fix(run): Disambiguate bins from different packages that share a name (#15298)

### What does this PR try to resolve?

This builds on the work done in #15199 to improve target selection
errors to also disambiguate when the same binary name is used in
multiple packages.

This also makes the errors from #15199 more consistent with the rustc
style guide and reduces code duplication.

Fixes #13312

### How should we test and review this PR?

This is a first pass and does not do the full `--package foo --bin bar`
syntax. I wanted to focus on the basic functionality before we iterated
on it, e.g. investigating how well we can predict the CLI flags, how
much noise they might add, etc.

### Additional information

src/cargo/ops/cargo_compile/unit_generator.rs

@@ -259,24 +259,27 @@ impl<'a> UnitGenerator<'a, '_> {
         };
         let proposals = self.filter_targets(filter, true, mode);
         if proposals.is_empty() {
-            let targets = self
+            let mut targets = std::collections::BTreeMap::new();
-                .packages
+            for (pkg, target) in self.packages.iter().flat_map(|pkg| {
-                .iter()
-                .flat_map(|pkg| {
                 pkg.targets()
                     .iter()
                     .filter(|target| is_expected_kind(target))
-                })
+                    .map(move |t| (pkg, t))
-                .collect::<Vec<_>>();
+            }) {
-            let suggestion = closest_msg(target_name, targets.iter(), |t| t.name(), "target");
+                targets
+                    .entry(target.name())
+                    .or_insert_with(Vec::new)
+                    .push((pkg, target));
+            }
+
+            let suggestion = closest_msg(target_name, targets.keys(), |t| t, "target");
             let targets_elsewhere = self.get_targets_from_other_packages(filter)?;
-            let need_append_targets_elsewhere = !targets_elsewhere.is_empty();
+            let append_targets_elsewhere = |msg: &mut String| {
-            let append_targets_elsewhere = |msg: &mut String, prefix: &str| {
                 let mut available_msg = Vec::new();
-                for (package, targets) in targets_elsewhere {
+                for (package, targets) in &targets_elsewhere {
                     if !targets.is_empty() {
                         available_msg.push(format!(
-                            "help: Available {target_desc} in `{package}` package:"
+                            "help: available {target_desc} in `{package}` package:"
                         ));
                         for target in targets {
                             available_msg.push(format!("    {target}"));
@@ -284,12 +287,12 @@ impl<'a> UnitGenerator<'a, '_> {
                     }
                 }
                 if !available_msg.is_empty() {
-                    write!(msg, "{prefix}{}", available_msg.join("\n"))?;
+                    write!(msg, "\n{}", available_msg.join("\n"))?;
                 }
                 CargoResult::Ok(())
             };
 
-            let unmatched_packages = || match self.spec {
+            let unmatched_packages = match self.spec {
                 Packages::Default | Packages::OptOut(_) | Packages::All(_) => {
                     "default-run packages".to_owned()
                 }
@@ -305,33 +308,25 @@ impl<'a> UnitGenerator<'a, '_> {
                 }
             };
 
+            let named = if is_glob { "matches pattern" } else { "named" };
+
             let mut msg = String::new();
-            if !suggestion.is_empty() {
             write!(
                 msg,
-                    "no {} target {} `{}` in {}{}",
+                "no {target_desc} target {named} `{target_name}` in {unmatched_packages}{suggestion}",
-                    target_desc,
-                    if is_glob { "matches pattern" } else { "named" },
-                    target_name,
-                    unmatched_packages(),
-                    suggestion,
             )?;
-                append_targets_elsewhere(&mut msg, "\n")?;
+            if !targets_elsewhere.is_empty() {
+                append_targets_elsewhere(&mut msg)?;
+            } else if suggestion.is_empty() && !targets.is_empty() {
+                write!(msg, "\nhelp: available {} targets:", target_desc)?;
+                for (target_name, pkgs) in targets {
+                    if pkgs.len() == 1 {
+                        write!(msg, "\n    {target_name}")?;
                     } else {
-                writeln!(
+                        for (pkg, _) in pkgs {
-                    msg,
+                            let pkg_name = pkg.name();
-                    "no {} target {} `{}` in {}.",
+                            write!(msg, "\n    {target_name} in package {pkg_name}")?;
-                    target_desc,
+                        }
-                    if is_glob { "matches pattern" } else { "named" },
-                    target_name,
-                    unmatched_packages()
-                )?;
-
-                append_targets_elsewhere(&mut msg, "")?;
-                if !targets.is_empty() && !need_append_targets_elsewhere {
-                    writeln!(msg, "Available {} targets:", target_desc)?;
-                    for target in targets {
-                        writeln!(msg, "    {}", target.name())?;
                     }
                 }
             }

