fix: raise CompileError when solc returns no contracts to avoid batch crash

[tamtamchik]

Summary

• compile_contracts() returned json.loads(stdout) without checking for "contracts". When solc returned an errors-only response (e.g. unresolved import from version drift in a dependency), compile_contract_from_explorer() did compile_contracts(...)["contracts"] and raised KeyError.
• KeyError is not a BaseCustomException, so it bypassed both the per-contract and outer handlers in process_config, killing the whole batch — one bad implementation address took down all remaining contracts in the config.
• Fix: compile_contracts() now raises a structured CompileError with formatted solc error messages when output has no "contracts" key, and also when stdout is non-JSON. The existing except BaseCustomException in process_config then catches it and continues with the next contract.

Test plan

• uv run pytest -q — 92 passed
• New tests/test_compiler.py covers: errors-only output, warning-only filtering, invalid JSON, happy path
• uv run black --check diffyscan/utils/compiler.py tests/test_compiler.py

[Copilot]

Pull request overview

This PR hardens Solidity compilation error handling so that when solc --standard-json returns an errors-only (or otherwise malformed) response, the tool raises a structured CompileError instead of allowing a downstream KeyError to crash batch processing.

Changes:

• Parse solc stdout defensively in compile_contracts() and raise CompileError for non-JSON output or missing "contracts".
• Surface formatted solc error messages (filtering warnings when errors exist) in the raised exception.
• Add unit tests covering errors-only output, warning filtering, invalid JSON, and success cases.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
diffyscan/utils/compiler.py	Adds safer JSON parsing and explicit CompileError paths when solc output is malformed or missing contracts.
tests/test_compiler.py	Introduces pytest coverage for the new compile_contracts() error-handling behavior.

Comments suppressed due to low confidence (1)

diffyscan/utils/compiler.py:123

• This branch assumes output is a dict (uses output.get(...)), but if solc (or a wrapper) returns valid JSON that isn't an object (e.g., null, list, or string), this will raise AttributeError and bypass CompileError. Consider validating isinstance(output, dict) before checking keys / calling .get, and raising CompileError with a clear diagnostic when the top-level JSON shape is unexpected.

    if "contracts" not in output:
        errors = output.get("errors") or []
        fatal = [e for e in errors if e.get("severity") == "error"] or errors
        msgs = "\n".join(
            e.get("formattedMessage") or e.get("message") or str(e) for e in fatal
        )

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