From 6de25e7cc83795bbab2b5a19bf94ec4514f7ad8e Mon Sep 17 00:00:00 2001
From: Michael Sloan <mgsloan@gmail.com>
Date: Thu, 30 Jan 2020 23:35:15 -0700
Subject: [PATCH] Allow empty table keys

Quoting https://github.com/toml-lang/toml/tree/68076ffc6d9a150d48f1df964551283542ad47bc#user-content-keys

> A bare key must be non-empty, but an empty quoted key is allowed (though discouraged).

See also the discussion in https://github.com/toml-lang/toml/issues/432
---
 src/de.rs                             | 1 -
 src/ser.rs                            | 9 +++++----
 src/tokens.rs                         | 4 ----
 test-suite/tests/invalid-misc.rs      | 2 +-
 test-suite/tests/parser.rs            | 8 ++++----
 test-suite/tests/valid.rs             | 5 +++++
 test-suite/tests/valid/key-empty.json | 3 +++
 test-suite/tests/valid/key-empty.toml | 1 +
 8 files changed, 19 insertions(+), 14 deletions(-)
 create mode 100644 test-suite/tests/valid/key-empty.json
 create mode 100644 test-suite/tests/valid/key-empty.toml

diff --git a/src/de.rs b/src/de.rs
index 98b3a60..2c6e49a 100644
--- a/src/de.rs
+++ b/src/de.rs
@@ -1978,7 +1978,6 @@ impl<'a> Deserializer<'a> {
                 expected,
                 found,
             } => self.error(at, ErrorKind::Wanted { expected, found }),
-            TokenError::EmptyTableKey(at) => self.error(at, ErrorKind::EmptyTableKey),
             TokenError::MultilineStringKey(at) => self.error(at, ErrorKind::MultilineStringKey),
         }
     }
diff --git a/src/ser.rs b/src/ser.rs
index 90cfcd7..017903b 100644
--- a/src/ser.rs
+++ b/src/ser.rs
@@ -509,10 +509,11 @@ impl<'a> Serializer<'a> {
     }
 
     fn escape_key(&mut self, key: &str) -> Result<(), Error> {
-        let ok = key.chars().all(|c| match c {
-            'a'..='z' | 'A'..='Z' | '0'..='9' | '-' | '_' => true,
-            _ => false,
-        });
+        let ok = key.len() > 0
+            && key.chars().all(|c| match c {
+                'a'..='z' | 'A'..='Z' | '0'..='9' | '-' | '_' => true,
+                _ => false,
+            });
         if ok {
             write!(self.dst, "{}", key).map_err(ser::Error::custom)?;
         } else {
diff --git a/src/tokens.rs b/src/tokens.rs
index 49265fb..5553b07 100644
--- a/src/tokens.rs
+++ b/src/tokens.rs
@@ -56,7 +56,6 @@ pub enum Error {
     UnterminatedString(usize),
     NewlineInTableKey(usize),
     MultilineStringKey(usize),
-    EmptyTableKey(usize),
     Wanted {
         at: usize,
         expected: &'static str,
@@ -194,9 +193,6 @@ impl<'a> Tokenizer<'a> {
                 if multiline {
                     return Err(Error::MultilineStringKey(offset));
                 }
-                if val == "" {
-                    return Err(Error::EmptyTableKey(offset));
-                }
                 match src.find('\n') {
                     None => Ok((span, val)),
                     Some(i) => Err(Error::NewlineInTableKey(offset + i)),
diff --git a/test-suite/tests/invalid-misc.rs b/test-suite/tests/invalid-misc.rs
index cea0801..7a10192 100644
--- a/test-suite/tests/invalid-misc.rs
+++ b/test-suite/tests/invalid-misc.rs
@@ -14,7 +14,7 @@ fn bad() {
     bad!("a = 01", "invalid number at line 1 column 6");
     bad!("a = 1__1", "invalid number at line 1 column 5");
     bad!("a = 1_", "invalid number at line 1 column 5");
-    bad!("''", "empty table key found at line 1 column 1");
+    bad!("''", "expected an equals, found eof at line 1 column 3");
     bad!("a = 9e99999", "invalid number at line 1 column 5");
 
     bad!(
diff --git a/test-suite/tests/parser.rs b/test-suite/tests/parser.rs
index eab9f5a..70d418e 100644
--- a/test-suite/tests/parser.rs
+++ b/test-suite/tests/parser.rs
@@ -342,12 +342,14 @@ fn bad_keys() {
         "key|=3",
         "unexpected character found: `|` at line 1 column 4"
     );
-    bad!("\"\"=3", "empty table key found at line 1 column 1");
     bad!(
         "=3",
         "expected a table key, found an equals at line 1 column 1"
     );
-    bad!("\"\"|=3", "empty table key found at line 1 column 1");
+    bad!(
+        "\"\"|=3",
+        "unexpected character found: `|` at line 1 column 3"
+    );
     bad!("\"\n\"|=3", "newline in string found at line 1 column 2");
     bad!(
         "\"\r\"|=3",
@@ -381,12 +383,10 @@ fn bad_table_names() {
         "[.]",
         "expected a table key, found a period at line 1 column 2"
     );
-    bad!("[\"\".\"\"]", "empty table key found at line 1 column 2");
     bad!(
         "[a.]",
         "expected a table key, found a right bracket at line 1 column 4"
     );
-    bad!("[\"\"]", "empty table key found at line 1 column 2");
     bad!("[!]", "unexpected character found: `!` at line 1 column 2");
     bad!("[\"\n\"]", "newline in string found at line 1 column 3");
     bad!(
diff --git a/test-suite/tests/valid.rs b/test-suite/tests/valid.rs
index 0bb7caa..9729063 100644
--- a/test-suite/tests/valid.rs
+++ b/test-suite/tests/valid.rs
@@ -231,6 +231,11 @@ test!(
     include_str!("valid/key-with-pound.toml"),
     include_str!("valid/key-with-pound.json")
 );
+test!(
+    key_empty,
+    include_str!("valid/key-empty.toml"),
+    include_str!("valid/key-empty.json")
+);
 test!(
     long_float,
     include_str!("valid/long-float.toml"),
diff --git a/test-suite/tests/valid/key-empty.json b/test-suite/tests/valid/key-empty.json
new file mode 100644
index 0000000..99afee4
--- /dev/null
+++ b/test-suite/tests/valid/key-empty.json
@@ -0,0 +1,3 @@
+{
+  "": {"type": "integer", "value": "1"}
+}
diff --git a/test-suite/tests/valid/key-empty.toml b/test-suite/tests/valid/key-empty.toml
new file mode 100644
index 0000000..2f6a07c
--- /dev/null
+++ b/test-suite/tests/valid/key-empty.toml
@@ -0,0 +1 @@
+"" = 1