src/cargo/ops/cargo_run.rs

@@ -1,4 +1,5 @@
 use std::ffi::OsString;
+use std::fmt::Write as _;
 use std::iter;
 use std::path::Path;
 
@@ -69,10 +70,20 @@ pub fn run(
                 names.join(", ")
             )
         } else {
-            anyhow::bail!(
+            let mut message = "`cargo run` can run at most one executable, but \
-                "`cargo run` can run at most one executable, but \
                  multiple were specified"
-            )
+                .to_owned();
+            write!(&mut message, "\nhelp: available targets:")?;
+            for (pkg, bin) in &bins {
+                write!(
+                    &mut message,
+                    "\n    {} `{}` in package `{}`",
+                    bin.kind().description(),
+                    bin.name(),
+                    pkg.name()
+                )?;
+            }
+            anyhow::bail!(message)
         }
     }
 

tests/testsuite/build.rs

@@ -1337,11 +1337,10 @@ fn cargo_compile_with_filename() {
     p.cargo("build --bin bin.rs")
         .with_status(101)
         .with_stderr_data(str![[r#"
-[ERROR] no bin target named `bin.rs` in default-run packages.
+[ERROR] no bin target named `bin.rs` in default-run packages
-Available bin targets:
+[HELP] available bin targets:
     a
 
-
 "#]])
         .run();
 
@@ -1358,11 +1357,10 @@ Available bin targets:
     p.cargo("build --example example.rs")
         .with_status(101)
         .with_stderr_data(str![[r#"
-[ERROR] no example target named `example.rs` in default-run packages.
+[ERROR] no example target named `example.rs` in default-run packages
-Available example targets:
+[HELP] available example targets:
     a
 
-
 "#]])
         .run();
 

tests/testsuite/run.rs

@@ -623,11 +623,10 @@ automatically infer them to be a target, such as in subfolders.
 
 For more information on this warning you can consult
 https://github.com/rust-lang/cargo/issues/5330
-[ERROR] no example target named `a` in default-run packages.
+[ERROR] no example target named `a` in default-run packages
-Available example targets:
+[HELP] available example targets:
     do_magic
 
-
 "#]])
         .run();
 }
@@ -655,11 +654,10 @@ fn run_example_autodiscover_2015_with_autoexamples_disabled() {
     p.cargo("run --example a")
         .with_status(101)
         .with_stderr_data(str![[r#"
-[ERROR] no example target named `a` in default-run packages.
+[ERROR] no example target named `a` in default-run packages
-Available example targets:
+[HELP] available example targets:
     do_magic
 
-
 "#]])
         .run();
 }
@@ -743,11 +741,10 @@ fn run_with_filename() {
     p.cargo("run --bin bin.rs")
         .with_status(101)
         .with_stderr_data(str![[r#"
-[ERROR] no bin target named `bin.rs` in default-run packages.
+[ERROR] no bin target named `bin.rs` in default-run packages
-Available bin targets:
+[HELP] available bin targets:
     a
 
-
 "#]])
         .run();
 
