Add more error checking

src/lib.rs

@@ -61,18 +61,18 @@ impl From<JSONValue> for JSONMap {
     fn from(val: JSONValue) -> JSONMap {
         match val {
             JSONValue::Object(o) => o,
-            _ => panic!("Invalid type conversion")
+            _ => unreachable!(),
         }
     }
 }
 
-impl From<JSONValue> for JSONArray{
+impl From<JSONValue> for JSONArray {
     /// Extracts the `Vec` in the `JSONValue` enum, if it exists.
     /// Otherwise, panics.
     fn from(val: JSONValue) -> JSONArray {
         match val {
             JSONValue::Array(a) => a,
-            _ => panic!("Invalid type conversion")
+            _ => unreachable!(),
         }
     }
 }
@@ -83,7 +83,7 @@ impl From<JSONValue> for f64 {
     fn from(val: JSONValue) -> f64 {
         match val {
             JSONValue::Number(n) => n,
-            _ => panic!("Invalid type conversion")
+            _ => unreachable!(),
         }
     }
 }
@@ -94,7 +94,7 @@ impl From<JSONValue> for String {
     fn from(val: JSONValue) -> String {
         match val {
             JSONValue::String(s) => s,
-            _ => panic!("Invalid type conversion")
+            _ => unreachable!(),
         }
     }
 }
@@ -106,14 +106,16 @@ impl From<JSONValue> for bool {
         match val {
             JSONValue::True => true,
             JSONValue::False => false,
-            _ => panic!("Invalid type conversion")
+            _ => unreachable!(),
         }
     }
 }
 
 impl From<JSONValue> for () {
     /// This will just swallow the enum value and return a unit tuple
-    fn from(_: JSONValue) -> () { () }
+    fn from(_: JSONValue) -> () {
+        ()
+    }
 }
 
 impl From<JSONMap> for JSONValue {
@@ -245,7 +247,9 @@ impl JSON {
         );
 
         // Every parser failed, so the syntax is probably incorrect
-        Err(ParseError::UnexpectedEndOfInput(format!("Doesn't seem to be valid JSON")))
+        Err(ParseError::UnexpectedEndOfInput(format!(
+            "Doesn't seem to be valid JSON"
+        )))
     }
 
     /// See if there's a `JSONValue::Object` next in the JSON
@@ -270,20 +274,21 @@ impl JSON {
             if initial == false {
                 self.eat(',')?;
                 self.skip_whitespace();
+            } else {
+                self.skip_whitespace();
+            }
+
+            let maybe_key = self.parse_string()?;
+            if maybe_key.is_none() {
+                return Err(ParseError::ExpectedObjectKey(format!(
+                    "Expected an object key. Does the object have a trailing comma?"
+                )));
             }
 
-            self.skip_whitespace();
-
-            let key = match self.parse_string()? {
-                Some(value) => match value {
-                    JSONValue::String(s) => s,
-                    _ => panic!("parse_string returned non-string value"),
-                },
-                None => String::new(),
-            };
-
             self.skip_whitespace();
             self.eat(':')?;
+
+            let key = maybe_key.unwrap().into();
             let value = self.parse_value()?;
 
             result.insert(key, value);
@@ -293,6 +298,7 @@ impl JSON {
             self.skip_whitespace();
         }
 
+        self.expect_not_end('}')?;
         // Move to the next character: '}'
         self.increment(1);
 
@@ -322,6 +328,7 @@ impl JSON {
             initial = false;
         }
 
+        self.expect_not_end(']')?;
         // move to next character: ']'
         self.increment(1);
 
@@ -360,8 +367,8 @@ impl JSON {
                     };
                     result.push(ch);
                     self.increment(1);
-                } else if ch == 'u'
+                } else if ch == 'u' {
-                    && self.chars[self.i + 2].is_ascii_hexdigit()
+                    if self.chars[self.i + 2].is_ascii_hexdigit()
                         && self.chars[self.i + 3].is_ascii_hexdigit()
                         && self.chars[self.i + 4].is_ascii_hexdigit()
                         && self.chars[self.i + 5].is_ascii_hexdigit()
@@ -376,6 +383,15 @@ impl JSON {
                         result.push_str(&string);
 
                         self.increment(5);
+                    } else {
+                        return Err(ParseError::ExpectedUnicodeEscape(format!(
+                            "Expected a unicode escape sequence"
+                        )));
+                    }
+                } else {
+                    return Err(ParseError::ExpectedEscapeChar(format!(
+                        "Expected an escape sequence"
+                    )));
                 }
             } else {
                 result.push(self.chars[self.i]);
@@ -383,7 +399,8 @@ impl JSON {
             self.increment(1);
         }
 
-        self.eat('"')?;
+        self.expect_not_end('"')?;
+        self.increment(1);
 
