await-id"
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- "arg"
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instructions:
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- "Load { dest: 1, literal_idx: 1 }"
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- "Load { dest: 2, literal_idx: 0 }"
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- "HostAwait { dest: 0, arg: 1, id: 2 }"
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- "CoalesceUndefinedToNull { register: 0 }"
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- "Return { value: 0 }"
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host_await_responses:
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- id: "await-id"
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value: "real-value"
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want_result: "real-value"
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- note: suspendable_coalesce_after_host_await
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description: >
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In suspendable mode: HostAwait suspends and resumes with value,
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CoalesceUndefinedToNull is a no-op
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literals:
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- "await-id"
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- "arg"
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instructions:
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- "Load { dest: 1, literal_idx: 1 }"
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- "Load { dest: 2, literal_idx: 0 }"
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- "HostAwait { dest: 0, arg: 1, id: 2 }"
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- "CoalesceUndefinedToNull { register: 0 }"
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- "Return { value: 0 }"
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host_await_responses_suspendable:
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- id: "await-id"
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value: 42
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ignore_run_to_completion_hostawait_failure: true
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want_result: 42
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