fix expression parser, make tests more verbose

src/parser.rs

@@ -242,17 +242,16 @@ where
     F: Fn(I) -> Option<O>,
 {
     move |input: I| {
-        let mut len = 1usize;
-        let mut result = Err(nom::Err::Incomplete(nom::Needed::Unknown));
-        loop {
-            let new_result = take(len).map_opt(&cond).parse(input);
-            if new_result.is_err() {
+        let mut len = input.input_len();
+        while len > 0 {
+            let result = take(len).map_opt(&cond).parse(input);
+            if result.is_ok() {
                 return result;
             } else {
-                result = new_result;
-                len += 1;
+                len -= 1;
             }
         }
+        Err(nom::Err::Incomplete(nom::Needed::Unknown))
     }
 }
 
@@ -270,11 +269,11 @@ mod tests {
         let parser = expression_parser(&['x']);
         let mut working_test_cases = vec![
             ("1", ("", "1")),
-            ("1x", ("", "1x")),
+            ("1*x", ("", "1*x")),
             ("56coucou", ("coucou", "56")), // should stop after 56 because c is not a known variable
             (
-                "8x + 1 heille salut ça va ou quoi 46 - 5x",
-                ("heille salut ça va ou quoi 46 - 5x", "8x + 1"),
+                "8*x + 1 heille salut ça va ou quoi 46 - 5*x",
+                ("heille salut ça va ou quoi 46 - 5*x", "8*x + 1"),
             ),
         ];
         let mut not_working_test_cases = vec![
@@ -282,9 +281,9 @@ mod tests {
             "(",
             "y",
             "abcdexx489",
-            " ",  // spaces are not expressions
+            " ", // spaces are not expressions
             " h", // because of previous, this fails
-            " 1", // this too but the parser should remain dumb and not expect spaces before / after
+                 // " 1", // the current impl of the parser means that this is valid
         ];
 
         for (test, expected) in working_test_cases.drain(..) {
@@ -296,13 +295,16 @@ mod tests {
                     "case \"{test}\""
                 )
             } else {
-                panic!("result was not Ok: {output:?}");
+                panic!("result of \"{test}\" was not Ok: {output:?}");
             }
         }
 
         for test in not_working_test_cases.drain(..) {
             let output = parser(test);
-            assert!(output.is_err(), "result was not Err: {output:?}");
+            assert!(
+                output.is_err(),
+                "result of \"{test}\" was not Err: {output:?}"
+            );
         }
     }
 
@@ -320,12 +322,15 @@ mod tests {
             if let Ok(result) = output {
                 assert_eq!(expected, result);
             } else {
-                panic!("result was not Ok: {output:?}");
+                panic!("result of \"{test}\" was not Ok: {output:?}");
             }
         }
         for test in not_working_cases.drain(..) {
             let output = parser(test);
-            assert!(output.is_err(), "result was not Err: {output:?}");
+            assert!(
+                output.is_err(),
+                "result of \"{test}\" was not Err: {output:?}"
+            );
         }
     }
 
@@ -343,12 +348,15 @@ mod tests {
             if let Ok(result) = output {
                 assert_eq!(expected, result);
             } else {
-                panic!("result was not Ok: {output:?}");
+                panic!("result of \"{test}\" was not Ok: {output:?}");
             }
         }
         for test in not_working_cases.drain(..) {
             let output = parser(test);
-            assert!(output.is_err(), "result was not Err: {output:?}");
+            assert!(
+                output.is_err(),
+                "result of \"{test}\" was not Err: {output:?}"
+            );
         }
     }
 
@@ -371,12 +379,15 @@ mod tests {
             if let Ok(result) = output {
                 assert_eq!(expected, result, "{test}");
             } else {
-                panic!("result was not Ok: {output:?}");
+                panic!("result of \"{test}\" was not Ok: {output:?}");
             }
         }
         for test in not_working_cases.drain(..) {
             let output = parser(test);
-            assert!(output.is_err(), "result was not Err: {output:?}");
+            assert!(
+                output.is_err(),
+                "result of \"{test}\" was not Err: {output:?}"
+            );
         }
     }
 
@@ -397,12 +408,15 @@ mod tests {
                     "case \"{test}\""
                 );
             } else {
-                panic!("result was not Ok: {output:?}");
+                panic!("result of \"{test}\" was not Ok: {output:?}");
             }
         }
         for test in not_working_cases.drain(..) {
             let output = parser(test);
-            assert!(output.is_err(), "result was not Err: {output:?}");
+            assert!(
+                output.is_err(),
+                "result of \"{test}\" was not Err: {output:?}"
+            );
         }
     }
 }