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BenWiederhake opened this issue Apr 12, 2025 · 1 comment
Open

Typo in #[arg()] leads to opaque error message #129

BenWiederhake opened this issue Apr 12, 2025 · 1 comment

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@BenWiederhake
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Some (somewhat reasonable?) mistakes lead to completely incomprehensible and unhelpful compiler errors. For example, writing

    #[arg("--time[X]")] // WRONG!
    IgnoreOptionArg(#[allow(dead_code)] Option<OsString>),

instead of:

    #[arg("--time[=X]")] // CORRECT!
    IgnoreOptionArg(#[allow(dead_code)] Option<OsString>),

leads to this unhelpful error message:

error: proc-macro derive panicked
  --> src/uu/du/src/du.rs:79:10
   |
79 | #[derive(Arguments)]
   |          ^^^^^^^^^
   |
   = help: message: called `Option::unwrap()` on a `None` value

How should we approach this? I suggest replacing every .unwrap within derive to a .expect. This way, we at least get some information on what's wrong. This affects the following places:

$ git grep -Pirn 'unwrap\(' derive/
derive/src/argument.rs:35:            return ArgumentsAttr::parse(attr).unwrap();
derive/src/argument.rs:43:    let attributes = get_arg_attributes(&v.attrs).unwrap();
derive/src/flags.rs:64:                    .unwrap();
derive/src/flags.rs:86:            let f = chars.next().unwrap();
derive/src/help.rs:88:        ).unwrap();
derive/src/help.rs:90:        writeln!(w, "{}", #summary).unwrap();
derive/src/help.rs:92:        writeln!(w, "\nUsage:\n  {}", format!(#usage, bin_name)).unwrap();
derive/src/help.rs:96:        writeln!(w, "{}", #after_options).unwrap();
derive/src/help.rs:103:    let manifest_dir = std::env::var("CARGO_MANIFEST_DIR").unwrap();
derive/src/help.rs:107:    let mut f = std::fs::File::open(location).unwrap();
derive/src/help.rs:108:    f.read_to_string(&mut contents).unwrap();
derive/src/help_parser.rs:117:            parse_section("some section", input).unwrap(),
derive/src/help_parser.rs:121:            parse_section("SOME SECTION", input).unwrap(),
derive/src/help_parser.rs:125:            parse_section("another section", input).unwrap(),
derive/src/help_parser.rs:146:            parse_section("after section", input).unwrap(),
derive/src/lib.rs:76:            let mut values = parser.raw_args().unwrap().collect::<Vec<OsString>>();
derive/src/lib.rs:155:            let ValueAttr { keys, value } = ValueAttr::parse(&attr).unwrap();

However, I'm not sure whether this would result in actually-useful error messages.
@BenWiederhake BenWiederhake mentioned this issue Apr 12, 2025
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@tertsdiepraam
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Good idea! I don't have time this weekend so feel free to take this up, otherwise I'll try to do this next weekend.

@BenWiederhake BenWiederhake mentioned this issue Apr 13, 2025
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@BenWiederhake @tertsdiepraam