lua: make it easier to write type-safe functions

implementing the `ToLua` and `FromLua` traits allows `create_function`
to automatically apply the appropriate conversions to the parameters
and return values in a callback function.

That makes it possible (and nicer!) to write properly typed callbacks.

src/config/color.rs

@@ -2,7 +2,7 @@ use crate::config::*;
 use termwiz::cell::CellAttributes;
 use termwiz::color::{ColorSpec, RgbColor};
 
-#[derive(Debug, Deserialize, Clone)]
+#[derive(Debug, Deserialize, Serialize, Clone)]
 pub struct Palette {
     /// The text color to use when the attributes are reset to default
     pub foreground: Option<RgbColor>,
@@ -26,6 +26,7 @@ pub struct Palette {
     /// represents the current viewable area
     pub scrollbar_thumb: Option<RgbColor>,
 }
+impl_lua_conversion!(Palette);
 
 impl From<Palette> for term::color::ColorPalette {
     fn from(cfg: Palette) -> term::color::ColorPalette {
@@ -61,7 +62,7 @@ impl From<Palette> for term::color::ColorPalette {
 }
 
 /// Specify the text styling for a tab in the tab bar
-#[derive(Debug, Deserialize, Clone, Default)]
+#[derive(Debug, Deserialize, Serialize, Clone, Default)]
 pub struct TabBarColor {
     /// Specifies the intensity attribute for the tab title text
     #[serde(default)]
@@ -80,6 +81,7 @@ pub struct TabBarColor {
     /// The forgeground/text color for the tab
     pub fg_color: RgbColor,
 }
+impl_lua_conversion!(TabBarColor);
 
 impl TabBarColor {
     pub fn as_cell_attributes(&self) -> CellAttributes {
@@ -97,7 +99,7 @@ impl TabBarColor {
 /// Specifies the colors to use for the tab bar portion of the UI.
 /// These are not part of the terminal model and cannot be updated
 /// in the same way that the dynamic color schemes are.
-#[derive(Debug, Deserialize, Clone)]
+#[derive(Debug, Deserialize, Serialize, Clone)]
 pub struct TabBarColors {
     /// The background color for the tab bar
     #[serde(default = "default_background")]
@@ -115,6 +117,7 @@ pub struct TabBarColors {
     #[serde(default = "default_inactive_tab_hover")]
     pub inactive_tab_hover: TabBarColor,
 }
+impl_lua_conversion!(TabBarColors);
 
 fn default_background() -> RgbColor {
     RgbColor::new(0x0b, 0x00, 0x22)
@@ -154,8 +157,9 @@ impl Default for TabBarColors {
     }
 }
 
-#[derive(Debug, Deserialize, Clone)]
+#[derive(Debug, Deserialize, Serialize, Clone)]
 pub struct ColorSchemeFile {
     /// The color palette
     pub colors: Palette,
 }
+impl_lua_conversion!(ColorSchemeFile);

src/config/daemon.rs

@@ -2,12 +2,13 @@ use crate::config::*;
 use std::fs::{File, OpenOptions};
 use std::path::PathBuf;
 
-#[derive(Default, Debug, Clone, Deserialize)]
+#[derive(Default, Debug, Clone, Deserialize, Serialize)]
 pub struct DaemonOptions {
     pub pid_file: Option<PathBuf>,
     pub stdout: Option<PathBuf>,
     pub stderr: Option<PathBuf>,
 }
+impl_lua_conversion!(DaemonOptions);
 
 fn open_log(path: PathBuf) -> anyhow::Result<File> {
     create_user_owned_dirs(

src/config/font.rs

@@ -8,7 +8,7 @@ const FONT_FAMILY: &str = "Consolas";
 #[cfg(all(not(target_os = "macos"), not(windows)))]
 const FONT_FAMILY: &str = "monospace";
 
-#[derive(Debug, Copy, Deserialize, Clone, PartialEq, Eq, Hash)]
+#[derive(Debug, Copy, Deserialize, Serialize, Clone, PartialEq, Eq, Hash)]
 pub enum FontHinting {
     /// No hinting is performed
     None,
@@ -21,6 +21,7 @@ pub enum FontHinting {
     /// Vertical and horizontal hinting is performed.
     Full,
 }
+impl_lua_conversion!(FontHinting);
 
 impl Default for FontHinting {
     fn default() -> Self {
@@ -28,12 +29,13 @@ impl Default for FontHinting {
     }
 }
 
