Pretty print error messages in testing framework

[devin-ai-integration]

Closes #3403

Description

This PR improves error message readability in the Cadence testing framework by pretty-printing error messages with actual newlines and tabs instead of escaped sequences.

Problem

When tests fail with error messages containing newlines (\n) or tabs (\t), the testing framework was displaying them as escaped sequences, making the output hard to read:

error: I.Test.Test.Error(message: \"error: line 1\\nerror: line 2\\n\\ttab indented line\")

Solution

Added a formatValueForTestOutput helper function that:

1. Detects Test.Error values and extracts the raw message string without escaping
2. Recursively formats ScriptResult and TransactionResult to apply pretty-printing to nested errors
3. Unwraps optional values (SomeValue) since error fields are optional types

Now errors display with actual formatting:

error: I.Test.Test.Error(message: error: line 1
error: line 2
	tab indented line)

Key Changes

• stdlib/test_contract.go: Added formatValueForTestOutput and formatValueForTestOutputHelper functions
• Modified newTestTypeExpectFunction to use the new formatter
• stdlib/test_test.go: Added test case to verify newlines and tabs are not escaped

Review Focus

• Type identification: Uses strings.HasSuffix(typeID, ".Test.Error") to identify Error types - verify this is robust
• Optional unwrapping: The SomeValue unwrapping is critical since error fields are optional - this was the key bug
• Recursive formatting: Only handles ScriptResult/TransactionResult/Error specially - confirm this covers the necessary cases
• Test coverage: Single test case covers the main scenario, existing tests verify no regressions

---

Link to Devin run: https://app.devin.ai/sessions/d951b3c6a2f94efa97ac0a2f088b1f11
Requested by: [email protected]

• Targeted PR against master branch
• Linked to Github issue with discussion and accepted design OR link to spec that describes this work
• Code follows the standards mentioned here
• Updated relevant documentation
• Re-reviewed Files changed in the Github PR explorer
• Added appropriate labels

[devin-ai-integration]

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[github-actions]

