fix: handling of empty str for license template path (#3804)

src/config/config_type.rs

@@ -293,10 +293,12 @@ fn set_heuristics(&mut self) {
             fn set_license_template(&mut self) {
                 if self.was_set().license_template_path() {
                     let lt_path = self.license_template_path();
-                    match license::load_and_compile_template(&lt_path) {
-                        Ok(re) => self.license_template = Some(re),
-                        Err(msg) => eprintln!("Warning for license template file {:?}: {}",
-                                              lt_path, msg),
+                    if lt_path.len() > 0 {
+                        match license::load_and_compile_template(&lt_path) {
+                            Ok(re) => self.license_template = Some(re),
+                            Err(msg) => eprintln!("Warning for license template file {:?}: {}",
+                                                lt_path, msg),
+                        }
                     }
                 }
             }

src/config/mod.rs

@@ -467,6 +467,20 @@ fn test_print_docs_include_unstable() {
         assert_eq!(s.contains("(unstable)"), true);
     }
 
+    #[test]
+    fn test_empty_string_license_template_path() {
+        let toml = r#"license_template_path = """#;
+        let config = Config::from_toml(toml, Path::new("")).unwrap();
+        assert!(config.license_template.is_none());
+    }
+
+    #[test]
+    fn test_valid_license_template_path() {
+        let toml = r#"license_template_path = "tests/license-template/lt.txt""#;
+        let config = Config::from_toml(toml, Path::new("")).unwrap();
+        assert!(config.license_template.is_some());
+    }
+
     #[test]
     fn test_dump_default_config() {
         let default_config = format!(

tests/config/issue-3802.toml

@@ -0,0 +1,2 @@
+unstable_features = true
+license_template_path = ""

tests/license-template/lt.txt

@@ -0,0 +1,2 @@
+// rustfmt-license_template_path: tests/license-template/lt.txt
+// Copyright {\d+} The rustfmt developers.

tests/source/license-templates/empty_license_path.rs

@@ -0,0 +1,5 @@
+// rustfmt-config: issue-3802.toml
+
+fn main() {
+println!("Hello world!");
+}

tests/source/license-templates/license.rs

@@ -0,0 +1,6 @@
+// rustfmt-license_template_path: tests/license-template/lt.txt
+// Copyright 2019 The rustfmt developers.
+
+fn main() {
+println!("Hello world!");
+}

tests/target/license-templates/empty_license_path.rs

@@ -0,0 +1,5 @@
+// rustfmt-config: issue-3802.toml
+
+fn main() {
+    println!("Hello world!");
+}

tests/target/license-templates/license.rs

@@ -0,0 +1,6 @@
+// rustfmt-license_template_path: tests/license-template/lt.txt
+// Copyright 2019 The rustfmt developers.
+
+fn main() {
+    println!("Hello world!");
+}