-#[derive(Debug, Copy, Deserialize, Clone, PartialEq, Eq, Hash)]
+#[derive(Debug, Copy, Deserialize, Serialize, Clone, PartialEq, Eq, Hash)]
 pub enum FontAntiAliasing {
     None,
     Greyscale,
     Subpixel,
 }
+impl_lua_conversion!(FontAntiAliasing);
 
 impl Default for FontAntiAliasing {
     fn default() -> Self {
@@ -52,6 +54,7 @@ pub struct FontAttributes {
     #[serde(default)]
     pub italic: bool,
 }
+impl_lua_conversion!(FontAttributes);
 
 impl FontAttributes {
     pub fn new(family: &str) -> Self {
@@ -85,6 +88,7 @@ pub struct TextStyle {
     /// the text color for eg: bold text.
     pub foreground: Option<RgbColor>,
 }
+impl_lua_conversion!(TextStyle);
 
 impl Default for TextStyle {
     fn default() -> Self {
@@ -178,7 +182,7 @@ impl TextStyle {
 /// The above is translated as: "if the `CellAttributes` have the italic bit
 /// set, then use the italic style of font rather than the default", and
 /// stop processing further font rules.
-#[derive(Debug, Default, Deserialize, Clone)]
+#[derive(Debug, Default, Deserialize, Serialize, Clone)]
 pub struct StyleRule {
     /// If present, this rule matches when CellAttributes::intensity holds
     /// a value that matches this rule.  Valid values are "Bold", "Normal",
@@ -207,3 +211,4 @@ pub struct StyleRule {
     /// When this rule matches, `font` specifies the styling to be used.
     pub font: TextStyle,
 }
+impl_lua_conversion!(StyleRule);

src/config/keys.rs

@@ -1,9 +1,9 @@
 use crate::keyassignment::{KeyAssignment, SpawnTabDomain};
 use anyhow::{anyhow, Error};
-use serde::{Deserialize, Deserializer};
+use serde::{Deserialize, Deserializer, Serialize};
 use termwiz::input::{KeyCode, Modifiers};
 
-#[derive(Debug, Deserialize, Clone)]
+#[derive(Debug, Deserialize, Serialize, Clone)]
 pub struct Key {
     #[serde(deserialize_with = "de_keycode")]
     pub key: KeyCode,
@@ -13,6 +13,7 @@ pub struct Key {
     #[serde(default)]
     pub arg: Option<String>,
 }
+impl_lua_conversion!(Key);
 
 impl std::convert::TryInto<KeyAssignment> for &Key {
     type Error = Error;
@@ -89,7 +90,7 @@ impl std::convert::TryInto<KeyAssignment> for &Key {
     }
 }
 
-#[derive(Debug, Deserialize, Clone)]
+#[derive(Debug, Deserialize, Serialize, Clone)]
 pub enum KeyAction {
     SpawnTab,
     SpawnTabInCurrentTabDomain,
@@ -116,6 +117,7 @@ pub enum KeyAction {
     ScrollByPage,
     ShowTabNavigator,
 }
+impl_lua_conversion!(KeyAction);
 
 fn de_keycode<'de, D>(deserializer: D) -> Result<KeyCode, D::Error>
 where

src/config/mod.rs

@@ -492,7 +492,7 @@ pub struct Config {
     pub use_local_build_for_proxy: bool,
 }
 
-#[derive(Deserialize, Clone, Copy, Debug)]
+#[derive(Deserialize, Serialize, Clone, Copy, Debug)]
 pub enum DefaultCursorStyle {
     BlinkingBlock,
     SteadyBlock,
@@ -501,6 +501,7 @@ pub enum DefaultCursorStyle {
     BlinkingBar,
     SteadyBar,
 }
+impl_lua_conversion!(DefaultCursorStyle);
 
 impl Default for DefaultCursorStyle {
     fn default() -> Self {
@@ -524,7 +525,7 @@ impl DefaultCursorStyle {
     }
 }
 
