Do not suggest source config if nothing to vendor

src/cargo/ops/vendor.rs

@@ -32,11 +32,15 @@ pub fn vendor(ws: &Workspace<'_>, opts: &VendorOptions<'_>) -> CargoResult<()> {
     let vendor_config = sync(config, &workspaces, opts).with_context(|| "failed to sync")?;
 
     if config.shell().verbosity() != Verbosity::Quiet {
-        crate::drop_eprint!(
-            config,
-            "To use vendored sources, add this to your .cargo/config.toml for this project:\n\n"
-        );
-        crate::drop_print!(config, "{}", &toml::to_string(&vendor_config).unwrap());
+        if vendor_config.source.is_empty() {
+            crate::drop_eprintln!(config, "There is no dependency to vendor in this project.");
+        } else {
+            crate::drop_eprint!(
+                config,
+                "To use vendored sources, add this to your .cargo/config.toml for this project:\n\n"
+            );
+            crate::drop_print!(config, "{}", &toml::to_string(&vendor_config).unwrap());
+        }
     }
 
     Ok(())
@@ -75,6 +79,7 @@ fn sync(
 ) -> CargoResult<VendorConfig> {
     let canonical_destination = opts.destination.canonicalize();
     let canonical_destination = canonical_destination.as_deref().unwrap_or(opts.destination);
+    let dest_dir_already_exists = canonical_destination.exists();
 
     paths::create_dir_all(&canonical_destination)?;
     let mut to_remove = HashSet::new();
@@ -239,12 +244,6 @@ fn sync(
     let mut config = BTreeMap::new();
 
     let merged_source_name = "vendored-sources";
-    config.insert(
-        merged_source_name.to_string(),
-        VendorSource::Directory {
-            directory: opts.destination.to_path_buf(),
-        },
-    );
 
     // replace original sources with vendor
     for source_id in sources {
@@ -290,6 +289,18 @@ fn sync(
         config.insert(name, source);
     }
 
+    if !config.is_empty() {
+        config.insert(
+            merged_source_name.to_string(),
+            VendorSource::Directory {
+                directory: opts.destination.to_path_buf(),
+            },
+        );
+    } else if !dest_dir_already_exists {
+        // Nothing to vendor. Remove the destination dir we've just created.
+        paths::remove_dir(canonical_destination)?;
+    }
+
     Ok(VendorConfig { source: config })
 }
 

tests/testsuite/vendor.rs

@@ -753,3 +753,34 @@ fn vendor_preserves_permissions() {
     let metadata = fs::metadata(p.root().join("vendor/bar/example.sh")).unwrap();
     assert_eq!(metadata.mode() & 0o777, 0o755);
 }
+
+#[cargo_test]
+fn no_remote_dependency_no_vendor() {
+    let p = project()
+        .file(
+            "Cargo.toml",
+            r#"
+                [package]
+                name = "foo"
+                version = "0.1.0"
+                [dependencies]
+                bar = { path = "bar" }
+            "#,
+        )
+        .file("src/lib.rs", "")
+        .file(
+            "bar/Cargo.toml",
+            r#"
+                [package]
+                name = "bar"
+                version = "0.1.0"
+            "#,
+        )
+        .file("bar/src/lib.rs", "")
+        .build();
+
+    p.cargo("vendor")
+        .with_stderr("There is no dependency to vendor in this project.")
+        .run();
+    assert!(!p.root().join("vendor").exists());
+}