error: Make toml get of missing key a silent error, like git config

Fixes: #14

CHANGELOG.md

@@ -2,6 +2,8 @@
 
 ## Unreleased
 
+* `toml get` on a missing key no longer panics.  This gives it the same
+  behavior as `git config`: print nothing, and exit with failure. (#14)
 * Fix query parse error on empty quoted key `""`,
   as in `toml get data.toml 'foo."".bar'`. (#20)
 

src/main.rs

@@ -58,6 +58,11 @@ enum CliError {
     NotArray(),
     #[fail(display = "array index out of bounds")]
     ArrayIndexOob(),
+}
+
+/// An error that should cause a failure exit, but no message on stderr.
+#[derive(Debug, Fail)]
+enum SilentError {
     #[fail(display = "key not found: {}", key)]
     KeyNotFound { key: String },
 }
@@ -73,7 +78,12 @@ fn main() {
         } => set(&path, &query, &value_str),
     };
     result.unwrap_or_else(|err| {
-        eprintln!("toml: {}", err);
+        match err.downcast::<SilentError>() {
+            Ok(_) => {}
+            Err(err) => {
+                eprintln!("toml: {}", err);
+            }
+        }
         exit(1);
     })
 }
@@ -95,7 +105,7 @@ fn get(path: &PathBuf, query: &str, opts: &GetOpts) -> Result<(), Error> {
     }
 
     let item = walk_tpath(doc.as_item(), &tpath);
-    let item = item.ok_or(CliError::KeyNotFound { key: query.into() })?;
+    let item = item.ok_or(SilentError::KeyNotFound { key: query.into() })?;
 
     if opts.raw {
         if let Item::Value(Value::String(s)) = item {

test/test.rs

@@ -27,6 +27,16 @@ macro_rules! tomltest_get_err {
     };
 }
 
+macro_rules! tomltest_get_err_empty {
+    ($name:ident, $args:expr) => {
+        tomltest!($name, |mut t: TestCaseState| {
+            t.write_file(INPUT);
+            t.cmd.args(["get", &t.filename()]).args($args);
+            check_eq("", &t.expect_error());
+        });
+    };
+}
+
 macro_rules! tomltest_get {
     ($name:ident, $args:expr, $expected:expr) => {
         tomltest!($name, |mut t: TestCaseState| {
@@ -91,8 +101,8 @@ tomltest_get!(get_string_raw, ["--raw", "key"], "value\n");
 // TODO test `get --output-toml`
 
 tomltest_get_err!(get_invalid_query, [".bad"], "syntax error in query: .bad");
-tomltest_get_err!(get_missing, ["nosuchkey"], "key not found");
-tomltest_get_err!(get_missing_num, ["key[1]"], "key not found");
+tomltest_get_err_empty!(get_missing, ["nosuchkey"]);
+tomltest_get_err_empty!(get_missing_num, ["key[1]"]);
 
 macro_rules! tomltest_set {
     ($name:ident, $args:expr, $expected:expr) => {