Ensure CLI still works with no config file

We can handle an empty config file just fine, but I forgot to handle
cases where there's *no* config file.

Author: sgrif

diesel_cli/src/config.rs

@@ -9,7 +9,7 @@ use toml;
 use super::{find_project_root, handle_error};
 use print_schema;
 
-#[derive(Deserialize)]
+#[derive(Deserialize, Default)]
 #[serde(deny_unknown_fields)]
 pub struct Config {
     #[serde(default)]
@@ -31,9 +31,14 @@ impl Config {
 
     pub fn read(matches: &ArgMatches) -> Result<Self, Box<Error>> {
         let path = Self::file_path(matches);
-        let mut bytes = Vec::new();
-        fs::File::open(path)?.read_to_end(&mut bytes)?;
-        toml::from_slice(&bytes).map_err(Into::into)
+
+        if path.exists() {
+            let mut bytes = Vec::new();
+            fs::File::open(path)?.read_to_end(&mut bytes)?;
+            toml::from_slice(&bytes).map_err(Into::into)
+        } else {
+            Ok(Self::default())
+        }
     }
 }
 

diesel_cli/tests/migration_run.rs

@@ -346,3 +346,31 @@ file = "src/my_schema.rs"
     );
     assert!(p.has_file("src/my_schema.rs"));
 }
+
+#[test]
+fn migrations_can_be_run_with_no_config_file() {
+    let p = project("migration_run_no_config_file")
+        .folder("migrations")
+        .build();
+    let db = database(&p.database_url());
+
+    p.command("database").arg("setup").run();
+
+    p.create_migration(
+        "12345_create_users_table",
+        "CREATE TABLE users ( id INTEGER )",
+        "DROP TABLE users",
+    );
+
+    assert!(!db.table_exists("users"));
+
+    let result = p.command("migration").arg("run").run();
+
+    assert!(result.is_success(), "Result was unsuccessful {:?}", result);
+    assert!(
+        result.stdout().contains("Running migration 12345"),
+        "Unexpected stdout {}",
+        result.stdout()
+    );
+    assert!(db.table_exists("users"));
+}