70 lines
2.2 KiB
Rust
70 lines
2.2 KiB
Rust
use std::error::Error;
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use std::io::Write;
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use std::io::stderr;
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/// Print an Error type and its cause recursively
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///
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/// The error is printed with "Error NNNN :" as prefix, where "NNNN" is a number which increases
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/// which each recursion into the errors cause. The error description is used to visualize what
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/// failed and if there is a cause "-- caused by:" is appended, and the cause is printed on the next
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/// line.
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///
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/// Example output:
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///
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/// ```ignore
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/// Error 1 : Some error -- caused by:
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/// Error 2 : Some other error -- caused by:
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/// Error 3 : Yet another Error -- caused by:
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/// ...
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///
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/// Error <NNNN> : <Error description>
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/// ```
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pub fn trace_error(e: &Error) {
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print_trace_maxdepth(count_error_causes(e), e, ::std::u64::MAX);
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write!(stderr(), "");
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}
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/// Print an Error type and its cause recursively, but only `max` levels
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///
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/// Output is the same as for `trace_error()`, though there are only `max` levels printed.
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pub fn trace_error_maxdepth(e: &Error, max: u64) {
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let n = count_error_causes(e);
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write!(stderr(), "{}/{} Levels of errors will be printed", (if max > n { n } else { max }), n);
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print_trace_maxdepth(n, e, max);
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write!(stderr(), "");
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}
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/// Print an Error type and its cause recursively with the debug!() macro
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///
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/// Output is the same as for `trace_error()`.
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pub fn trace_error_dbg(e: &Error) {
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print_trace_dbg(0, e);
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}
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/// Helper function for `trace_error()` and `trace_error_maxdepth()`.
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///
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/// Returns the cause of the last processed error in the recursion, so `None` if all errors where
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/// processed.
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fn print_trace_maxdepth(idx: u64, e: &Error, max: u64) -> Option<&Error> {
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if e.cause().is_some() && idx > 0 {
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print_trace_maxdepth(idx - 1, e.cause().unwrap(), max);
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write!(stderr(), " -- caused:");
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}
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write!(stderr(), "Error {:>4} : {}", idx, e.description());
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e.cause()
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}
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/// Count errors in Error::cause() recursively
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fn count_error_causes(e: &Error) -> u64 {
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1 + if e.cause().is_some() { count_error_causes(e.cause().unwrap()) } else { 0 }
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}
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fn print_trace_dbg(idx: u64, e: &Error) {
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debug!("Error {:>4} : {}", idx, e.description());
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if e.cause().is_some() {
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debug!(" -- caused by:");
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print_trace_dbg(idx + 1, e.cause().unwrap());
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}
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}
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