@@ -764,11 +761,10 @@ Available bin targets:
     p.cargo("run --example example.rs")
         .with_status(101)
         .with_stderr_data(str![[r#"
-[ERROR] no example target named `example.rs` in default-run packages.
+[ERROR] no example target named `example.rs` in default-run packages
-Available example targets:
+[HELP] available example targets:
     a
 
-
 "#]])
         .run();
 
@@ -783,6 +779,235 @@ Available example targets:
         .run();
 }
 
+#[cargo_test]
+fn ambiguous_bin_name() {
+    let p = project()
+        .file(
+            "Cargo.toml",
+            r#"
+        [workspace]
+        resolver = "3"
+        members = ["crate1", "crate2", "crate3", "crate4"]
+        "#,
+        )
+        .file("crate1/src/bin/ambiguous.rs", "fn main(){}")
+        .file(
+            "crate1/Cargo.toml",
+            r#"
+        [package]
+        name = "crate1"
+        version = "0.1.0"
+        edition = "2024"
+    "#,
+        )
+        .file("crate2/src/bin/ambiguous.rs", "fn main(){}")
+        .file(
+            "crate2/Cargo.toml",
+            r#"
+        [package]
+        name = "crate2"
+        version = "0.1.0"
+        edition = "2024"
+    "#,
+        )
+        .file("crate3/src/bin/ambiguous.rs", "fn main(){}")
+        .file(
+            "crate3/Cargo.toml",
+            r#"
+        [package]
+        name = "crate3"
+        version = "0.1.0"
+        edition = "2024"
+    "#,
+        )
+        .file("crate4/src/bin/ambiguous.rs", "fn main(){}")
+        .file(
+            "crate4/Cargo.toml",
+            r#"
+        [package]
+        name = "crate4"
+        version = "0.1.0"
+        edition = "2024"
+    "#,
+        );
+    let p = p.build();
+
+    p.cargo("run --bin ambiguous")
+        .with_status(101)
+        .with_stderr_data(str![[r#"
+[ERROR] `cargo run` can run at most one executable, but multiple were specified
+[HELP] available targets:
+    bin `ambiguous` in package `crate1`
+    bin `ambiguous` in package `crate2`
+    bin `ambiguous` in package `crate3`
+    bin `ambiguous` in package `crate4`
+
+"#]])
+        .run();
+
+    p.cargo("run --bin crate1/ambiguous")
+        .with_status(101)
+        .with_stderr_data(str![[r#"
+[ERROR] no bin target named `crate1/ambiguous` in default-run packages
+[HELP] available bin targets:
+    ambiguous in package crate1
+    ambiguous in package crate2
+    ambiguous in package crate3
+    ambiguous in package crate4
+
+"#]])
+        .run();
+}
+
+// See rust-lang/cargo#14544
+#[cargo_test]
+fn print_available_targets_within_virtual_workspace() {
+    let p = project()
+        .file(
+            "Cargo.toml",
+            r#"
+        [workspace]
+        resolver = "3"
+        members = ["crate1", "crate2", "pattern1", "pattern2"]
+
+        default-members = ["crate1"]
+        "#,
+        )
+        .file("crate1/src/main.rs", "fn main(){}")
+        .file(
+            "crate1/Cargo.toml",
+            r#"
+        [package]
+        name = "crate1"
+        version = "0.1.0"
+        edition = "2024"
+    "#,
+        )
+        .file("crate2/src/main.rs", "fn main(){}")
+        .file(
+            "crate2/Cargo.toml",
+            r#"
+        [package]
