cargo-log-parser

Cargo Log Parser

Parse cargo build logs to extract and filter errors/warnings with precise log boundaries.

Quick Start

# From file
python scripts/cargo_log_parser.py build.log --errors

# From stdin (pipe from cargo)
cargo build 2>&1 | python scripts/cargo_log_parser.py --errors

Key Filters

Flag	Purpose	Example
-e, --errors	Errors only	--errors
-w, --warnings	Warnings only	--warnings
-f, --file PATTERN	Filter by file path regex	--file "tests/.*"
-m, --message PATTERN	Filter by message regex	--message "cannot find"
-c, --code PATTERN	Filter by error code	--code "E0425"

Output Modes

Flag	Output Style
(default)	Detailed LLM-friendly format with context
--stream	Compact one-line-per-diagnostic
--raw	Original log text for matches only
--json	Structured JSON output
-v, --verbose	Include raw log text in output

Common Patterns

# Errors in test files only
python scripts/cargo_log_parser.py build.log --errors --file "tests/.*"

# Find "not found" errors
python scripts/cargo_log_parser.py build.log --errors --message "cannot find|not found"

# All E04xx errors (name resolution)
python scripts/cargo_log_parser.py build.log --code "E04\d\d"

# Group errors by file
python scripts/cargo_log_parser.py build.log --errors --group-by-file

# Group by error code
python scripts/cargo_log_parser.py build.log --errors --group-by-code

# Quick summary
python scripts/cargo_log_parser.py build.log --summary

Python API

from cargo_log_parser import CargoLogParser, LogQuery, DiagnosticLevel

parser = CargoLogParser()
parsed = parser.parse_file("build.log")
query = LogQuery(parsed)

# Filter errors
errors = query.find_errors(file_pattern=r"tests/.*", message_pattern=r"cannot find")

# Get exact log boundaries
for error in errors:
    bounds = query.get_error_boundaries(error)
    print(f"Lines {bounds['line_start']}-{bounds['line_end']}")
    print(bounds['raw_text'])

# Group and analyze
by_file = query.group_by_file(level=DiagnosticLevel.ERROR)
by_code = query.group_by_code()

Regex Reference

Pattern	Matches
tests/.*	Test files
src/.*	Source files
.*/mod\.rs	Any mod.rs
E03\d\d	Borrow checker errors
E04\d\d	Name resolution errors
unused_.*	Unused warnings