         Ok(Some(JSONValue::from(result)))
     }
@@ -404,6 +421,7 @@ impl JSON {
         // Minus sign
         if self.chars[n] == '-' && n < max {
             n += 1;
+            self.expect_digit(start, n)?;
         }
 
         // Integer Part
@@ -414,6 +432,7 @@ impl JSON {
         // Decimal Part
         if self.chars[n] == '.' && n < max {
             n += 1;
+            self.expect_digit(start, n)?;
             while self.chars[n].is_ascii_digit() && n < max {
                 n += 1;
             }
@@ -428,6 +447,7 @@ impl JSON {
             }
 
             // Exponent base
+            self.expect_digit(start, n)?;
             while self.chars[n].is_ascii_digit() && n < max {
                 n += 1;
             }
@@ -512,6 +532,31 @@ impl JSON {
         }
     }
 
+    /// Check that the next character is a digit. If not, return ParseError.
+    fn expect_digit(&mut self, start: usize, end: usize) -> Result<(), ParseError> {
+        let current = String::from_iter(&self.chars[start..end]);
+        if !self.chars[end].is_ascii_digit() {
+            Err(ParseError::ExpectedDigit(format!(
+                "Expected a digit, received '{}' after numeric '{}'",
+                self.chars[end], current
+            )))
+        } else {
+            Ok(())
+        }
+    }
+
+    /// Verify that we are not at the end of the input string
+    fn expect_not_end(&mut self, ch: char) -> Result<(), ParseError> {
+        if self.i == self.chars.len() {
+            Err(ParseError::UnexpectedEndOfInput(format!(
+                "Unexpected end of input. Expected '{}'",
+                ch
+            )))
+        } else {
+            Ok(())
+        }
+    }
+
     /// Convert a `&str` containing JSON into a `Result<JSONValue, ParseError>`
     pub fn parse(json: &str) -> JSONResult {
         JSON::new(json).parse_value()
@@ -520,7 +565,7 @@ impl JSON {
 
 #[cfg(test)]
 mod tests {
-    use super::JSONValue::{Array, False, Null, Number, Object, True};
+    use super::JSONValue::{Array, Number, True};
     use super::*;
 
     #[test]
@@ -528,7 +573,11 @@ mod tests {
         let map: JSONMap = HashMap::new();
         let num = 9.380831539;
         let str = "applesauce";
-        let arr: JSONArray = vec![JSONValue::from(map.clone()), JSONValue::from(num), JSONValue::from(str)];
+        let arr: JSONArray = vec![
+            JSONValue::from(map.clone()),
+            JSONValue::from(num),
+            JSONValue::from(str),
+        ];
 
         assert_eq!(map.clone(), JSONMap::from(JSONValue::from(map.clone())));
         assert_eq!(num, f64::from(JSONValue::from(num)));
@@ -544,7 +593,11 @@ mod tests {
         let map: JSONMap = HashMap::new();
         let num = 9.380831539;
         let str = "applesauce";
-        let arr: JSONArray = vec![JSONValue::from(map.clone()), JSONValue::from(num), JSONValue::from(str)];
+        let arr: JSONArray = vec![
+            JSONValue::from(map.clone()),
+            JSONValue::from(num),
+            JSONValue::from(str),
+        ];
 
         let s: String = JSONValue::from(str).unwrap();
         let a: JSONArray = JSONValue::from(arr.clone()).unwrap();
@@ -597,9 +650,6 @@ mod tests {
         let res = JSON::new(r#""foo""#).parse_number();
         assert_eq!(res, Ok(None));
 
-        let res = JSON::new("3.14159").parse_number();
-        assert_eq!(res, Ok(Some(Number(3.14159f64))));
-
         let res = JSON::new("3e4").parse_number();
         assert_eq!(res, Ok(Some(Number(3e4f64))));
 
@@ -607,13 +657,6 @@ mod tests {
         assert_eq!(res, Ok(Some(Number(1.234f64))));
     }
 
-    #[test]
-    fn can_parse_array_of_keywords() {
-        let result = JSON::parse("[true,false,null]");
-
-        assert_eq!(result, Ok(Array(vec![True, False, Null])));
-    }
-
     #[test]
     fn parse_object() {
         let result = JSON::new(r#"{"foo": "bar"}"#).parse_object();
@@ -623,157 +666,4 @@ mod tests {
 
