Improve formatting / printing of userdata and tables with __type and / or __tostring metamethods

crates/lune-std-regex/src/captures.rs

@@ -81,7 +81,7 @@ impl LuaUserData for LuaCaptures {
 
         methods.add_meta_method(LuaMetaMethod::Len, |_, this, ()| Ok(this.num_captures()));
         methods.add_meta_method(LuaMetaMethod::ToString, |_, this, ()| {
-            Ok(format!("RegexCaptures({})", this.num_captures()))
+            Ok(format!("{}", this.num_captures()))
         });
     }
 

crates/lune-std-regex/src/matches.rs

@@ -47,7 +47,7 @@ impl LuaUserData for LuaMatch {
     fn add_methods<'lua, M: LuaUserDataMethods<'lua, Self>>(methods: &mut M) {
         methods.add_meta_method(LuaMetaMethod::Len, |_, this, ()| Ok(this.range().len()));
         methods.add_meta_method(LuaMetaMethod::ToString, |_, this, ()| {
-            Ok(format!("RegexMatch({})", this.slice()))
+            Ok(this.slice().to_string())
         });
     }
 }

crates/lune-std-regex/src/regex.rs

@@ -66,7 +66,7 @@ impl LuaUserData for LuaRegex {
         );
 
         methods.add_meta_method(LuaMetaMethod::ToString, |_, this, ()| {
-            Ok(format!("Regex({})", this.inner.as_str()))
+            Ok(this.inner.as_str().to_string())
         });
     }
 

crates/lune-utils/src/fmt/value/basic.rs

@@ -1,7 +1,12 @@
 use mlua::prelude::*;
 
+use crate::fmt::ErrorComponents;
+
 use super::{
-    metamethods::{call_table_tostring_metamethod, call_userdata_tostring_metamethod},
+    metamethods::{
+        call_table_tostring_metamethod, call_userdata_tostring_metamethod,
+        get_table_type_metavalue, get_userdata_type_metavalue,
+    },
     style::{COLOR_CYAN, COLOR_GREEN, COLOR_MAGENTA, COLOR_YELLOW},
 };
 
@@ -56,19 +61,39 @@ pub(crate) fn format_value_styled(value: &LuaValue, prefer_plain: bool) -> Strin
         LuaValue::Function(_) => COLOR_MAGENTA.apply_to("<function>").to_string(),
         LuaValue::LightUserData(_) => COLOR_MAGENTA.apply_to("<pointer>").to_string(),
         LuaValue::UserData(u) => {
-            if let Some(s) = call_userdata_tostring_metamethod(u) {
-                s
-            } else {
-                COLOR_MAGENTA.apply_to("<userdata>").to_string()
-            }
+            let formatted = format_typename_and_tostringed(
+                "userdata",
+                get_userdata_type_metavalue(u),
+                call_userdata_tostring_metamethod(u),
+            );
+            COLOR_MAGENTA.apply_to(formatted).to_string()
         }
         LuaValue::Table(t) => {
-            if let Some(s) = call_table_tostring_metamethod(t) {
-                s
-            } else {
-                COLOR_MAGENTA.apply_to("<table>").to_string()
-            }
+            let formatted = format_typename_and_tostringed(
+                "table",
+                get_table_type_metavalue(t),
+                call_table_tostring_metamethod(t),
+            );
+            COLOR_MAGENTA.apply_to(formatted).to_string()
         }
-        _ => COLOR_MAGENTA.apply_to("<?>").to_string(),
+        LuaValue::Error(e) => COLOR_MAGENTA
+            .apply_to(format!(
+                "<LuaError(\n{})>",
+                ErrorComponents::from(e.clone())
+            ))
+            .to_string(),
+    }
+}
+
+fn format_typename_and_tostringed(
+    fallback: &'static str,
+    typename: Option<String>,
+    tostringed: Option<String>,
+) -> String {
+    match (typename, tostringed) {
+        (Some(typename), Some(tostringed)) => format!("<{typename}({tostringed})>"),
+        (Some(typename), None) => format!("<{typename}>"),
+        (None, Some(tostringed)) => format!("<{tostringed}>"),
+        (None, None) => format!("<{fallback}>"),
     }
 }

crates/lune-utils/src/fmt/value/metamethods.rs

@@ -1,29 +1,37 @@
 use mlua::prelude::*;
 
+pub fn get_table_type_metavalue<'a>(tab: &'a LuaTable<'a>) -> Option<String> {
+    let s = tab
+        .get_metatable()?
+        .get::<_, LuaString>(LuaMetaMethod::Type.name())
+        .ok()?;
+    let s = s.to_str().ok()?;
+    Some(s.to_string())
+}
+
+pub fn get_userdata_type_metavalue<'a>(tab: &'a LuaAnyUserData<'a>) -> Option<String> {
+    let s = tab
+        .get_metatable()
+        .ok()?
+        .get::<LuaString>(LuaMetaMethod::Type.name())
+        .ok()?;
+    let s = s.to_str().ok()?;
+    Some(s.to_string())
+}
+
 pub fn call_table_tostring_metamethod<'a>(tab: &'a LuaTable<'a>) -> Option<String> {
-    let f = match tab.get_metatable() {
-        None => None,
-        Some(meta) => match meta.get::<_, LuaFunction>(LuaMetaMethod::ToString.name()) {
-            Ok(method) => Some(method),
-            Err(_) => None,
-        },
-    }?;
-    match f.call::<_, String>(()) {
-        Ok(res) => Some(res),
-        Err(_) => None,
-    }
+    tab.get_metatable()?
+        .get::<_, LuaFunction>(LuaMetaMethod::ToString.name())
+        .ok()?
+        .call(tab)
+        .ok()
 }
 
