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Greets people from the command line. The sample repository for g1t.

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Extract command-line parsing into a testable function in lib.rs #24

g1t · merged · 13 entries · 4 tool calls

What happened

  1. Running on Claude Sonnet 5.5.
  2. Prompt
    You are a coding agent working in the git repository checked out in the current directory.

Issue #19: Extract command-line parsing into a testable function in lib.rs

Currently `src/main.rs` reads the name straight from `env::args().nth(1)`. Add to `src/lib.rs` a `pub struct Options { pub name: Option<String> }` and `pub fn parse_args<I: IntoIterator<Item = String>>(args: I) -> Options` (args excludes the program name). Flag-like arguments (starting with `--`) must be skipped when choosing the name, so the name is the first non-flag argument; later issues will add flags to this struct. Update `main` to use it, keeping the existing fallbacks (USER env var, then `world`) and behaviour unchanged. Add unit tests in `src/lib.rs` for: no args, a name, and a leading unknown `--flag` followed by a name.

These commands must pass when you are done. Run them if the tools are installed:
- cargo build
- cargo test

Make the change and keep it focused on the issue. Commit your work with a clear message. Do not push; that is done for you. Finish with a short summary of what you changed and why. It becomes the description of your pull request, so write it for a reviewer: plain sentences, no headings, no emoji, no checklists, and nothing about whether anything was committed or pushed. Say what you did not verify.
  3. Bashcat src/main.rs; cat src/lib.rs
  4. bash{"command":"python3 - <<'E'\np='src/lib.rs'\ns=open(p).read()\ns=s.replace('''/// The greeting for''','''/// Parsed command-line options.\n#[derive(Debug, Default, PartialEq, Eq)]\npub struct Options {\n /// The name to greet, if one was given.\n pub name: Option<String>,\n}\n\n/// Parses command-line arguments (excluding the program name).\n///\n/// Arguments starting with `--` are treated as flags and skipped; the name is\n/// the first remaining argument.\npub fn parse_args<I: IntoIterator<Item = String>>(args: I) -> Options {\n let name = args.into_iter().find(|arg| !arg.starts_with(\"--\"));\n Options { name }\n}\n\n/// The greeting for''',1)\ns=s.replace(''' use super::*;\n''',''' use super::*;\n\n fn args(list: &[&str]) -> Vec<String> {\n list.iter().map(|s| s.to_string()).collect()\n }\n\n #[test]\n fn parse_args_no_args() {\n assert_eq!(parse_args(args(&[])).name, None);\n }\n\n #[test]\n fn parse_args_name() {\n assert_eq!(parse_args(args(&[\"Ada\"])).name.as_deref(), Some(\"Ada\"));\n }\n\n #[test]\n fn parse_args_skips_leading_flag() {\n assert_eq!(\n parse_args(args(&[\"--unknown\", \"Ada\"])).name.as_deref(),\n Some(\"Ada\")\n );\n }\n''',1)\nopen(p,'w').write(s)\np='src/main.rs'\ns=open(p).read()\ns=s.replace('use hello::greeting;','use hello::{greeting, parse_args};')\ns=s.replace('''env::args()\n .nth(1)\n''','''parse_args(env::args().skip(1))\n .name\n''')\nopen(p,'w').write(s)\nE\ncargo build 2>&1|tail -3; cargo test 2>&1|grep -E \"test result|FAIL|error\""}
  5. Bashpython3 - <<'E' p='src/lib.rs' s=open(p).read() s=s.replace('''/// The greeting for''','''/// Parsed command-line options. #[derive(Debug, Default, PartialEq, Eq)] pub struct Options { /// The name to greet, if one was given. pub name: Option<String>, } /// Parses command-line arguments (excluding the program name). /// /// Arguments starting with `--` are treated as flags and skipped; the name is /// the first remaining argument. pub fn parse_args<I: IntoIterator<Item = String>>(args: I) -> Options { let name = args.into_iter().find(|arg| !arg.starts_with("--")); Options { name } } /// The greeting for''',1) s=s.replace(''' use super::*; ''',''' use super::*; fn args(list: &[&str]) -> Vec<String> { list.iter().map(|s| s.to_string()).collect() } #[test] fn parse_args_no_args() { assert_eq!(parse_args(args(&[])).name, None); } #[test] fn parse_args_name() { assert_eq!(parse_args(args(&["Ada"])).name.as_deref(), Some("Ada")); } #[test] fn parse_args_skips_leading_flag() { assert_eq!( parse_args(args(&["--unknown", "Ada"])).name.as_deref(), Some("Ada") ); } ''',1) open(p,'w').write(s) p='src/main.rs' s=open(p).read() s=s.replace('use hello::greeting;','use hello::{greeting, parse_args};') s=s.replace('''env::args() .nth(1) ''','''parse_args(env::args().skip(1)) .name ''') open(p,'w').write(s) E cargo build 2>&1|tail -3; cargo test 2>&1|grep -E "test result|FAIL|error"
  6. Bashgit commit -qam "Extract argument parsing into parse_args in lib.rs" && git log --oneline | head -1

  7. I moved argument parsing out of `main` into `src/lib.rs`. It adds `Options { name: Option<String> }` and `parse_args`, which takes the arguments without the program name. Arguments starting with `--` are skipped, and the name is the first argument left over. `main` now calls `parse_args(env::args().skip(1))` and falls back to the `USER` env var and then `world`, as before. One small change in behaviour: a leading `--flag` is no longer taken as the name. Previously it would have been. I added three unit tests for no args, a plain name, and a leading `--unknown` flag followed by a name. `cargo build` and `cargo test` both pass. I didn't run the binary by hand.

  8. This run cost $0.0670 over 5 turns.
  9. Pushed 76b37094ade6.