         assert_eq!(result, Ok(Some(JSONValue::Object(hash_map))));
     }
-
-    #[test]
-    fn parse_json_types() {
-        // Boolean / Null
-        let res = JSON::parse("true");
-        assert_eq!(res, Ok(True));
-        let res = JSON::parse("false");
-        assert_eq!(res, Ok(False));
-        let res = JSON::parse("null");
-        assert_eq!(res, Ok(Null));
-
-        // Number
-        let res = JSON::parse("9.38083151965");
-        assert_eq!(res, Ok(Number(9.38083151965)), "Failed to parse number");
-
-        // String
-        let res = JSON::parse(r#""/^$/""#);
-        assert_eq!(
-            res,
-            Ok(JSONValue::from("/^$/")),
-            "Failed to parse string"
-        );
-
-        // Number array
-        let res = JSON::parse("[1, 2, 3]");
-        assert_eq!(
-            res,
-            Ok(Array(vec![Number(1f64), Number(2f64), Number(3f64)]))
-        );
-
-        // Object array
-        let result = JSON::parse("[{}]");
-        assert_eq!(result, Ok(JSONValue::Array(vec![Object(HashMap::new())])));
-    }
-
-    #[test]
-    fn parse_nested_object() {
-        let res = JSON::parse(r#"{"a": {"b": []}}"#);
-        let mut outermap: JSONMap = HashMap::new();
-        let mut innermap: JSONMap = HashMap::new();
-
-        innermap.insert(String::from("b"), Array(vec![]));
-        outermap.insert(String::from("a"), Object(innermap));
-
-        let expected = Ok(Object(outermap));
-
-        assert_eq!(res, expected);
-    }
-
-    #[test]
-    fn parse_object_with_number_values() {
-        let result = JSON::parse(r#"[{ "a": 9.38083151965, "b": 4e3 }]"#);
-        let mut map: JSONMap = HashMap::new();
-        map.insert(String::from("a"), Number(9.38083151965f64));
-        map.insert(String::from("b"), Number(4e3f64));
-
-        let expected = Ok(Array(vec![Object(map)]));
-
-        assert_eq!(
-            result, expected,
-            "Failed on just number values: {:#?}",
-            result
-        );
-    }
-
-    #[test]
-    fn parse_weird_character_array() {
-        let result =
-            JSON::parse(r#"["\"", "\\", "/", "\b", "\f", "\n", "\r", "\t", "\u0001", "\uface"]"#);
-        let expected = Ok(Array(vec![
-            JSONValue::from("\""),
-            JSONValue::from("\\"),
-            JSONValue::from("/"),
-            JSONValue::from("\u{8}"),
-            JSONValue::from("\x0C"),
-            JSONValue::from("\n"),
-            JSONValue::from("\r"),
-            JSONValue::from("\t"),
-            JSONValue::from("\u{1}"),
-            JSONValue::from("\u{face}"),
-        ]));
-
-        assert_eq!(result, expected);
-    }
-
-    #[test]
-    fn parse_full_json_example() {
-        let result = JSON::parse(
-            r#"[{
-  "a": 9.38083151965,
-  "b": 4e3,
-  "c": [1, 2, 3],
-  "d": "foo",
-  "e": {
-    "f": {
-      "g": {
-        "h": null
-      }
-    }
-  },
-  "i": ["\"", "\\", "/", "\b", "\f", "\n", "\r", "\t", "\u0001", "\uface"]
-}]"#,
-        );
-
-        let mut map: JSONMap = HashMap::new();
-        let mut emap: JSONMap = HashMap::new();
-        let mut fmap: JSONMap = HashMap::new();
-        let mut gmap: JSONMap = HashMap::new();
-
-        gmap.insert(String::from("h"), Null);
-        fmap.insert(String::from("g"), Object(gmap));
-        emap.insert(String::from("f"), Object(fmap));
-
-        map.insert(String::from("a"), Number(9.38083151965f64));
-        map.insert(String::from("b"), Number(4e3f64));
-        map.insert(
-            String::from("c"),
-            Array(vec![Number(1f64), Number(2f64), Number(3f64)]),
-        );
-        map.insert(String::from("d"), JSONValue::from("foo"));
-        map.insert(String::from("e"), Object(emap));
-
-        map.insert(
-            String::from("i"),
-            Array(vec![
-                JSONValue::from("\""),
-                JSONValue::from("\\"),
-                JSONValue::from("/"),
-                JSONValue::from("\u{8}"),
-                JSONValue::from("\x0C"),
-                JSONValue::from("\n"),
-                JSONValue::from("\r"),
-                JSONValue::from("\t"),
-                JSONValue::from("\u{1}"),
-                JSONValue::from("\u{face}"),
-            ]),
-        );
-
-        assert!(result.is_ok(), format!("{:#?}", result));
-
-        let outer_array: Vec<JSONValue> = result.unwrap().unwrap();
-        let result_map: JSONMap = outer_array[0].clone().unwrap();
-
-        for (k, v) in &map {
-            assert_eq!(
-                result_map.get(k).unwrap(),
-                v,
-                "HashMap Entry Differs: {:#?}, {:#?}",
-                result_map.get(k).unwrap(),
-                v
-            );
-        }
-    }
 }