-#[derive(Default, Deserialize, Clone, Copy, Debug)]
+#[derive(Default, Deserialize, Serialize, Clone, Copy, Debug)]
 pub struct WindowPadding {
     #[serde(default)]
     pub left: u16,
@@ -535,6 +536,7 @@ pub struct WindowPadding {
     #[serde(default)]
     pub bottom: u16,
 }
+impl_lua_conversion!(WindowPadding);
 
 impl Default for Config {
     fn default() -> Self {

src/config/ssh.rs

@@ -1,7 +1,6 @@
 use crate::config::*;
-use serde::Deserialize;
 
-#[derive(Default, Debug, Clone, Deserialize)]
+#[derive(Default, Debug, Clone, Deserialize, Serialize)]
 pub struct SshDomain {
     /// The name of this specific domain.  Must be unique amongst
     /// all types of domain in the configuration file.
@@ -24,3 +23,4 @@ pub struct SshDomain {
     #[serde(default = "default_read_timeout")]
     pub timeout: Duration,
 }
+impl_lua_conversion!(SshDomain);

src/config/tls.rs

@@ -1,7 +1,7 @@
 use crate::config::*;
 use crate::SshParameters;
 
-#[derive(Default, Debug, Clone, Deserialize)]
+#[derive(Default, Debug, Clone, Deserialize, Serialize)]
 pub struct TlsDomainServer {
     /// The address:port combination on which the server will listen
     /// for client connections
@@ -24,8 +24,9 @@ pub struct TlsDomainServer {
     #[serde(default)]
     pub pem_root_certs: Vec<PathBuf>,
 }
+impl_lua_conversion!(TlsDomainServer);
 
-#[derive(Default, Debug, Clone, Deserialize)]
+#[derive(Default, Debug, Clone, Deserialize, Serialize)]
 pub struct TlsDomainClient {
     /// The name of this specific domain.  Must be unique amongst
     /// all types of domain in the configuration file.
@@ -80,6 +81,7 @@ pub struct TlsDomainClient {
     #[serde(default = "default_write_timeout")]
     pub write_timeout: Duration,
 }
+impl_lua_conversion!(TlsDomainClient);
 
 impl TlsDomainClient {
     pub fn ssh_parameters(&self) -> Option<anyhow::Result<SshParameters>> {

src/config/unix.rs

@@ -3,7 +3,7 @@ use std::path::PathBuf;
 
 /// Configures an instance of a multiplexer that can be communicated
 /// with via a unix domain socket
-#[derive(Default, Debug, Clone, Deserialize)]
+#[derive(Default, Debug, Clone, Deserialize, Serialize)]
 pub struct UnixDomain {
     /// The name of this specific domain.  Must be unique amongst
     /// all types of domain in the configuration file.
@@ -44,6 +44,7 @@ pub struct UnixDomain {
     #[serde(default = "default_write_timeout")]
     pub write_timeout: Duration,
 }
+impl_lua_conversion!(UnixDomain);
 
 impl UnixDomain {
     pub fn socket_path(&self) -> PathBuf {

src/frontend/mod.rs

@@ -3,7 +3,7 @@ use crate::mux::tab::Tab;
 use crate::mux::window::WindowId;
 use anyhow::{anyhow, Error};
 use downcast_rs::{impl_downcast, Downcast};
-use serde::Deserialize;
+use serde::{Deserialize, Serialize};
 use std::cell::RefCell;
 use std::rc::Rc;
 use std::sync::atomic::{AtomicBool, Ordering};
@@ -12,13 +12,14 @@ pub mod activity;
 pub mod gui;
 pub mod muxserver;
 
-#[derive(Debug, Deserialize, Clone, Copy, PartialEq, Eq)]
+#[derive(Debug, Deserialize, Serialize, Clone, Copy, PartialEq, Eq)]
 pub enum FrontEndSelection {
     OpenGL,
     Software,
     MuxServer,
     Null,
 }
+impl_lua_conversion!(FrontEndSelection);
 
 impl Default for FrontEndSelection {
     fn default() -> Self {

src/main.rs

@@ -18,6 +18,9 @@ use std::sync::Arc;
 use structopt::StructOpt;
 use tabout::{tabulate_output, Alignment, Column};
 
