make unknown features on cargo add more discoverable

src/cargo/ops/cargo_add/mod.rs

@@ -11,6 +11,7 @@ use std::path::Path;
 use anyhow::Context as _;
 use cargo_util::paths;
 use indexmap::IndexSet;
+use itertools::Itertools;
 use termcolor::Color::Green;
 use termcolor::Color::Red;
 use termcolor::ColorSpec;
@@ -101,7 +102,6 @@ pub fn add(workspace: &Workspace<'_>, options: &AddOptions<'_>) -> CargoResult<(
         });
     for dep in deps {
         print_action_msg(&mut options.config.shell(), &dep, &dep_table)?;
-        print_dep_table_msg(&mut options.config.shell(), &dep)?;
         if let Some(Source::Path(src)) = dep.source() {
             if src.path == manifest.path.parent().unwrap_or_else(|| Path::new("")) {
                 anyhow::bail!(
@@ -126,11 +126,66 @@ pub fn add(workspace: &Workspace<'_>, options: &AddOptions<'_>) -> CargoResult<(
                 inherited_features.iter().map(|s| s.as_str()).collect();
             unknown_features.extend(inherited_features.difference(&available_features).copied());
         }
+
         unknown_features.sort();
+
         if !unknown_features.is_empty() {
-            anyhow::bail!("unrecognized features: {unknown_features:?}");
+            let (activated, deactivated) = dep.features();
+            let deactivated = deactivated
+                .iter()
+                .filter(|f| !unknown_features.contains(f))
+                .collect::<Vec<_>>();
+            let activated = activated
+                .iter()
+                .filter(|f| !unknown_features.contains(f))
+                .collect::<Vec<_>>();
+            let mut message = format!(
+                "unrecognized feature{} for crate {}: {}\n",
+                if unknown_features.len() == 1 { "" } else { "s" },
+                dep.name,
+                unknown_features.iter().format(", "),
+            );
+            if activated.is_empty() && deactivated.is_empty() {
+                write!(message, "no features available for crate {}", dep.name)?;
+            } else {
+                if !deactivated.is_empty() {
+                    writeln!(
+                        message,
+                        "disabled features:\n    {}",
+                        deactivated
+                            .iter()
+                            .map(|s| s.to_string())
+                            .coalesce(|x, y| if x.len() + y.len() < 78 {
+                                Ok(format!("{x}, {y}"))
+                            } else {
+                                Err((x, y))
+                            })
+                            .into_iter()
+                            .format("\n    ")
+                    )?
+                }
+                if !activated.is_empty() {
+                    writeln!(
+                        message,
+                        "enabled features:\n    {}",
+                        activated
+                            .iter()
+                            .map(|s| s.to_string())
+                            .coalesce(|x, y| if x.len() + y.len() < 78 {
+                                Ok(format!("{x}, {y}"))
+                            } else {
+                                Err((x, y))
+                            })
+                            .into_iter()
+                            .format("\n    ")
+                    )?
+                }
+            }
+            anyhow::bail!(message.trim().to_owned());
         }
 
+        print_dep_table_msg(&mut options.config.shell(), &dep)?;
+
         manifest.insert_into_table(&dep_table, &dep)?;
         manifest.gc_dep(dep.toml_key());
     }

tests/testsuite/cargo_add/features_unknown/mod.rs

@@ -23,3 +23,22 @@ fn features_unknown() {
 
     assert_ui().subset_matches(curr_dir!().join("out"), &project_root);
 }
+
+#[cargo_test]
+fn features_unknown_empty() {
+    init_registry();
+    let project = Project::from_template(curr_dir!().join("in"));
+    let project_root = project.root();
+    let cwd = &project_root;
+
+    snapbox::cmd::Command::cargo_ui()
+        .arg("add")
+        .arg_line("my-package --features noze")
+        .current_dir(cwd)
+        .assert()
+        .code(101)
+        .stdout_matches_path(curr_dir!().join("stdout_no_features.log"))
+        .stderr_matches_path(curr_dir!().join("stderr_no_features.log"));
+
+    assert_ui().subset_matches(curr_dir!().join("out"), &project_root);
+}

tests/testsuite/cargo_add/features_unknown/stderr.log

@@ -1,9 +1,5 @@
     Updating `dummy-registry` index
       Adding your-face v99999.0.0 to dependencies.
-             Features:
-             + noze
-             - ears
-             - eyes
-             - mouth
-             - nose
-error: unrecognized features: ["noze"]
+error: unrecognized feature for crate your-face: noze
+disabled features:
+    ears, eyes, mouth, nose

tests/testsuite/cargo_add/features_unknown/stderr_no_features.log

@@ -0,0 +1,4 @@
+    Updating `dummy-registry` index
+      Adding my-package v99999.0.0 to dependencies.
+error: unrecognized feature for crate my-package: noze
+no features available for crate my-package

tests/testsuite/cargo_add/unknown_inherited_feature/in/dependency/Cargo.toml

@@ -6,9 +6,15 @@ version = "0.0.0"
 default-base = []
 default-test-base = []
 default-merge-base = []
-default = ["default-base", "default-test-base", "default-merge-base"]
+long-feature-name-because-of-formatting-reasons = []
+default = [
+    "default-base",
+    "default-test-base",
+    "default-merge-base",
+    "long-feature-name-because-of-formatting-reasons",
+]
 test-base = []
 test = ["test-base", "default-test-base"]
 merge-base = []
 merge = ["merge-base", "default-merge-base"]
-unrelated = []
+unrelated = []

tests/testsuite/cargo_add/unknown_inherited_feature/out/dependency/Cargo.toml

@@ -6,9 +6,15 @@ version = "0.0.0"
 default-base = []
 default-test-base = []
 default-merge-base = []
-default = ["default-base", "default-test-base", "default-merge-base"]
+long-feature-name-because-of-formatting-reasons = []
+default = [
+    "default-base",
+    "default-test-base",
+    "default-merge-base",
+    "long-feature-name-because-of-formatting-reasons",
+]
 test-base = []
 test = ["test-base", "default-test-base"]
 merge-base = []
 merge = ["merge-base", "default-merge-base"]
-unrelated = []
+unrelated = []

tests/testsuite/cargo_add/unknown_inherited_feature/stderr.log

@@ -1,12 +1,7 @@
       Adding foo (workspace) to dependencies.
-             Features as of v0.0.0:
-             + default-base
-             + default-merge-base
-             + default-test-base
-             + not_recognized
-             + test
-             + test-base
-             - merge
-             - merge-base
-             - unrelated
-error: unrecognized features: ["not_recognized"]
+error: unrecognized feature for crate foo: not_recognized
+disabled features:
+    merge, merge-base, unrelated
+enabled features:
+    default-base, default-merge-base, default-test-base
+    long-feature-name-because-of-formatting-reasons, test, test-base