misc: clippy: add manual_string_new

Signed-off-by: Philipp Schuster <philipp.schuster@cyberus-technology.de>
On-behalf-of: SAP philipp.schuster@sap.com

Cargo.toml

@@ -171,6 +171,7 @@ suspicious = "deny"
 
 # Individual Lints
 assertions_on_result_states = "deny"
+manual_string_new = "deny"
 semicolon_if_nothing_returned = "deny"
 undocumented_unsafe_blocks = "deny"
 uninlined_format_args = "deny"

hypervisor/src/arch/emulator/mod.rs

@@ -26,10 +26,10 @@ impl<T: Debug> Display for Exception<T> {
             self.ip,
             self.error
                 .map(|e| format!(": error {e:x}"))
-                .unwrap_or_else(|| "".to_owned()),
+                .unwrap_or_default(),
             self.payload
                 .map(|payload| format!(": payload {payload:x}"))
-                .unwrap_or_else(|| "".to_owned())
+                .unwrap_or_default()
         )
     }
 }

performance-metrics/src/main.rs

@@ -48,7 +48,7 @@ pub struct MetricsReport {
 
 impl Default for MetricsReport {
     fn default() -> Self {
-        let mut git_human_readable = "".to_string();
+        let mut git_human_readable = String::new();
         if let Ok(git_out) = Command::new("git").args(["describe", "--dirty"]).output() {
             if git_out.status.success() {
                 git_human_readable = String::from_utf8(git_out.stdout)
@@ -63,7 +63,7 @@ impl Default for MetricsReport {
             }
         }
 
-        let mut git_revision = "".to_string();
+        let mut git_revision = String::new();
         if let Ok(git_out) = Command::new("git").args(["rev-parse", "HEAD"]).output() {
             if git_out.status.success() {
                 git_revision = String::from_utf8(git_out.stdout)
@@ -78,7 +78,7 @@ impl Default for MetricsReport {
             }
         }
 
-        let mut git_commit_date = "".to_string();
+        let mut git_commit_date = String::new();
         if let Ok(git_out) = Command::new("git")
             .args(["show", "-s", "--format=%cd"])
             .output()

tests/integration.rs

@@ -1237,7 +1237,7 @@ fn test_vhost_user_net(
         if let Some(host_mac) = host_mac {
             format!(",host_mac={host_mac}")
         } else {
-            "".to_owned()
+            String::new()
         },
         if client_mode_daemon {
             "server"
@@ -1636,7 +1636,7 @@ fn _test_virtio_fs(
         if let Some(pci_segment) = pci_segment {
             format!(",pci_segment={pci_segment}")
         } else {
-            "".to_owned()
+            String::new()
         }
     );
 
@@ -1730,7 +1730,7 @@ fn _test_virtio_fs(
                 if let Some(pci_segment) = pci_segment {
                     format!(",pci_segment={pci_segment}")
                 } else {
-                    "".to_owned()
+                    String::new()
                 }
             );
 
@@ -2019,7 +2019,7 @@ fn _get_vmm_overhead(pid: u32, guest_memory_size: u32) -> HashMap<String, u32> {
     let reader = io::BufReader::new(smaps);
 
     let mut skip_map: bool = false;
-    let mut region_name: String = "".to_string();
+    let mut region_name: String = String::new();
     let mut region_maps = HashMap::new();
     for line in reader.lines() {
         let l = line.unwrap();
@@ -5977,7 +5977,7 @@ mod common_parallel {
                     if let Some(pci_segment) = pci_segment {
                         format!(",pci_segment={pci_segment}")
                     } else {
-                        "".to_owned()
+                        String::new()
                     }
                 )),
             );
@@ -6109,7 +6109,7 @@ mod common_parallel {
                         if let Some(pci_segment) = pci_segment {
                             format!(",pci_segment={pci_segment}")
                         } else {
-                            "".to_owned()
+                            String::new()
                         }
                     )
                     .as_str(),
@@ -6172,7 +6172,7 @@ mod common_parallel {
                         if let Some(pci_segment) = pci_segment {
                             format!(",pci_segment={pci_segment}")
                         } else {
-                            "".to_owned()
+                            String::new()
                         }
                     )
                     .as_str(),

vmm/src/config.rs

@@ -4681,7 +4681,7 @@ mod unit_tests {
         // Test empty string serial (should be valid)
         let mut empty_serial_config = valid_config.clone();
         empty_serial_config.disks = Some(vec![DiskConfig {
-            serial: Some("".to_string()),
+            serial: Some(String::new()),
             ..disk_fixture()
         }]);
         empty_serial_config.validate().unwrap();
@@ -4755,7 +4755,7 @@ mod unit_tests {
                 #[cfg(feature = "igvm")]
                 igvm: None,
                 #[cfg(feature = "sev_snp")]
-                host_data: Some("".to_string()),
+                host_data: Some(String::new()),
                 #[cfg(feature = "fw_cfg")]
                 fw_cfg_config: None,
             });