Merge commit 'd0cf3481a84e3aa68c2f185c460e282af36ebc42' into clippyup

[rust.git] / src / tools / clippy / clippy_utils / src / diagnostics.rs

diff --git a/src/tools/clippy/clippy_utils/src/diagnostics.rs b/src/tools/clippy/clippy_utils/src/diagnostics.rs
index a927788e6a44ad9931c8bc7521fdea5f4006fa5c..625a53899df94d69e0dbf8db91b9856ea677e69d 100644 (file)
--- a/src/tools/clippy/clippy_utils/src/diagnostics.rs
+++ b/src/tools/clippy/clippy_utils/src/diagnostics.rs
@@ -8,7 +8,7 @@
 //! Thank you!
 //! ~The `INTERNAL_METADATA_COLLECTOR` lint
 
-use rustc_errors::{Applicability, Diagnostic};
+use rustc_errors::{emitter::MAX_SUGGESTION_HIGHLIGHT_LINES, Applicability, Diagnostic};
 use rustc_hir::HirId;
 use rustc_lint::{LateContext, Lint, LintContext};
 use rustc_span::source_map::{MultiSpan, Span};
@@ -213,6 +213,90 @@ pub fn span_lint_and_sugg<'a, T: LintContext>(
     });
 }
 
+/// Like [`span_lint_and_sugg`] with a focus on the edges. The output will either
+/// emit single span or multispan suggestion depending on the number of its lines.
+///
+/// If the given suggestion string has more lines than the maximum display length defined by
+/// [`MAX_SUGGESTION_HIGHLIGHT_LINES`][`rustc_errors::emitter::MAX_SUGGESTION_HIGHLIGHT_LINES`],
+/// this function will split the suggestion and span to showcase the change for the top and
+/// bottom edge of the code. For normal suggestions, in one display window, the help message
+/// will be combined with a colon.
+///
+/// Multipart suggestions like the one being created here currently cannot be
+/// applied by rustfix (See [rustfix#141](https://github.com/rust-lang/rustfix/issues/141)).
+/// Testing rustfix with this lint emission function might require a file with
+/// suggestions that can be fixed and those that can't. See
+/// [clippy#8520](https://github.com/rust-lang/rust-clippy/pull/8520/files) for
+/// an example and of this.
+///
+/// # Example for a long suggestion
+///
+/// ```text
+/// error: called `map(..).flatten()` on `Option`
+///   --> $DIR/map_flatten.rs:8:10
+///    |
+/// LL |           .map(|x| {
+///    |  __________^
+/// LL | |             if x <= 5 {
+/// LL | |                 Some(x)
+/// LL | |             } else {
+/// ...  |
+/// LL | |         })
+/// LL | |         .flatten();
+///    | |__________________^
+///    |
+///   = note: `-D clippy::map-flatten` implied by `-D warnings`
+/// help: try replacing `map` with `and_then`
+///    |
+/// LL ~         .and_then(|x| {
+/// LL +             if x <= 5 {
+/// LL +                 Some(x)
+///    |
+/// help: and remove the `.flatten()`
+///    |
+/// LL +                 None
+/// LL +             }
+/// LL ~         });
+///    |
+/// ```
+pub fn span_lint_and_sugg_for_edges(
+    cx: &LateContext<'_>,
+    lint: &'static Lint,
+    sp: Span,
+    msg: &str,
+    helps: &[&str; 2],
+    sugg: String,
+    applicability: Applicability,
+) {
+    span_lint_and_then(cx, lint, sp, msg, |diag| {
+        let sugg_lines_count = sugg.lines().count();
+        if sugg_lines_count > MAX_SUGGESTION_HIGHLIGHT_LINES {
+            let sm = cx.sess().source_map();
+            if let (Ok(line_upper), Ok(line_bottom)) = (sm.lookup_line(sp.lo()), sm.lookup_line(sp.hi())) {
+                let split_idx = MAX_SUGGESTION_HIGHLIGHT_LINES / 2;
+                let span_upper = sm.span_until_char(sp.with_hi(line_upper.sf.lines[line_upper.line + split_idx]), '\n');
+                let span_bottom = sp.with_lo(line_bottom.sf.lines[line_bottom.line - split_idx]);
+
+                let sugg_lines_vec = sugg.lines().collect::<Vec<&str>>();
+                let sugg_upper = sugg_lines_vec[..split_idx].join("\n");
+                let sugg_bottom = sugg_lines_vec[sugg_lines_count - split_idx..].join("\n");
+
+                diag.span_suggestion(span_upper, helps[0], sugg_upper, applicability);
+                diag.span_suggestion(span_bottom, helps[1], sugg_bottom, applicability);
+
+                return;
+            }
+        }
+        diag.span_suggestion_with_style(
+            sp,
+            &helps.join(", "),
+            sugg,
+            applicability,
+            rustc_errors::SuggestionStyle::ShowAlways,
+        );
+    });
+}
+
 /// Create a suggestion made from several `span → replacement`.
 ///
 /// Note: in the JSON format (used by `compiletest_rs`), the help message will