Avoid saving the same future_incompat warning multiple times

src/cargo/core/compiler/future_incompat.rs

@@ -100,18 +100,30 @@ impl Default for OnDiskReports {
 }
 
 impl OnDiskReports {
- /// Saves a new report.
+ /// Saves a new report returning its id
  pub fn save_report(
  mut self,
  ws: &Workspace<'_>,
  suggestion_message: String,
  per_package_reports: &[FutureIncompatReportPackage],
- ) {
+ ) -> u32 {
+ let per_package = render_report(per_package_reports);
+
+ if let Some(existing_report) = self
+ .reports
+ .iter()
+ .find(|existing| existing.per_package == per_package)
+ {
+ return existing_report.id;
+ }
+
  let report = OnDiskReport {
  id: self.next_id,
  suggestion_message,
- per_package: render_report(per_package_reports),
+ per_package,
  };
+
+ let saved_id = report.id;
  self.next_id += 1;
  self.reports.push(report);
  if self.reports.len() > MAX_REPORTS {
@@ -138,6 +150,8 @@ impl OnDiskReports {
  &mut ws.config().shell(),
  );
  }
+
+ saved_id
  }
 
  /// Loads the on-disk reports.
@@ -450,7 +464,7 @@ https://doc.rust-lang.org/cargo/reference/overriding-dependencies.html#the-patch
  update_message = update_message,
  );
 
- current_reports.save_report(
+ let saved_report_id = current_reports.save_report(
  bcx.ws,
  suggestion_message.clone(),
  per_package_future_incompat_reports,
@@ -461,14 +475,14 @@ https://doc.rust-lang.org/cargo/reference/overriding-dependencies.html#the-patch
  drop(bcx.config.shell().note(&format!(
  "this report can be shown with `cargo report \
  future-incompatibilities --id {}`",
- report_id
+ saved_report_id
  )));
  } else if should_display_message {
  drop(bcx.config.shell().note(&format!(
  "to see what the problems were, use the option \
  `--future-incompat-report`, or run `cargo report \
  future-incompatibilities --id {}`",
- report_id
+ saved_report_id
  )));
  }
 }