Auto merge of #77671 - flip1995:lint_list_always_plugins, r=oli-obk,Manishearth

Always print lints from plugins, if they're available

Currently you can get a list of lints and lint groups by running `rustc
-Whelp`. This prints an additional line at the end:
```
Compiler plugins can provide additional lints and lint groups. To see a listing of these, re-run `rustc -W help` with a crate filename.
```

Clippy is such a "compiler plugin", that provides additional lints.
Running `clippy-driver -Whelp` (`rustc` wrapper) still only prints the
rustc lints with the above message at the end. But when running
`clippy-driver -Whelp main.rs`, where `main.rs` is any rust file, it
also prints Clippy lints. I don't think this is a good approach from a
UX perspective: Why is a random file necessary to print a help message?

This PR changes this behavior: Whenever a compiler callback
registers lints, it is assumed that these lints come from a plugin and
are printed without having to specify a Rust source file.

Fixes rust-lang/rust-clippy#6122

cc `@Manishearth` `@ebroto` for the Clippy changes.

clippy_dev/src/update_lints.rs

@@ -22,20 +22,7 @@ pub fn run(update_mode: UpdateMode) {
 
     let usable_lint_count = round_to_fifty(usable_lints.len());
 
-    let mut file_change = replace_region_in_file(
-        Path::new("src/lintlist/mod.rs"),
-        "begin lint list",
-        "end lint list",
-        false,
-        update_mode == UpdateMode::Change,
-        || {
-            format!("vec!{:#?}", sorted_usable_lints)
-                .lines()
-                .map(ToString::to_string)
-                .collect::<Vec<_>>()
-        },
-    )
-    .changed;
+    let mut file_change = false;
 
     file_change |= replace_region_in_file(
         Path::new("README.md"),

src/driver.rs

@@ -8,7 +8,6 @@
 
 // FIXME: switch to something more ergonomic here, once available.
 // (Currently there is no way to opt into sysroot crates without `extern crate`.)
-extern crate rustc_data_structures;
 extern crate rustc_driver;
 extern crate rustc_errors;
 extern crate rustc_interface;
@@ -26,8 +25,6 @@ use std::panic;
 use std::path::{Path, PathBuf};
 use std::process::{exit, Command};
 
-mod lintlist;
-
 /// If a command-line option matches `find_arg`, then apply the predicate `pred` on its value. If
 /// true, then return it. The parameter is assumed to be either `--arg=value` or `--arg value`.
 fn arg_value<'a, T: Deref<Target = str>>(
@@ -92,113 +89,6 @@ impl rustc_driver::Callbacks for ClippyCallbacks {
     }
 }
 
-#[allow(clippy::find_map, clippy::filter_map)]
-fn describe_lints() {
-    use lintlist::{Level, Lint, ALL_LINTS, LINT_LEVELS};
-    use rustc_data_structures::fx::FxHashSet;
-
-    println!(
-        "
-Available lint options:
-    -W <foo>           Warn about <foo>
-    -A <foo>           Allow <foo>
-    -D <foo>           Deny <foo>
-    -F <foo>           Forbid <foo> (deny <foo> and all attempts to override)
-
-"
-    );
-
-    let lint_level = |lint: &Lint| {
-        LINT_LEVELS
-            .iter()
-            .find(|level_mapping| level_mapping.0 == lint.group)
-            .map(|(_, level)| match level {
-                Level::Allow => "allow",
-                Level::Warn => "warn",
-                Level::Deny => "deny",
-            })
-            .unwrap()
-    };
-
-    let mut lints: Vec<_> = ALL_LINTS.iter().collect();
-    // The sort doesn't case-fold but it's doubtful we care.
-    lints.sort_by_cached_key(|x: &&Lint| (lint_level(x), x.name));
-
-    let max_lint_name_len = lints
-        .iter()
-        .map(|lint| lint.name.len())
-        .map(|len| len + "clippy::".len())
-        .max()
-        .unwrap_or(0);
-
-    let padded = |x: &str| {
-        let mut s = " ".repeat(max_lint_name_len - x.chars().count());
-        s.push_str(x);
-        s
-    };
-
-    let scoped = |x: &str| format!("clippy::{}", x);
-
-    let lint_groups: FxHashSet<_> = lints.iter().map(|lint| lint.group).collect();
-
-    println!("Lint checks provided by clippy:\n");
-    println!("    {}  {:7.7}  meaning", padded("name"), "default");
-    println!("    {}  {:7.7}  -------", padded("----"), "-------");
-
-    let print_lints = |lints: &[&Lint]| {
-        for lint in lints {
-            let name = lint.name.replace("_", "-");
-            println!(
-                "    {}  {:7.7}  {}",
-                padded(&scoped(&name)),
-                lint_level(lint),
-                lint.desc
-            );
-        }
-        println!("\n");
-    };
-
-    print_lints(&lints);
-
-    let max_group_name_len = std::cmp::max(
-        "clippy::all".len(),
-        lint_groups
-            .iter()
-            .map(|group| group.len())
-            .map(|len| len + "clippy::".len())
-            .max()
-            .unwrap_or(0),
-    );
-
-    let padded_group = |x: &str| {
-        let mut s = " ".repeat(max_group_name_len - x.chars().count());
-        s.push_str(x);
-        s
-    };
-
-    println!("Lint groups provided by clippy:\n");
-    println!("    {}  sub-lints", padded_group("name"));
-    println!("    {}  ---------", padded_group("----"));
-    println!("    {}  the set of all clippy lints", padded_group("clippy::all"));
-
-    let print_lint_groups = || {
-        for group in lint_groups {
-            let name = group.to_lowercase().replace("_", "-");
-            let desc = lints
-                .iter()
-                .filter(|&lint| lint.group == group)
-                .map(|lint| lint.name)
-                .map(|name| name.replace("_", "-"))
-                .collect::<Vec<String>>()
-                .join(", ");
-            println!("    {}  {}", padded_group(&scoped(&name)), desc);
-        }
-        println!("\n");
-    };
-
-    print_lint_groups();
-}
-
 fn display_help() {
     println!(
         "\
@@ -379,17 +269,6 @@ pub fn main() {
             exit(0);
         }
 
-        let should_describe_lints = || {
-            let args: Vec<_> = env::args().collect();
-            args.windows(2)
-                .any(|args| args[1] == "help" && matches!(args[0].as_str(), "-W" | "-A" | "-D" | "-F"))
-        };
-
-        if !wrapper_mode && should_describe_lints() {
-            describe_lints();
-            exit(0);
-        }
-
         // this conditional check for the --sysroot flag is there so users can call
         // `clippy_driver` directly
         // without having to pass --sysroot or anything

src/lintlist/lint.rs

@@ -1,27 +0,0 @@
-/// Lint data parsed from the Clippy source code.
-#[derive(Clone, PartialEq, Debug)]
-pub struct Lint {
-    pub name: &'static str,
-    pub group: &'static str,
-    pub desc: &'static str,
-    pub deprecation: Option<&'static str>,
-    pub module: &'static str,
-}
-
-#[derive(PartialOrd, PartialEq, Ord, Eq)]
-pub enum Level {
-    Allow,
-    Warn,
-    Deny,
-}
-
-pub const LINT_LEVELS: [(&str, Level); 8] = [
-    ("correctness", Level::Deny),
-    ("style", Level::Warn),
-    ("complexity", Level::Warn),
-    ("perf", Level::Warn),
-    ("restriction", Level::Allow),
-    ("pedantic", Level::Allow),
-    ("nursery", Level::Allow),
-    ("cargo", Level::Allow),
-];