xtask: support MSRV

xtask/Cargo.toml

@@ -1,8 +1,11 @@
 [package]
 name = "xtask"
 version = "0.1.0"
-edition = "2021"
+edition = "2018"
 
 [dependencies]
 anyhow = "1.0.51"
-clap = { version = "3.0.0-rc.7", features = ["derive"] }
+
+# Clap 3 requires MSRV 1.54
+rustversion = "1.0"
+structopt = { version = "0.3", default-features = false }

xtask/src/main.rs

@@ -1,8 +1,8 @@
 use anyhow::{Context, Result};
-use clap::Parser;
 use std::{collections::HashMap, process::Command};
+use structopt::StructOpt;
 
-#[derive(Parser)]
+#[derive(StructOpt)]
 enum Subcommand {
     /// Runs `cargo llvm-cov` for the PyO3 codebase.
     Coverage,
@@ -20,7 +20,7 @@ impl Subcommand {
 }
 
 fn main() -> Result<()> {
-    Subcommand::parse().execute()
+    Subcommand::from_args().execute()
 }
 
 /// Runs `cargo llvm-cov` for the PyO3 codebase.
@@ -42,18 +42,14 @@ fn subcommand_coverage() -> Result<()> {
 }
 
 fn run(command: &mut Command) -> Result<()> {
-    print!("running: {}", command.get_program().to_string_lossy());
-    for arg in command.get_args() {
-        print!(" {}", arg.to_string_lossy());
-    }
-    println!();
+    println!("running: {}", format_command(command));
     command.spawn()?.wait()?;
     Ok(())
 }
 
 fn llvm_cov_command(args: &[&str]) -> Command {
     let mut command = Command::new("cargo");
-    command.args(["llvm-cov", "--package=pyo3"]).args(args);
+    command.args(&["llvm-cov", "--package=pyo3"]).args(args);
     command
 }
 
@@ -92,7 +88,32 @@ fn get_coverage_env() -> Result<HashMap<String, String>> {
 }
 
 // Replacement for str.split_once() on Rust older than 1.52
+#[rustversion::before(1.52)]
 fn split_once(s: &str, pat: char) -> Option<(&str, &str)> {
     let mut iter = s.splitn(2, pat);
     Some((iter.next()?, iter.next()?))
 }
+
+#[rustversion::since(1.52)]
+fn split_once(s: &str, pat: char) -> Option<(&str, &str)> {
+    s.split_once(pat)
+}
+
+#[rustversion::since(1.57)]
+fn format_command(command: &Command) -> String {
+    let mut buf = String::new();
+    buf.push('`');
+    buf.push_str(&command.get_program().to_string_lossy());
+    for arg in command.get_args() {
+        buf.push(' ');
+        buf.push_str(&arg.to_string_lossy());
+    }
+    buf.push('`');
+    buf
+}
+
+#[rustversion::before(1.57)]
+fn format_command(command: &Command) -> String {
+    // Debug impl isn't as nice as the above, but will do on < 1.57
+    format!("{:?}", command)
+}