lint-docs: Add --validate flag to validate lint docs separately.

compiler/rustc_lint_defs/src/lib.rs

@@ -366,11 +366,25 @@ impl LintBuffer {
 /// ```
 ///
 /// The `{{produces}}` tag will be automatically replaced with the output from
-/// the example by the build system. You can build and view the rustc book
-/// with `x.py doc --stage=1 src/doc/rustc --open`. If the lint example is too
-/// complex to run as a simple example (for example, it needs an extern
-/// crate), mark it with `ignore` and manually paste the expected output below
-/// the example.
+/// the example by the build system. If the lint example is too complex to run
+/// as a simple example (for example, it needs an extern crate), mark the code
+/// block with `ignore` and manually replace the `{{produces}}` line with the
+/// expected output in a `text` code block.
+///
+/// If this is a rustdoc-only lint, then only include a brief introduction
+/// with a link with the text `[rustdoc book]` so that the validator knows
+/// that this is for rustdoc only (see BROKEN_INTRA_DOC_LINKS as an example).
+///
+/// Commands to view and test the documentation:
+///
+/// * `./x.py doc --stage=1 src/doc/rustc --open`: Builds the rustc book and opens it.
+/// * `./x.py test src/tools/lint-docs`: Validates that the lint docs have the
+///   correct style, and that the code example actually emits the expected
+///   lint.
+///
+/// If you have already built the compiler, and you want to make changes to
+/// just the doc comments, then use the `--keep-stage=0` flag with the above
+/// commands to avoid rebuilding the compiler.
 #[macro_export]
 macro_rules! declare_lint {
     ($(#[$attr:meta])* $vis: vis $NAME: ident, $Level: ident, $desc: expr) => (

src/bootstrap/builder.rs

@@ -413,6 +413,7 @@ impl<'a> Builder<'a> {
                 test::TheBook,
                 test::UnstableBook,
                 test::RustcBook,
+                test::LintDocs,
                 test::RustcGuide,
                 test::EmbeddedBook,
                 test::EditionGuide,

src/bootstrap/doc.rs

@@ -726,6 +726,7 @@ fn symlink_dir_force(config: &Config, src: &Path, dst: &Path) -> io::Result<()>
 pub struct RustcBook {
     pub compiler: Compiler,
     pub target: TargetSelection,
+    pub validate: bool,
 }
 
 impl Step for RustcBook {
@@ -742,6 +743,7 @@ impl Step for RustcBook {
         run.builder.ensure(RustcBook {
             compiler: run.builder.compiler(run.builder.top_stage, run.builder.config.build),
             target: run.target,
+            validate: false,
         });
     }
 
@@ -772,6 +774,9 @@ impl Step for RustcBook {
         if builder.config.verbose() {
             cmd.arg("--verbose");
         }
+        if self.validate {
+            cmd.arg("--validate");
+        }
         // If the lib directories are in an unusual location (changed in
         // config.toml), then this needs to explicitly update the dylib search
         // path.

src/bootstrap/test.rs

@@ -2115,3 +2115,36 @@ impl Step for TierCheck {
         try_run(builder, &mut cargo.into());
     }
 }
+
+#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
+pub struct LintDocs {
+    pub compiler: Compiler,
+    pub target: TargetSelection,
+}
+
+impl Step for LintDocs {
+    type Output = ();
+    const DEFAULT: bool = true;
+    const ONLY_HOSTS: bool = true;
+
+    fn should_run(run: ShouldRun<'_>) -> ShouldRun<'_> {
+        run.path("src/tools/lint-docs")
+    }
+
+    fn make_run(run: RunConfig<'_>) {
+        run.builder.ensure(LintDocs {
+            compiler: run.builder.compiler(run.builder.top_stage, run.builder.config.build),
+            target: run.target,
+        });
+    }
+
+    /// Tests that the lint examples in the rustc book generate the correct
+    /// lints and have the expected format.
+    fn run(self, builder: &Builder<'_>) {
+        builder.ensure(crate::doc::RustcBook {
+            compiler: self.compiler,
+            target: self.target,
+            validate: true,
+        });
+    }
+}

src/tools/lint-docs/src/groups.rs

@@ -5,6 +5,7 @@ use std::fmt::Write;
 use std::fs;
 use std::process::Command;
 
