feat(cli): add error struct

migra-cli/src/config.rs

@@ -1,3 +1,4 @@
+use crate::error::{Error, ErrorKind};
 use crate::migration::Migration;
 use crate::path::PathBuilder;
 use serde::{Deserialize, Serialize};
@@ -118,21 +119,17 @@ impl Config {
             .build()
     }
 
-    pub fn database_connection(&self) -> String {
+    pub fn database_connection_string(&self) -> crate::error::Result<String> {
         let connection = self
             .database
             .connection
             .clone()
             .unwrap_or_else(|| String::from(DEFAULT_DATABASE_CONNECTION_ENV));
         if let Some(connection_env) = connection.strip_prefix("$") {
-            env::var(connection_env).unwrap_or_else(|_| {
-                panic!(
-                    r#"You need to provide "{}" environment variable"#,
-                    connection_env
-                )
-            })
+            env::var(connection_env)
+                .map_err(|e| Error::new(ErrorKind::MissedEnvVar(connection_env.to_string()), e))
         } else {
-            connection
+            Ok(connection)
         }
     }
 
@@ -143,11 +140,16 @@ impl Config {
     }
 
     pub fn migrations(&self) -> io::Result<Vec<Migration>> {
-        let mut entries = self
-            .migration_dir_path()
-            .read_dir()?
-            .map(|res| res.map(|e| e.path()))
-            .collect::<Result<Vec<_>, io::Error>>()?;
+        let mut entries = match self.migration_dir_path().read_dir() {
+            Err(e) if e.kind() == io::ErrorKind::NotFound => return Ok(Vec::new()),
+            entries => entries?
+                .map(|res| res.map(|e| e.path()))
+                .collect::<Result<Vec<_>, io::Error>>()?,
+        };
+
+        if entries.is_empty() {
+            return Ok(vec![]);
+        }
 
         entries.sort();
 

migra-cli/src/error.rs

@@ -0,0 +1,101 @@
+use std::error::Error as StdError;
+use std::fmt;
+use std::mem;
+use std::result;
+
+pub type Result<T> = result::Result<T, Error>;
+
+#[derive(Debug)]
+pub struct Error {
+    repr: Repr,
+}
+
+enum Repr {
+    Simple(ErrorKind),
+    Custom(Box<Custom>),
+}
+
+#[derive(Debug)]
+struct Custom {
+    kind: ErrorKind,
+    error: Box<dyn StdError + Send + Sync>,
+}
+
+#[derive(Debug, Clone)]
+pub enum ErrorKind {
+    MissedEnvVar(String),
+}
+
+impl fmt::Display for ErrorKind {
+    fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match *self {
+            ErrorKind::MissedEnvVar(ref name) => {
+                write!(fmt, r#"Missed "{}" environment variable"#, name)
+            }
+        }
+    }
+}
+
+impl PartialEq for ErrorKind {
+    fn eq(&self, other: &Self) -> bool {
+        mem::discriminant(self) == mem::discriminant(other)
+    }
+}
+
+impl From<ErrorKind> for Error {
+    #[inline]
+    fn from(kind: ErrorKind) -> Error {
+        Error {
+            repr: Repr::Simple(kind),
+        }
+    }
+}
+
+impl Error {
+    pub fn new<E>(kind: ErrorKind, error: E) -> Error
+    where
+        E: Into<Box<dyn StdError + Send + Sync>>,
+    {
+        Self::_new(kind, error.into())
+    }
+
+    fn _new(kind: ErrorKind, error: Box<dyn StdError + Send + Sync>) -> Error {
+        Error {
+            repr: Repr::Custom(Box::new(Custom { kind, error })),
+        }
+    }
+
+    pub fn kind(&self) -> &ErrorKind {
+        match &self.repr {
+            Repr::Custom(ref c) => &c.kind,
+            Repr::Simple(kind) => &kind,
+        }
+    }
+}
+
+impl fmt::Debug for Repr {
+    fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            Repr::Custom(ref c) => fmt::Debug::fmt(&c, fmt),
+            Repr::Simple(kind) => fmt.debug_tuple("Kind").field(&kind).finish(),
+        }
+    }
+}
+
+impl fmt::Display for Error {
+    fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match &self.repr {
+            Repr::Custom(ref c) => c.error.fmt(fmt),
+            Repr::Simple(kind) => write!(fmt, "{}", kind),
+        }
+    }
+}
+
+impl StdError for Error {
+    fn source(&self) -> Option<&(dyn StdError + 'static)> {
+        match self.repr {
+            Repr::Simple(..) => None,
+            Repr::Custom(ref c) => c.error.source(),
+        }
+    }
+}