+        name = "crate2"
+        version = "0.1.0"
+        edition = "2024"
+    "#,
+        )
+        .file("pattern1/src/main.rs", "fn main(){}")
+        .file(
+            "pattern1/Cargo.toml",
+            r#"
+        [package]
+        name = "pattern1"
+        version = "0.1.0"
+        edition = "2024"
+    "#,
+        )
+        .file("pattern2/src/main.rs", "fn main(){}")
+        .file(
+            "pattern2/Cargo.toml",
+            r#"
+        [package]
+        name = "pattern2"
+        version = "0.1.0"
+        edition = "2024"
+    "#,
+        )
+        .file("another/src/main.rs", "fn main(){}")
+        .file(
+            "another/Cargo.toml",
+            r#"
+        [package]
+        name = "another"
+        version = "0.1.0"
+        edition = "2024"
+    "#,
+        );
+
+    let p = p.build();
+    p.cargo("run --bin")
+        .with_status(101)
+        .with_stderr_data(str![[r#"
+[ERROR] "--bin" takes one argument.
+Available binaries:
+    crate1
+
+
+"#]])
+        .run();
+
+    p.cargo("run -p crate1 --bin crate2")
+        .with_status(101)
+        .with_stderr_data(str![[r#"
+[ERROR] no bin target named `crate2` in `crate1` package
+
+[HELP] a target with a similar name exists: `crate1`
+[HELP] available bin in `crate2` package:
+    crate2
+
+"#]])
+        .run();
+
+    p.cargo("check -p crate1 -p pattern1 -p pattern2 --bin crate2")
+        .with_status(101)
+        .with_stderr_data(str![[r#"
+[ERROR] no bin target named `crate2` in `crate1`, ... packages
+
+[HELP] a target with a similar name exists: `crate1`
+[HELP] available bin in `crate2` package:
+    crate2
+
+"#]])
+        .run();
+
+    p.cargo("run --bin crate2")
+        .with_status(101)
+        .with_stderr_data(str![[r#"
+[ERROR] no bin target named `crate2` in default-run packages
+
+[HELP] a target with a similar name exists: `crate1`
+[HELP] available bin in `crate2` package:
+    crate2
+
+"#]])
+        .run();
+
+    p.cargo("check --bin pattern*")
+        .with_status(101)
+        .with_stderr_data(str![[r#"
+[ERROR] no bin target matches pattern `pattern*` in default-run packages
+[HELP] available bin in `pattern1` package:
+    pattern1
+[HELP] available bin in `pattern2` package:
+    pattern2
+
+"#]])
+        .run();
+
+    // This another branch that none of similar name exists, and print available targets in the
+    // default-members.
+    p.change_file(
+        "Cargo.toml",
+        r#"
+        [workspace]
+        resolver = "3"
+        members = ["crate1", "crate2", "another"]
+
+        default-members = ["another"]
+        "#,
+    );
+
+    p.cargo("run --bin crate2")
+        .with_status(101)
+        .with_stderr_data(str![[r#"
+[ERROR] no bin target named `crate2` in default-run packages
+[HELP] available bin in `crate2` package:
+    crate2
+
+"#]])
+        .run();
+}
+
 #[cargo_test]
 fn either_name_or_example() {
     let p = project()
@@ -794,6 +1019,9 @@ fn either_name_or_example() {
         .with_status(101)
         .with_stderr_data(str![[r#"
 [ERROR] `cargo run` can run at most one executable, but multiple were specified
+[HELP] available targets:
+    bin `a` in package `foo`
+    example `b` in package `foo`
 
