feat(layout): specify only tab name in `tabs` section (#722)

Allow specifying only the tab name in the `tabs` section

- For example this is now possible:
```
tabs:
  - name: first
    parts:
      - direction: Vertical
      - direction: Vertical
  - name: second
  - name: third
```
  For that the tab section defaults the direction to
  `direction::Horizontal`

- Adds an error upon specifying a tab name inside the `parts` section
  of the tab-layout

2 files changed, 47 insertions, 69 deletions

diff --git a/zellij-utils/src/input/config.rs b/zellij-utils/src/input/config.rs
index 0339d4dce..941efa1d9 100644
--- a/zellij-utils/src/input/config.rs
+++ b/zellij-utils/src/input/config.rs
@@ -45,9 +45,8 @@ pub enum ConfigError {
     IoPath(io::Error, PathBuf),
     // Internal Deserialization Error
     FromUtf8(std::string::FromUtf8Error),
-    // Missing the tab section in the layout.
-    Layout(LayoutMissingTabSectionError),
-    LayoutPartAndTab(LayoutPartAndTabError),
+    // Naming a part in a tab is unsupported
+    LayoutNameInTab(LayoutNameInTabError),
 }
 
 impl Default for Config {
@@ -139,70 +138,32 @@ impl Config {
 
 // TODO: Split errors up into separate modules
 #[derive(Debug, Clone)]
-pub struct LayoutMissingTabSectionError;
-#[derive(Debug, Clone)]
-pub struct LayoutPartAndTabError;
-
-impl fmt::Display for LayoutMissingTabSectionError {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        write!(
-            f,
-            "MissingTabSectionError:
-There needs to be exactly one `tabs` section specified in the layout file, for example:
----
-direction: Horizontal
-parts:
-  - direction: Vertical
-  - direction: Vertical
-    tabs:
-      - direction: Vertical
-      - direction: Vertical
-  - direction: Vertical
-"
-        )
-    }
-}
-
-impl std::error::Error for LayoutMissingTabSectionError {
-    fn description(&self) -> &str {
-        "One tab must be specified per Layout."
-    }
-}
+pub struct LayoutNameInTabError;
 
-impl fmt::Display for LayoutPartAndTabError {
+impl fmt::Display for LayoutNameInTabError {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         write!(
             f,
-            "LayoutPartAndTabError:
-The `tabs` and `parts` section should not be specified on the same level in the layout file, for example:
+            "LayoutNameInTabError:
+The `parts` inside the `tabs` can't be named. For example:
 ---
-direction: Horizontal
-parts:
-  - direction: Vertical
-  - direction: Vertical
 tabs:
   - direction: Vertical
-  - direction: Vertical
-  - direction: Vertical
-
-should rather be specified as:
----
-direction: Horizontal
-parts:
-  - direction: Vertical
-  - direction: Vertical
-    tabs:
-      - direction: Vertical
+    name: main
+    parts:
       - direction: Vertical
+        name: section # <== The part section can't be named.
       - direction: Vertical
+  - direction: Vertical
+    name: test
 "
         )
     }
 }
 
-impl std::error::Error for LayoutPartAndTabError {
+impl std::error::Error for LayoutNameInTabError {
     fn description(&self) -> &str {
-        "The `tabs` and parts section should not be specified on the same level."
+        "The `parts` inside the `tabs` can't be named."
     }
 }
 
@@ -215,10 +176,7 @@ impl Display for ConfigError {
             }
             ConfigError::Serde(ref err) => write!(formatter, "Deserialization error: {}", err),
             ConfigError::FromUtf8(ref err) => write!(formatter, "FromUtf8Error: {}", err),
-            ConfigError::Layout(ref err) => {
-                write!(formatter, "There was an error in the layout file, {}", err)
-            }
-            ConfigError::LayoutPartAndTab(ref err) => {
+            ConfigError::LayoutNameInTab(ref err) => {
                 write!(formatter, "There was an error in the layout file, {}", err)
             }
         }
@@ -232,8 +190,7 @@ impl std::error::Error for ConfigError {
             ConfigError::IoPath(ref err, _) => Some(err),
             ConfigError::Serde(ref err) => Some(err),
             ConfigError::FromUtf8(ref err) => Some(err),
-            ConfigError::Layout(ref err) => Some(err),
-            ConfigError::LayoutPartAndTab(ref err) => Some(err),
+            ConfigError::LayoutNameInTab(ref err) => Some(err),
         }
     }
 }
@@ -256,15 +213,9 @@ impl From<std::string::FromUtf8Error> for ConfigError {
     }
 }
 
-impl From<LayoutMissingTabSectionError> for ConfigError {
-    fn from(err: LayoutMissingTabSectionError) -> ConfigError {
-        ConfigError::Layout(err)
-    }
-}
-
-impl From<LayoutPartAndTabError> for ConfigError {
-    fn from(err: LayoutPartAndTabError) -> ConfigError {
-        ConfigError::LayoutPartAndTab(err)
+impl From<LayoutNameInTabError> for ConfigError {
+    fn from(err: LayoutNameInTabError) -> ConfigError {
+        ConfigError::LayoutNameInTab(err)
     }
 }
 
diff --git a/zellij-utils/src/input/layout.rs b/zellij-utils/src/input/layout.rs
index 98fdb0d12..9dc8cd47b 100644
--- a/zellij-utils/src/input/layout.rs
+++ b/zellij-utils/src/input/layout.rs
@@ -9,7 +9,10 @@
 //  If plugins should be able to depend on the layout system
 //  then [`zellij-utils`] could be a proper place.
 use crate::{
-    input::{command::RunCommand, config::ConfigError},
+    input::{
+        command::RunCommand,
+        config::{ConfigError, LayoutNameInTabError},
+    },
     pane_size::{Dimension, PaneGeom},
     setup,
 };
@@ -106,7 +109,12 @@ impl LayoutFromYaml {
         let layout: Option<LayoutFromYaml> = serde_yaml::from_str(&layout)?;
 
         match layout {
-            Some(layout) => Ok(layout),
+            Some(layout) => {
+                for tab in layout.tabs.clone() {
+                    tab.check()?;
+                }
+                Ok(layout)
+            }
             None => Ok(LayoutFromYaml::default()),
         }
     }
@@ -220,6 +228,7 @@ impl LayoutTemplate {
 #[derive(Debug, Serialize, Deserialize, Clone, PartialEq)]
 #[serde(crate = "self::serde")]
 pub struct TabLayout {
+    #[serde(default)]
     pub direction: Direction,
     #[serde(default)]
     pub borderless: bool,
@@ -231,6 +240,18 @@ pub struct TabLayout {
     pub name: String,
 }
 
+impl TabLayout {
+    fn check(&self) -> Result<TabLayout, ConfigError> {
+        for part in self.parts.iter() {
+            part.check()?;
+            if !part.name.is_empty() {
+                return Err(ConfigError::LayoutNameInTab(LayoutNameInTabError));
+            }
+        }
+        Ok(self.clone())
+    }
+}
+
 impl Layout {
     pub fn total_terminal_panes(&self) -> usize {
         let mut total_panes = 0;
@@ -467,6 +488,12 @@ impl Default for LayoutFromYaml {
     }
 }
 
+impl Default for Direction {
+    fn default() -> Self {
+        Direction::Horizontal
+    }
+}
+
 // The unit test location.
 #[cfg(test)]
 #[path = "./unit/layout_test.rs"]