migra-cli/src/main.rs

@@ -2,16 +2,20 @@
 
 mod config;
 mod database;
+mod error;
 mod migration;
 mod opts;
 mod path;
 
 use chrono::Local;
 use config::Config;
+use error::ErrorKind;
 use opts::{AppOpt, ApplyCommandOpt, Command, MakeCommandOpt, StructOpt};
 use path::PathBuilder;
 use std::fs;
 
+const EM_DASH: char = '—';
+
 fn main() -> Result<(), Box<dyn std::error::Error>> {
     let opt = AppOpt::from_args();
 
@@ -22,7 +26,8 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
         Command::Apply(ApplyCommandOpt { file_name }) => {
             let config = Config::read(opt.config)?;
 
-            let mut client = database::connect(&config.database_connection())?;
+            let database_connection_string = &config.database_connection_string()?;
+            let mut client = database::connect(database_connection_string)?;
 
             let file_path = PathBuilder::from(config.directory_path())
                 .append(file_name)
@@ -81,18 +86,31 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
         Command::List => {
             let config = Config::read(opt.config)?;
 
-            let mut client = database::connect(&config.database_connection())?;
-            let applied_migrations = database::applied_migrations(&mut client)?;
+            let applied_migrations = match config.database_connection_string() {
+                Ok(ref database_connection_string) => {
+                    let mut client = database::connect(database_connection_string)?;
+                    let applied_migrations = database::applied_migrations(&mut client)?;
 
-            println!("Applied migrations:");
-            if applied_migrations.is_empty() {
-                println!("–")
-            } else {
-                applied_migrations
-                    .iter()
-                    .rev()
-                    .for_each(|name| println!("{}", name));
-            }
+                    println!("Applied migrations:");
+                    if applied_migrations.is_empty() {
+                        println!("{}", EM_DASH);
+                    } else {
+                        applied_migrations
+                            .iter()
+                            .rev()
+                            .for_each(|name| println!("{}", name));
+                    }
+
+                    applied_migrations
+                }
+                Err(e) if *e.kind() == ErrorKind::MissedEnvVar(String::new()) => {
+                    println!("{}", e.kind());
+                    println!("No connection to database");
+
+                    Vec::new()
+                }
+                Err(e) => panic!(e),
+            };
 
             println!();
 
@@ -103,7 +121,7 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
                 .collect::<Vec<_>>();
             println!("Pending migrations:");
             if pending_migrations.is_empty() {
-                println!("–");
+                println!("{}", EM_DASH);
             } else {
                 pending_migrations.iter().for_each(|m| {
                     println!("{}", m.name());
@@ -113,7 +131,8 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
         Command::Upgrade => {
             let config = Config::read(opt.config)?;
 
-            let mut client = database::connect(&config.database_connection())?;
+            let database_connection_string = &config.database_connection_string()?;
+            let mut client = database::connect(database_connection_string)?;
 
             let applied_migrations = database::applied_migrations(&mut client)?;
 
@@ -136,7 +155,8 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
         Command::Downgrade => {
             let config = Config::read(opt.config)?;
 
-            let mut client = database::connect(&config.database_connection())?;
+            let database_connection_string = &config.database_connection_string()?;
+            let mut client = database::connect(database_connection_string)?;
 
             let applied_migrations = database::applied_migrations(&mut client)?;
             let migrations = config.migrations()?;