Benchstat comparison

• Base branch: onflow:master
• Base commit: 3ec0c24

Results

	old.txt	new.txt
	time/op		delta
pkg:github.com/onflow/cadence/runtime goos:linux goarch:amd64
ContractFunctionInvocation-4	383µs ± 0%	404µs ± 0%	~	(p=1.000 n=1+1)
ExportType/composite_type-4	302ns ± 0%	264ns ± 0%	~	(p=1.000 n=1+1)
ExportType/simple_type-4	78.0ns ± 0%	78.0ns ± 0%	~	(p=1.000 n=1+1)
pkg:github.com/onflow/cadence/interpreter goos:linux goarch:amd64
ImperativeFib-4	21.3µs ± 0%	20.0µs ± 0%	~	(p=1.000 n=1+1)
InterpretRecursionFib-4	2.05ms ± 0%	2.06ms ± 0%	~	(p=1.000 n=1+1)
NewInterpreter/new_interpreter-4	1.03µs ± 0%	1.03µs ± 0%	~	(p=1.000 n=1+1)
NewInterpreter/new_sub-interpreter-4	322ns ± 0%	348ns ± 0%	~	(p=1.000 n=1+1)
pkg:github.com/onflow/cadence/runtime goos:linux goarch:amd64
RuntimeFungibleTokenTransferInterpreter-4	567µs ± 0%	592µs ± 0%	~	(p=1.000 n=1+1)
RuntimeFungibleTokenTransferVM-4	636µs ± 0%	625µs ± 0%	~	(p=1.000 n=1+1)
RuntimeResourceDictionaryValues-4	2.62ms ± 0%	2.62ms ± 0%	~	(p=1.000 n=1+1)
RuntimeResourceTracking-4	12.0ms ± 0%	11.8ms ± 0%	~	(p=1.000 n=1+1)
RuntimeScriptNoop-4	15.5µs ± 0%	14.9µs ± 0%	~	(p=1.000 n=1+1)
RuntimeVMInvokeContractImperativeFib-4	28.3µs ± 0%	28.4µs ± 0%	~	(p=1.000 n=1+1)
pkg:github.com/onflow/cadence/interpreter goos:linux goarch:amd64
ValueIsSubtypeOfSemaType-4	66.8ns ± 0%	66.9ns ± 0%	~	(p=1.000 n=1+1)
	alloc/op		delta
pkg:github.com/onflow/cadence/runtime goos:linux goarch:amd64
ContractFunctionInvocation-4	152kB ± 0%	152kB ± 0%	~	(p=1.000 n=1+1)
ExportType/composite_type-4	120B ± 0%	120B ± 0%	~	(all equal)
ExportType/simple_type-4	0.00B	0.00B	~	(all equal)
pkg:github.com/onflow/cadence/interpreter goos:linux goarch:amd64
ImperativeFib-4	8.30kB ± 0%	8.30kB ± 0%	~	(all equal)
InterpretRecursionFib-4	1.19MB ± 0%	1.19MB ± 0%	~	(all equal)
NewInterpreter/new_interpreter-4	976B ± 0%	976B ± 0%	~	(all equal)
NewInterpreter/new_sub-interpreter-4	232B ± 0%	232B ± 0%	~	(all equal)
pkg:github.com/onflow/cadence/runtime goos:linux goarch:amd64
RuntimeFungibleTokenTransferInterpreter-4	155kB ± 0%	156kB ± 0%	~	(p=1.000 n=1+1)
RuntimeFungibleTokenTransferVM-4	174kB ± 0%	173kB ± 0%	~	(p=1.000 n=1+1)
RuntimeResourceDictionaryValues-4	1.76MB ± 0%	1.76MB ± 0%	~	(p=1.000 n=1+1)
RuntimeResourceTracking-4	9.26MB ± 0%	9.25MB ± 0%	~	(p=1.000 n=1+1)
RuntimeScriptNoop-4	7.99kB ± 0%	7.99kB ± 0%	~	(p=1.000 n=1+1)
RuntimeVMInvokeContractImperativeFib-4	10.3kB ± 0%	10.3kB ± 0%	~	(all equal)
pkg:github.com/onflow/cadence/interpreter goos:linux goarch:amd64
ValueIsSubtypeOfSemaType-4	48.0B ± 0%	48.0B ± 0%	~	(all equal)
	allocs/op		delta
pkg:github.com/onflow/cadence/runtime goos:linux goarch:amd64
ContractFunctionInvocation-4	2.47k ± 0%	2.47k ± 0%	~	(all equal)
ExportType/composite_type-4	3.00 ± 0%	3.00 ± 0%	~	(all equal)
ExportType/simple_type-4	0.00	0.00	~	(all equal)
pkg:github.com/onflow/cadence/interpreter goos:linux goarch:amd64
ImperativeFib-4	176 ± 0%	176 ± 0%	~	(all equal)
InterpretRecursionFib-4	17.7k ± 0%	17.7k ± 0%	~	(all equal)
NewInterpreter/new_interpreter-4	15.0 ± 0%	15.0 ± 0%	~	(all equal)
NewInterpreter/new_sub-interpreter-4	4.00 ± 0%	4.00 ± 0%	~	(all equal)
pkg:github.com/onflow/cadence/runtime goos:linux goarch:amd64
RuntimeFungibleTokenTransferInterpreter-4	2.93k ± 0%	2.93k ± 0%	~	(all equal)
RuntimeFungibleTokenTransferVM-4	3.06k ± 0%	3.06k ± 0%	~	(all equal)
RuntimeResourceDictionaryValues-4	36.7k ± 0%	36.7k ± 0%	~	(all equal)
RuntimeResourceTracking-4	159k ± 0%	159k ± 0%	~	(p=1.000 n=1+1)
RuntimeScriptNoop-4	113 ± 0%	113 ± 0%	~	(all equal)
RuntimeVMInvokeContractImperativeFib-4	213 ± 0%	213 ± 0%	~	(all equal)
pkg:github.com/onflow/cadence/interpreter goos:linux goarch:amd64
ValueIsSubtypeOfSemaType-4	1.00 ± 0%	1.00 ± 0%	~	(all equal)

[turbolent]

(aside) I'm not sure the solution is what we're looking for, will pick this up later when we have time