feat(table): improve pretty-printing for simple tables and lists (#478)

Author: vhyrro

src/table.rs

@@ -777,16 +777,45 @@ impl Table {
         let mut pairs = self.pairs::<Value, Value>().flatten().collect::<Vec<_>>();
         // Sort keys
         pairs.sort_by(|(a, _), (b, _)| a.sort_cmp(b));
+        let is_sequence = pairs.iter().enumerate().all(|(i, (k, _))| {
+            if let Value::Integer(n) = k {
+                *n == (i + 1) as Integer
+            } else {
+                false
+            }
+        });
         if pairs.is_empty() {
             return write!(fmt, "{{}}");
         }
         writeln!(fmt, "{{")?;
-        for (key, value) in pairs {
-            write!(fmt, "{}[", " ".repeat(ident + 2))?;
-            key.fmt_pretty(fmt, false, ident + 2, visited)?;
-            write!(fmt, "] = ")?;
-            value.fmt_pretty(fmt, true, ident + 2, visited)?;
-            writeln!(fmt, ",")?;
+        if is_sequence {
+            // Format as list
+            for (_, value) in pairs {
+                write!(fmt, "{}", " ".repeat(ident + 2))?;
+                value.fmt_pretty(fmt, true, ident + 2, visited)?;
+                writeln!(fmt, ",")?;
+            }
+        } else {
+            for (key, value) in pairs {
+                match key {
+                    Value::String(key)
+                        if key
+                            .to_string_lossy()
+                            .chars()
+                            .all(|c| matches!(c, 'a'..='z' | 'A'..='Z' | '0'..='9' | '_')) =>
+                    {
+                        write!(fmt, "{}{}", " ".repeat(ident + 2), key.to_string_lossy())?;
+                        write!(fmt, " = ")?;
+                    }
+                    _ => {
+                        write!(fmt, "{}[", " ".repeat(ident + 2))?;
+                        key.fmt_pretty(fmt, false, ident + 2, visited)?;
+                        write!(fmt, "] = ")?;
+                    }
+                }
+                value.fmt_pretty(fmt, true, ident + 2, visited)?;
+                writeln!(fmt, ",")?;
+            }
         }
         write!(fmt, "{}}}", " ".repeat(ident))
     }

tests/debug.rs

@@ -7,7 +7,7 @@ fn test_debug_format() -> Result<()> {
     // Globals
     let globals = lua.globals();
     let dump = format!("{globals:#?}");
-    assert!(dump.starts_with("{\n  [\"_G\"] = table:"));
+    assert!(dump.starts_with("{\n  _G = table:"));
 
     // TODO: Other cases
 

tests/table.rs

@@ -397,6 +397,7 @@ fn test_table_fmt() -> Result<()> {
         .load(
             r#"
         local t = {1, 2, 3, a = 5, b = { 6 }}
+        t["special-<chars>"] = 10
         t[9.2] = 9.2
         t[1.99] = 1.99
         t[true] = true
@@ -410,7 +411,7 @@ fn test_table_fmt() -> Result<()> {
     // Pretty print
     assert_eq!(
         format!("{table:#?}"),
-        "{\n  [false] = false,\n  [true] = true,\n  [1] = 1,\n  [1.99] = 1.99,\n  [2] = 2,\n  [3] = 3,\n  [9.2] = 9.2,\n  [\"a\"] = 5,\n  [\"b\"] = {\n    [1] = 6,\n  },\n}"
+        "{\n  [false] = false,\n  [true] = true,\n  [1] = 1,\n  [1.99] = 1.99,\n  [2] = 2,\n  [3] = 3,\n  [9.2] = 9.2,\n  a = 5,\n  b = {\n    6,\n  },\n  [\"special-<chars>\"] = 10,\n}"
     );
 
     Ok(())