 pub fn call_userdata_tostring_metamethod<'a>(tab: &'a LuaAnyUserData<'a>) -> Option<String> {
-    let f = match tab.get_metatable() {
-        Err(_) => None,
-        Ok(meta) => match meta.get::<LuaFunction>(LuaMetaMethod::ToString.name()) {
-            Ok(method) => Some(method),
-            Err(_) => None,
-        },
-    }?;
-    match f.call::<_, String>(()) {
-        Ok(res) => Some(res),
-        Err(_) => None,
-    }
+    tab.get_metatable()
+        .ok()?
+        .get::<LuaFunction>(LuaMetaMethod::ToString.name())
+        .ok()?
+        .call(tab)
+        .ok()
 }

tests/regex/metamethods.luau

@@ -3,14 +3,14 @@
 local regex = require("@lune/regex")
 
 local re = regex.new("[0-9]+")
-assert(tostring(re) == "Regex([0-9]+)")
+assert(tostring(re) == "[0-9]+")
 assert(typeof(re) == "Regex")
 
 local mtch = re:find("1337 wow")
-assert(tostring(mtch) == "RegexMatch(1337)")
+assert(tostring(mtch) == "1337")
 assert(typeof(mtch) == "RegexMatch")
 
 local re2 = regex.new("([0-9]+) ([0-9]+) wow! ([0-9]+) ([0-9]+)")
 local captures = re2:captures("1337 125600 wow! 1984 0")
-assert(tostring(captures) == "RegexCaptures(4)")
+assert(tostring(captures) == "4")
 assert(typeof(captures) == "RegexCaptures")

tests/stdio/format.luau

@@ -1,4 +1,5 @@
 local process = require("@lune/process")
+local regex = require("@lune/regex")
 local roblox = require("@lune/roblox")
 local stdio = require("@lune/stdio")
 
@@ -9,6 +10,13 @@ local function assertFormatting(errorMessage: string, formatted: string, expecte
 	end
 end
 
+local function assertContains(errorMessage: string, haystack: string, needle: string)
+	if string.find(haystack, needle) == nil then
+		stdio.ewrite(string.format("%s\nHaystack: %s\nNeedle: %s", errorMessage, needle, haystack))
+		process.exit(1)
+	end
+end
+
 assertFormatting(
 	"Should add a single space between arguments",
 	stdio.format("Hello", "world", "!"),
@@ -47,25 +55,38 @@ assertFormatting(
 
 local userdatas = {
 	Foo = newproxy(false),
-	Bar = (roblox :: any).Vector3.new(),
+	Bar = regex.new("TEST"),
+	Baz = (roblox :: any).Vector3.new(1, 2, 3),
 }
 
 assertFormatting(
-	"Should format userdatas as their type (unknown userdata)",
+	"Should format userdatas as generic 'userdata' if unknown",
 	stdio.format(userdatas.Foo),
 	"<userdata>"
 )
 
-assertFormatting(
-	"Should format userdatas as their type (known userdata)",
+assertContains(
+	"Should format userdatas with their type if they have a __type metafield",
 	stdio.format(userdatas.Bar),
-	"<Vector3>"
+	"Regex"
+)
+
+assertContains(
+	"Should format userdatas with their type even if they have a __tostring metamethod",
+	stdio.format(userdatas.Baz),
+	"Vector3"
+)
+
+assertContains(
+	"Should format userdatas with their tostringed value if they have a __tostring metamethod",
+	stdio.format(userdatas.Baz),
+	"1, 2, 3"
 )
 
 assertFormatting(
-	"Should format userdatas as their type in tables",
+	"Should format userdatas properly in tables",
 	stdio.format(userdatas),
-	"{\n    Foo = <userdata>,\n    Bar = <Vector3>,\n}"
+	"{\n    Bar = <Regex(TEST)>,\n    Baz = <Vector3(1, 2, 3)>,\n    Foo = <userdata>,\n}"
 )
 
 local nested = {
@@ -80,7 +101,24 @@ local nested = {
 	},
 }
 
-assert(
-	string.find(stdio.format(nested), "Nesting = { ... }", 1, true) ~= nil,
-	"Should print 4 levels of nested tables before cutting off"
+assertContains(
+	"Should print 4 levels of nested tables before cutting off",
+	stdio.format(nested),
+	"Nesting = { ... }"
 )
+
+local _, errorMessage = pcall(function()
+	local function innerInnerFn()
+		process.spawn("PROGRAM_THAT_DOES_NOT_EXIST")
+	end
+	local function innerFn()
+		innerInnerFn()
+	end
+	innerFn()
+end)
+
+stdio.ewrite(typeof(errorMessage))
+
+assertContains("Should format errors similarly to userdata", stdio.format(errorMessage), "<LuaErr")
+assertContains("Should format errors with stack begins", stdio.format(errorMessage), "Stack Begin")
+assertContains("Should format errors with stack ends", stdio.format(errorMessage), "Stack End")