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tamer: parse::trace: Generalize reason for trace output 

The trace outputs a note in the footer indicating _why_ it's being output,
so that the reader understands both where the potentially-unexpected
behavior originates from and so they know (in the case of the feature flag)
how to inhibit it.

That information originally lived in `Parser`, where the `cfg` directive to
enable it lives, but it was moved into the abstraction.  This corrects that.

DEV-7145
main
Mike Gerwitz 2022-07-26 13:13:31 -04:00
parent 864f50c025
commit b38c16fd08
2 changed files with 7 additions and 12 deletions
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6
tamer/src/parse/parser.rs
View File

@ -129,8 +129,10 @@ pub struct Parser<S: ParseState, I: TokenStream<S::Token>> {
/// elide the move of [`Parser::state`] in [`Parser::feed_tok`].
ctx: S::Context,
#[cfg(any(test, feature = "parser-trace-stderr"))]
tracer: trace::HumanReadableTrace,
#[cfg(test)]
tracer: trace::HumanReadableTrace<"`cfg(test)`">,
#[cfg(all(not(test), feature = "parser-trace-stderr"))]
tracer: trace::HumanReadableTrace<"`cfg(parser-trace-stderr)`">,
#[cfg(not(any(test, feature = "parser-trace-stderr")))]
tracer: trace::VoidTrace,
}

13
tamer/src/parse/trace.rs
View File

@ -98,9 +98,9 @@ impl ParserTrace for VoidTrace {
///
/// See [module-level](super) documentation for more information.
#[derive(Debug, PartialEq, Default)]
pub struct HumanReadableTrace;
pub struct HumanReadableTrace<const REASON: &'static str>;
impl ParserTrace for HumanReadableTrace {
impl<const REASON: &'static str> ParserTrace for HumanReadableTrace<REASON> {
fn trace_tok_begin<S: ParseState>(&mut self, st_orig: &S, tok: &S::Token) {
eprint!(
"\
@ -149,16 +149,9 @@ impl ParserTrace for HumanReadableTrace {
);
}
#[allow(unused_variables)]
let cfg = ""; // so that this compiles without matching cfg
#[cfg(feature = "parser-trace-stderr")]
#[allow(unused_variables)]
let cfg = "feature = \"parser-trace-stderr\"";
#[cfg(test)] // takes precedence if both are set
let cfg = "test";
eprint!(
"= note: this trace was output as a debugging aid \
because `cfg({cfg})`.\n\n",
because {REASON}.\n\n",
);
}
}