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How to Handle Errors

This guide shows you how to handle failures in BXL script when running bxl operations, like analysis, queries, build artifact and other operations. You can find all available operations at here. You'll learn how to recover from errors and running these operations in parallel.

Running Single Operations with Error Recovery​

To run a single operation with error handling:

1. Create a lazy operation using the appropriate​

ctx.lazy method:

lazy_analysis = ctx.lazy.analysis(node)

It will return a Lazy object.

2. Add error handling and resolve the operation:​

result = lazy_analysis.catch().resolve()

The result will be of type Result[bxl.AnalysisResult], allowing you to check for and handle errors.

if result.is_ok():
    analysis_res = result.unwrap()
else:
    error = result.unwrap_err()

If resolving Lazy object without calling catch(), it will return bxl.AnalysisResult and the bxl script will fail if this operation fails.

Handling Multiple Operations in Parallel​

To run multiple operations while handling potential failures:

1. Create your lazy operations:​

lazy_ops = [
    ctx.lazy.analysis(node1),
    ctx.lazy.analysis(node2),
    ctx.lazy.configured_target_node(target1)
]

2. Choose your error handling approach:​

For collective error handling (stop on first error):​

result = ctx.lazy.join(lazy_ops).catch().resolve()

The Return type is Result[list[bxl.AnalysisResult]]

For individual error handling per operation:​

result = ctx.lazy.join([op.catch() for op in lazy_ops]).resolve()

The Return type is list[Result[bxl.AnalysisResult]]

Examples​

Examples can be found at tests/core/bxl/test_lazy_build_artifact_data/lazy_build_artifact.bxl of buck2 repo folder.

Run such command at tests/core/bxl/test_lazy_build_artifact_data to run the example bxl script

buck2 bxl lazy_build_artifact.bxl:build_artifact