Auto merge of #14436 - kornelski:where-are-the-features, r=epage

More helpful missing feature error message

The "none of the selected packages contains these features" error does not say which packages are selected, and does not say which packages do have the requested features.

If any package in the workspace has the requested feature (matching exactly), the error suggests selecting that package, instead of trying alternative spellings.

src/cargo/core/workspace.rs

@@ -1363,12 +1363,12 @@ impl<'gctx> Workspace<'gctx> {
         }
     }
 
-    fn report_unknown_features_error(
+    fn missing_feature_spelling_suggestions(
         &self,
-        specs: &[PackageIdSpec],
+        selected_members: &[&Package],
         cli_features: &CliFeatures,
         found_features: &BTreeSet<FeatureValue>,
-    ) -> CargoResult<()> {
+    ) -> Vec<String> {
         // Keeps track of which features were contained in summary of `member` to suggest similar features in errors
         let mut summary_features: Vec<InternedString> = Default::default();
 
@@ -1387,10 +1387,7 @@ impl<'gctx> Workspace<'gctx> {
         let mut optional_dependency_names_per_member: BTreeMap<&Package, BTreeSet<InternedString>> =
             Default::default();
 
-        for member in self
-            .members()
-            .filter(|m| specs.iter().any(|spec| spec.matches(m.package_id())))
-        {
+        for &member in selected_members {
             // Only include features this member defines.
             let summary = member.summary();
 
@@ -1428,7 +1425,7 @@ impl<'gctx> Workspace<'gctx> {
             edit_distance(a.as_str(), b.as_str(), 3).is_some()
         };
 
-        let suggestions: Vec<_> = cli_features
+        cli_features
             .features
             .difference(found_features)
             .map(|feature| match feature {
@@ -1522,27 +1519,86 @@ impl<'gctx> Workspace<'gctx> {
             })
             .sorted()
             .take(5)
-            .collect();
+            .collect()
+    }
 
+    fn report_unknown_features_error(
+        &self,
+        specs: &[PackageIdSpec],
+        cli_features: &CliFeatures,
+        found_features: &BTreeSet<FeatureValue>,
+    ) -> CargoResult<()> {
         let unknown: Vec<_> = cli_features
             .features
             .difference(found_features)
             .map(|feature| feature.to_string())
             .sorted()
             .collect();
 
-        if suggestions.is_empty() {
-            bail!(
-                "none of the selected packages contains these features: {}",
+        let (selected_members, unselected_members): (Vec<_>, Vec<_>) = self
+            .members()
+            .partition(|member| specs.iter().any(|spec| spec.matches(member.package_id())));
+
+        let missing_packages_with_the_features = unselected_members
+            .into_iter()
+            .filter(|member| {
+                unknown
+                    .iter()
+                    .any(|feature| member.summary().features().contains_key(&**feature))
+            })
+            .map(|m| m.name())
+            .collect_vec();
+
+        let these_features = if unknown.len() == 1 {
+            "this feature"
+        } else {
+            "these features"
+        };
+        let mut msg = if let [singular] = &selected_members[..] {
+            format!(
+                "the package '{}' does not contain {these_features}: {}",
+                singular.name(),
                 unknown.join(", ")
-            );
+            )
         } else {
-            bail!(
-                "none of the selected packages contains these features: {}, did you mean: {}?",
-                unknown.join(", "),
-                suggestions.join(", ")
+            let names = selected_members.iter().map(|m| m.name()).join(", ");
+            format!("none of the selected packages contains {these_features}: {}\nselected packages: {names}", unknown.join(", "))
+        };
+
+        use std::fmt::Write;
+        if !missing_packages_with_the_features.is_empty() {
+            write!(
+                &mut msg,
+                "\nhelp: package{} with the missing feature{}: {}",
+                if missing_packages_with_the_features.len() != 1 {
+                    "s"
+                } else {
+                    ""
+                },
+                if unknown.len() != 1 { "s" } else { "" },
+                missing_packages_with_the_features.join(", ")
+            )?;
+        } else {
+            let suggestions = self.missing_feature_spelling_suggestions(
+                &selected_members,
+                cli_features,
+                found_features,
             );
+            if !suggestions.is_empty() {
+                write!(
+                    &mut msg,
+                    "\nhelp: there {}: {}",
+                    if suggestions.len() == 1 {
+                        "is a similarly named feature"
+                    } else {
+                        "are similarly named features"
+                    },
+                    suggestions.join(", ")
+                )?;
+            }
         }
+
+        bail!("{msg}")
     }
 
     /// New command-line feature selection behavior with resolver = "2" or the

tests/testsuite/package_features.rs

@@ -75,31 +75,48 @@ fn virtual_no_default_features() {
     p.cargo("check --features foo")
         .with_status(101)
         .with_stderr_data(str![[r#"
-[ERROR] none of the selected packages contains these features: foo, did you mean: f1?
+[ERROR] none of the selected packages contains this feature: foo
+selected packages: a, b
+[HELP] there is a similarly named feature: f1
 
 "#]])
         .run();
 
     p.cargo("check --features a/dep1,b/f1,b/f2,f2")
         .with_status(101)
         .with_stderr_data(str![[r#"
-[ERROR] none of the selected packages contains these features: b/f2, f2, did you mean: f1?
+[ERROR] none of the selected packages contains these features: b/f2, f2
+selected packages: a, b
+[HELP] there is a similarly named feature: f1
 
 "#]])
         .run();
 
     p.cargo("check --features a/dep,b/f1,b/f2,f2")
         .with_status(101)
         .with_stderr_data(str![[r#"
-[ERROR] none of the selected packages contains these features: a/dep, b/f2, f2, did you mean: a/dep1, f1?
+[ERROR] none of the selected packages contains these features: a/dep, b/f2, f2
+selected packages: a, b
+[HELP] there are similarly named features: a/dep1, f1
 
 "#]])
         .run();
 
     p.cargo("check --features a/dep,a/dep1")
         .with_status(101)
         .with_stderr_data(str![[r#"
-[ERROR] none of the selected packages contains these features: a/dep, did you mean: b/f1?
+[ERROR] none of the selected packages contains this feature: a/dep
+selected packages: a, b
+[HELP] there is a similarly named feature: b/f1
+
+"#]])
+        .run();
+
+    p.cargo("check -p b --features=dep1")
+        .with_status(101)
+        .with_stderr_data(str![[r#"
+[ERROR] the package 'b' does not contain this feature: dep1
+[HELP] package with the missing feature: a
 
 "#]])
         .run();
@@ -126,7 +143,8 @@ fn virtual_typo_member_feature() {
         .cargo("check --features a/deny-warning")
         .with_status(101)
         .with_stderr_data(str![[r#"
-[ERROR] none of the selected packages contains these features: a/deny-warning, did you mean: a/deny-warnings?
+[ERROR] the package 'a' does not contain this feature: a/deny-warning
+[HELP] there is a similarly named feature: a/deny-warnings
 
 "#]])
         .run();