flagon-io/hello

cat README.md && grep -n "times\|empty\|name" src/main.rs | head -40

# hello

Greets people from the command line.

## Usage

| Argument | Description |
| -------- | ----------- |
| `NAME`   | Optional. The name to greet. Only the first argument is read. Defaults to the `USER` environment variable, then to `world`. |
| `--shout` | Upper-cases the greeting. |
| `--version` | Prints the crate version and exits. |
| `--times N` | Prints the greeting `N` times. Defaults to 1. |

```sh
$ cargo run -- Ada
Hello, Ada!
```

```sh
$ cargo run -- --shout Ada
HELLO, ADA!
```

```sh
$ cargo run -- --times 2 Ada
Hello, Ada!
Hello, Ada!
```

```sh
$ cargo run -- --version
0.1.0
```

With no name it greets whoever is signed in.

## Develop

This project uses the Rust 2021 edition.

```sh
cargo test
```

## License

This project is licensed under the MIT License.
The full license text is available at https://opensource.org/license/mit.
17:    // The name given, or whoever is signed in.
18:    let name = options
19:        .name
22:    let message = greeting(&name);
24:    for _ in 0..options.times {

cat src/main.rs; grep -n "times\|empty\|trim" -B2 -A8 src/lib.rs | head -80

use std::{env, process};

use hello::{greeting, parse_args, shout};

fn main() {
    let options = match parse_args(env::args().skip(1)) {
        Ok(options) => options,
        Err(message) => {
            eprintln!("error: {message}");
            process::exit(2);
        }
    };
    if options.version {
        println!("{}", env!("CARGO_PKG_VERSION"));
        return;
    }
    // The name given, or whoever is signed in.
    let name = options
        .name
        .or_else(|| env::var("USER").ok())
        .unwrap_or_else(|| "world".to_owned());
    let message = greeting(&name);
    let line = if options.shout { shout(&message) } else { message };
    for _ in 0..options.times {
        println!("{line}");
    }
}
10-    /// Whether to print the crate version and exit (`--version`).
11-    pub version: bool,
12:    /// How many times to print the greeting (`--times N`).
13:    pub times: usize,
14-}
15-
16-impl Default for Options {
17-    fn default() -> Self {
18-        Options {
19-            name: None,
20-            shout: false,
21-            version: false,
22:            times: 1,
23-        }
24-    }
25-}
26-
27-/// Parses command-line arguments (excluding the program name).
28-///
29-/// `--shout` sets [`Options::shout`], `--version` sets
30:/// [`Options::version`], and `--times N` sets [`Options::times`] (the
31-/// next argument is consumed as the value); other arguments starting
32-/// with `--` are treated as flags and skipped. The name is the first
33-/// remaining argument.
34-///
35:/// Returns an error message if `--times` has a missing or non-numeric value.
36-pub fn parse_args<I: IntoIterator<Item = String>>(args: I) -> Result<Options, String> {
37-    let mut options = Options::default();
38-    let mut args = args.into_iter();
39-    while let Some(arg) = args.next() {
40-        if arg == "--shout" {
41-            options.shout = true;
42-        } else if arg == "--version" {
43-            options.version = true;
44:        } else if arg == "--times" {
45-            let value = args
46-                .next()
47:                .ok_or_else(|| "--times requires a value".to_owned())?;
48:            options.times = value
49-                .parse()
50:                .map_err(|_| format!("--times value must be a number, got {value:?}"))?;
51-        } else if !arg.starts_with("--") && options.name.is_none() {
52-            options.name = Some(arg);
53-        }
54-    }
55-    Ok(options)
56-}
57-
58-/// `text` upper-cased.
--
63-/// The greeting for `name`.
64-pub fn greeting(name: &str) -> String {
65:    let trimmed = name.trim();
66:    let display_name = if trimmed.is_empty() { "world" } else { trimmed };
67-    format!("Hello, {display_name}!")
68-}
69-
70-/// The farewell for `name`.
71-pub fn farewell(name: &str) -> String {
72:    let trimmed = name.trim();
73:    let display_name = if trimmed.is_empty() { "world" } else { trimmed };
74-    format!("Goodbye, {display_name}!")
75-}
76-
77-#[cfg(test)]
78-mod tests {
79-    use super::*;
80-
81-    fn args(list: &[&str]) -> Vec<String> {
--
140-
141-    #[test]
142:    fn parse_args_times_defaults_to_one() {
143:        assert_eq!(parse_args(args(&["Ada"])).unwrap().times, 1);
144-    }
145-
146-    #[test]
147:    fn parse_args_times_valid() {
148:        let options = parse_args(args(&["--times", "3", "Ada"])).unwrap();
149:        assert_eq!(options.times, 3);

python3 - <<'E'
s=open('README.md').read()
new='''## Troubleshooting

**`error: --times value must be a number, got "abc"`**

`--times` needs a whole number of zero or more. If the value is anything else, such as `abc`, `-1` or `2.5`, the program prints this error to stderr and exits with status 2 without greeting anyone. Pass a plain number, for example `--times 3`. A `--times` with no value after it also fails, with `--times requires a value`.

**The greeting says `Hello, world!` when I gave a name**

An empty or whitespace-only name, such as `cargo run -- ""`, is treated as no name and the greeting uses `world`. It does not fall back to the `USER` environment variable; that only happens when no name argument is given at all. Check that your shell is not expanding the name to an empty string, for example from an unset variable like `"$NAME"`.

## License
'''
assert s.count('## License\n')==1
open('README.md','w').write(s.replace('## License\n',new))
E
git commit -qam "Add Troubleshooting section to README" && git log --oneline | head -1

13ffb58 Add Troubleshooting section to README