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Rewrite show_md_content_with_pager.

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I think the control flow in this function is complicated and confusing,
largely due to the use of two booleans `print_formatted` and
`fallback_to_println` that are set in multiple places and then used to
guide proceedings.

As well as hurting readability, this leads to at least one bug: if the
`write_termcolor_buf` call fails and the pager also fails, the function
will try to print color output to stdout, but that output will be empty
because `write_termcolor_buf` failed. I.e. the `if fallback_to_println`
body fails to check `print_formatted`.

This commit rewrites the function to be neater and more Rust-y, e.g. by
putting the result of `write_termcolor_buf` into an `Option` so it can
only be used on success, and by using `?` more. It also changes
terminology a little, using "pretty" to mean "formatted and colorized".
The result is a little shorter, more readable, and less buggy.
This commit is contained in:
Nicholas Nethercote 2024-11-20 14:15:59 +11:00
parent 91164957ec
commit 525e1919f7
1 changed files with 44 additions and 50 deletions
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94
compiler/rustc_driver_impl/src/lib.rs
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@ -15,6 +15,7 @@
#![feature(panic_update_hook)] #![feature(panic_update_hook)]
#![feature(result_flattening)] #![feature(result_flattening)]
#![feature(rustdoc_internals)] #![feature(rustdoc_internals)]
#![feature(try_blocks)]
#![warn(unreachable_pub)] #![warn(unreachable_pub)]
// tidy-alphabetical-end // tidy-alphabetical-end
@ -564,70 +565,63 @@ fn handle_explain(early_dcx: &EarlyDiagCtxt, registry: Registry, code: &str, col
} }
} }
/// If color is always or auto, print formatted & colorized markdown. If color is never or /// If `color` is `always` or `auto`, try to print pretty (formatted & colorized) markdown. If
/// if formatted printing fails, print the raw text. /// that fails or `color` is `never`, print the raw markdown.
/// ///
/// Prefers a pager, falls back standard print /// Uses a pager if possible, falls back to stdout.
fn show_md_content_with_pager(content: &str, color: ColorConfig) { fn show_md_content_with_pager(content: &str, color: ColorConfig) {
let mut fallback_to_println = false;
let pager_name = env::var_os("PAGER").unwrap_or_else(|| { let pager_name = env::var_os("PAGER").unwrap_or_else(|| {
if cfg!(windows) { OsString::from("more.com") } else { OsString::from("less") } if cfg!(windows) { OsString::from("more.com") } else { OsString::from("less") }
}); });
let mut cmd = Command::new(&pager_name); let mut cmd = Command::new(&pager_name);
// FIXME: find if other pagers accept color options if pager_name == "less" {
let mut print_formatted = if pager_name == "less" { cmd.arg("-R"); // allows color escape sequences
cmd.arg("-R"); }
true
} else { let pretty_on_pager = match color {
["bat", "batcat", "delta"].iter().any(|v| *v == pager_name) ColorConfig::Auto => {
// Add other pagers that accept color escape sequences here.
["less", "bat", "batcat", "delta"].iter().any(|v| *v == pager_name)
}
ColorConfig::Always => true,
ColorConfig::Never => false,
}; };
if color == ColorConfig::Never { // Try to prettify the raw markdown text. The result can be used by the pager or on stdout.
print_formatted = false; let pretty_data = {
} else if color == ColorConfig::Always { let mdstream = markdown::MdStream::parse_str(content);
print_formatted = true; let bufwtr = markdown::create_stdout_bufwtr();
} let mut mdbuf = bufwtr.buffer();
if mdstream.write_termcolor_buf(&mut mdbuf).is_ok() { Some((bufwtr, mdbuf)) } else { None }
};
let mdstream = markdown::MdStream::parse_str(content); // Try to print via the pager, pretty output if possible.
let bufwtr = markdown::create_stdout_bufwtr(); let pager_res: Option<()> = try {
let mut mdbuf = bufwtr.buffer(); let mut pager = cmd.stdin(Stdio::piped()).spawn().ok()?;
if mdstream.write_termcolor_buf(&mut mdbuf).is_err() {
print_formatted = false;
}
if let Ok(mut pager) = cmd.stdin(Stdio::piped()).spawn() { let pager_stdin = pager.stdin.as_mut()?;
if let Some(pipe) = pager.stdin.as_mut() { if pretty_on_pager && let Some((_, mdbuf)) = &pretty_data {
let res = if print_formatted { pager_stdin.write_all(mdbuf.as_slice()).ok()?;
pipe.write_all(mdbuf.as_slice()) } else {
} else { pager_stdin.write_all(content.as_bytes()).ok()?;
pipe.write_all(content.as_bytes())
};
if res.is_err() {
fallback_to_println = true;
}
}
if pager.wait().is_err() {
fallback_to_println = true;
}
} else {
fallback_to_println = true;
}
// If pager fails for whatever reason, we should still print the content
// to standard output
if fallback_to_println {
let fmt_success = match color {
ColorConfig::Auto | ColorConfig::Always => bufwtr.print(&mdbuf).is_ok(),
ColorConfig::Never => false,
}; };
if !fmt_success { pager.wait().ok()?;
safe_print!("{content}"); };
} if pager_res.is_some() {
return;
} }
// The pager failed. Try to print pretty output to stdout.
if let Some((bufwtr, mdbuf)) = &pretty_data
&& bufwtr.print(&mdbuf).is_ok()
{
return;
}
// Everything failed. Print the raw markdown text.
safe_print!("{content}");
} }
fn process_rlink(sess: &Session, compiler: &interface::Compiler) { fn process_rlink(sess: &Session, compiler: &interface::Compiler) {