+/// Descriptions of rustc lint groups.
 static GROUP_DESCRIPTIONS: &[(&str, &str)] = &[
     ("unused", "Lints that detect things being declared but not used, or excess syntax"),
     ("rustdoc", "Rustdoc-specific lints"),
@@ -86,17 +87,27 @@ impl<'a> LintExtractor<'a> {
         result.push_str("|-------|-------------|-------|\n");
         result.push_str("| warnings | All lints that are set to issue warnings | See [warn-by-default] for the default set of warnings |\n");
         for (group_name, group_lints) in groups {
-            let description = GROUP_DESCRIPTIONS
-                .iter()
-                .find(|(n, _)| n == group_name)
-                .ok_or_else(|| {
-                    format!(
+            let description = match GROUP_DESCRIPTIONS.iter().find(|(n, _)| n == group_name) {
+                Some((_, desc)) => desc,
+                None if self.validate => {
+                    return Err(format!(
                         "lint group `{}` does not have a description, \
-                         please update the GROUP_DESCRIPTIONS list",
+                         please update the GROUP_DESCRIPTIONS list in \
+                         src/tools/lint-docs/src/groups.rs",
                         group_name
                     )
-                })?
-                .1;
+                    .into());
+                }
+                None => {
+                    eprintln!(
+                        "warning: lint group `{}` is missing from the GROUP_DESCRIPTIONS list\n\
+                         If this is a new lint group, please update the GROUP_DESCRIPTIONS in \
+                         src/tools/lint-docs/src/groups.rs",
+                        group_name
+                    );
+                    continue;
+                }
+            };
             to_link.extend(group_lints);
             let brackets: Vec<_> = group_lints.iter().map(|l| format!("[{}]", l)).collect();
             write!(result, "| {} | {} | {} |\n", group_name, description, brackets.join(", "))

src/tools/lint-docs/src/lib.rs

@@ -19,6 +19,8 @@ pub struct LintExtractor<'a> {
     pub rustc_target: &'a str,
     /// Verbose output.
     pub verbose: bool,
+    /// Validate the style and the code example.
+    pub validate: bool,
 }
 
 struct Lint {
@@ -122,7 +124,7 @@ impl<'a> LintExtractor<'a> {
         let contents = fs::read_to_string(path)
             .map_err(|e| format!("could not read {}: {}", path.display(), e))?;
         let mut lines = contents.lines().enumerate();
-        loop {
+        'outer: loop {
             // Find a lint declaration.
             let lint_start = loop {
                 match lines.next() {
@@ -158,12 +160,22 @@ impl<'a> LintExtractor<'a> {
                                 )
                             })?;
                             if doc_lines.is_empty() {
-                                return Err(format!(
-                                    "did not find doc lines for lint `{}` in {}",
-                                    name,
-                                    path.display()
-                                )
-                                .into());
+                                if self.validate {
+                                    return Err(format!(
+                                        "did not find doc lines for lint `{}` in {}",
+                                        name,
+                                        path.display()
+                                    )
+                                    .into());
+                                } else {
+                                    eprintln!(
+                                        "warning: lint `{}` in {} does not define any doc lines, \
+                                         these are required for the lint documentation",
+                                        name,
+                                        path.display()
+                                    );
+                                    continue 'outer;
+                                }
                             }
                             break (doc_lines, name);
                         }
@@ -234,13 +246,26 @@ impl<'a> LintExtractor<'a> {
             // Rustdoc lints are documented in the rustdoc book, don't check these.
             return Ok(());
         }
-        lint.check_style()?;
+        if self.validate {
+            lint.check_style()?;
+        }
         // Unfortunately some lints have extra requirements that this simple test
         // setup can't handle (like extern crates). An alternative is to use a
         // separate test suite, and use an include mechanism such as mdbook's
         // `{{#rustdoc_include}}`.
         if !lint.is_ignored() {
-            self.replace_produces(lint)?;
+            if let Err(e) = self.replace_produces(lint) {
+                if self.validate {
+                    return Err(e);
+                }
+                eprintln!(
+                    "warning: the code example in lint `{}` in {} failed to \
+                     generate the expected output: {}",
+                    lint.name,
+                    lint.path.display(),
+                    e
+                );
+            }
         }
         Ok(())
     }

src/tools/lint-docs/src/main.rs

@@ -3,7 +3,7 @@ use std::path::PathBuf;
 
 fn main() {
     if let Err(e) = doit() {
-        println!("error: {}", e);
+        eprintln!("error: {}", e);
         std::process::exit(1);
     }
 }
@@ -15,6 +15,7 @@ fn doit() -> Result<(), Box<dyn Error>> {
     let mut rustc_path = None;
     let mut rustc_target = None;
     let mut verbose = false;
+    let mut validate = false;
     while let Some(arg) = args.next() {
         match arg.as_str() {
             "--src" => {
@@ -42,6 +43,7 @@ fn doit() -> Result<(), Box<dyn Error>> {
                 };
             }
             "-v" | "--verbose" => verbose = true,
+            "--validate" => validate = true,
             s => return Err(format!("unexpected argument `{}`", s).into()),
         }
     }
@@ -63,6 +65,7 @@ fn doit() -> Result<(), Box<dyn Error>> {
         rustc_path: &rustc_path.unwrap(),
         rustc_target: &rustc_target.unwrap(),
         verbose,
+        validate,
     };
     le.extract_lint_docs()
 }