 "#]])
         .run();

tests/testsuite/test.rs

@@ -2447,16 +2447,14 @@ fn bad_example() {
     p.cargo("run --example foo")
         .with_status(101)
         .with_stderr_data(str![[r#"
-[ERROR] no example target named `foo` in default-run packages.
+[ERROR] no example target named `foo` in default-run packages
-
 
 "#]])
         .run();
     p.cargo("run --bin foo")
         .with_status(101)
         .with_stderr_data(str![[r#"
-[ERROR] no bin target named `foo` in default-run packages.
+[ERROR] no bin target named `foo` in default-run packages
-
 
 "#]])
         .run();

tests/testsuite/workspaces.rs

@@ -2716,152 +2716,3 @@ fn nonexistence_package_together_with_workspace() {
 "#]])
         .run();
 }
-
-// See rust-lang/cargo#14544
-#[cargo_test]
-fn print_available_targets_within_virtual_workspace() {
-    let p = project()
-        .file(
-            "Cargo.toml",
-            r#"
-        [workspace]
-        resolver = "3"
-        members = ["crate1", "crate2", "pattern1", "pattern2"]
-
-        default-members = ["crate1"]
-        "#,
-        )
-        .file("crate1/src/main.rs", "fn main(){}")
-        .file(
-            "crate1/Cargo.toml",
-            r#"
-        [package]
-        name = "crate1"
-        version = "0.1.0"
-        edition = "2024"
-    "#,
-        )
-        .file("crate2/src/main.rs", "fn main(){}")
-        .file(
-            "crate2/Cargo.toml",
-            r#"
-        [package]
-        name = "crate2"
-        version = "0.1.0"
-        edition = "2024"
-    "#,
-        )
-        .file("pattern1/src/main.rs", "fn main(){}")
-        .file(
-            "pattern1/Cargo.toml",
-            r#"
-        [package]
-        name = "pattern1"
-        version = "0.1.0"
-        edition = "2024"
-    "#,
-        )
-        .file("pattern2/src/main.rs", "fn main(){}")
-        .file(
-            "pattern2/Cargo.toml",
-            r#"
-        [package]
-        name = "pattern2"
-        version = "0.1.0"
-        edition = "2024"
-    "#,
-        )
-        .file("another/src/main.rs", "fn main(){}")
-        .file(
-            "another/Cargo.toml",
-            r#"
-        [package]
-        name = "another"
-        version = "0.1.0"
-        edition = "2024"
-    "#,
-        );
-
-    let p = p.build();
-    p.cargo("run --bin")
-        .with_status(101)
-        .with_stderr_data(str![[r#"
-[ERROR] "--bin" takes one argument.
-Available binaries:
-    crate1
-
-
-"#]])
-        .run();
-
-    p.cargo("run -p crate1 --bin crate2")
-        .with_status(101)
-        .with_stderr_data(str![[r#"
-[ERROR] no bin target named `crate2` in `crate1` package
-
-[HELP] a target with a similar name exists: `crate1`
-[HELP] Available bin in `crate2` package:
-    crate2
-
-"#]])
-        .run();
-
-    p.cargo("check -p crate1 -p pattern1 -p pattern2 --bin crate2")
-        .with_status(101)
-        .with_stderr_data(str![[r#"
-[ERROR] no bin target named `crate2` in `crate1`, ... packages
-
-[HELP] a target with a similar name exists: `crate1`
-[HELP] Available bin in `crate2` package:
-    crate2
-
-"#]])
-        .run();
-
-    p.cargo("run --bin crate2")
-        .with_status(101)
-        .with_stderr_data(str![[r#"
-[ERROR] no bin target named `crate2` in default-run packages
-
-[HELP] a target with a similar name exists: `crate1`
-[HELP] Available bin in `crate2` package:
-    crate2
-
-"#]])
-        .run();
-
-    p.cargo("check --bin pattern*")
-        .with_status(101)
-        .with_stderr_data(str![[r#"
-[ERROR] no bin target matches pattern `pattern*` in default-run packages.
-[HELP] Available bin in `pattern1` package:
-    pattern1
-[HELP] Available bin in `pattern2` package:
-    pattern2
-
-"#]])
-        .run();
-
-    // This another branch that none of similar name exists, and print available targets in the
-    // default-members.
-    p.change_file(
-        "Cargo.toml",
-        r#"
-        [workspace]
-        resolver = "3"
-        members = ["crate1", "crate2", "another"]
-
-        default-members = ["another"]
-        "#,
-    );
-
-    p.cargo("run --bin crate2")
-        .with_status(101)
-        .with_stderr_data(str![[r#"
-[ERROR] no bin target named `crate2` in default-run packages.
-[HELP] Available bin in `crate2` package:
-    crate2
-
-"#]])
-        .run();
-}