+// This module defines a macro, so it must be referenced before any other mods
+mod scripting;
+
 mod config;
 mod connui;
 mod frontend;
@@ -25,7 +28,6 @@ mod keyassignment;
 mod localtab;
 mod mux;
 mod ratelim;
-mod scripting;
 mod server;
 mod ssh;
 mod stats;

src/scripting/mod.rs

@@ -1,5 +1,8 @@
+#![macro_use]
+
+use crate::config::{FontAttributes, TextStyle};
 use anyhow::anyhow;
-use mlua::{Lua, Table, Value};
+use mlua::{Lua, Table};
 use std::path::Path;
 
 mod serde_lua;
@@ -7,6 +10,31 @@ mod serde_lua;
 pub use serde_lua::from_lua_value;
 pub use serde_lua::ser::to_lua_value;
 
+/// Implement lua conversion traits for a type.
+/// This implementation requires that the type implement
+/// serde Serialize and Deserialize.
+/// Why do we need these traits?  They allow `create_function` to
+/// operate in terms of our internal types rather than forcing
+/// the implementer to use generic Value parameter or return values.
+macro_rules! impl_lua_conversion {
+    ($struct:ident) => {
+        impl<'lua> mlua::ToLua<'lua> for $struct {
+            fn to_lua(self, lua: &'lua mlua::Lua) -> Result<mlua::Value<'lua>, mlua::Error> {
+                Ok(crate::scripting::to_lua_value(lua, self)?)
+            }
+        }
+
+        impl<'lua> mlua::FromLua<'lua> for $struct {
+            fn from_lua(
+                value: mlua::Value<'lua>,
+                _lua: &'lua mlua::Lua,
+            ) -> Result<Self, mlua::Error> {
+                Ok(crate::scripting::from_lua_value(value)?)
+            }
+        }
+    };
+}
+
 /// Set up a lua context for executing some code.
 /// The path to the directory containing the configuration is
 /// passed in and is used to pre-set some global values in
@@ -124,24 +152,18 @@ fn hostname<'lua>(_: &'lua Lua, _: ()) -> mlua::Result<String> {
 /// yields:
 /// `{ font = {{ family = "foo" }}, foreground="tomato"}`
 fn font<'lua>(
-    lua: &'lua Lua,
-    (family, map_defaults): (String, Option<Table<'lua>>),
-) -> mlua::Result<Value<'lua>> {
-    use crate::config::{FontAttributes, TextStyle};
-
-    let mut text_style: TextStyle = match map_defaults {
-        Some(def) => from_lua_value(Value::Table(def))?,
-        None => TextStyle::default(),
-    };
+    _lua: &'lua Lua,
+    (family, map_defaults): (String, Option<TextStyle>),
+) -> mlua::Result<TextStyle> {
+    let mut text_style = map_defaults.unwrap_or_else(TextStyle::default);
 
     text_style.font.clear();
     text_style.font.push(FontAttributes {
         family,
-        bold: false,
-        italic: false,
+        ..Default::default()
     });
 
-    Ok(to_lua_value(lua, text_style)?)
+    Ok(text_style)
 }
 
 /// Given a list of font family names in order of preference, return a
@@ -152,24 +174,18 @@ fn font<'lua>(
 /// The second optional argument is a list of other TextStyle fields,
 /// as described by the `wezterm.font` documentation.
 fn font_with_fallback<'lua>(
-    lua: &'lua Lua,
-    (fallback, map_defaults): (Vec<String>, Option<Table<'lua>>),
-) -> mlua::Result<Value<'lua>> {
-    use crate::config::{FontAttributes, TextStyle};
-
-    let mut text_style: TextStyle = match map_defaults {
-        Some(def) => from_lua_value(Value::Table(def))?,
-        None => TextStyle::default(),
-    };
+    _lua: &'lua Lua,
+    (fallback, map_defaults): (Vec<String>, Option<TextStyle>),
+) -> mlua::Result<TextStyle> {
+    let mut text_style = map_defaults.unwrap_or_else(TextStyle::default);
 
     text_style.font.clear();
     for family in fallback {
         text_style.font.push(FontAttributes {
             family,
-            bold: false,
-            italic: false,
+            ..Default::default()
         });
     }
 
-    Ok(to_lua_value(lua, text_style)?)
+    Ok(text_style)
 }