FEATURE: Error message improvements.

Selector path lookup errors render better.
We also include the actual file name we are parsing now.

src/ast/mod.rs

@@ -25,6 +25,8 @@ use std::convert::Into;
 use std::hash::Hash;
 use std::hash::Hasher;
 
+use std::fmt;
+
 macro_rules! enum_type_equality {
     ( $slf:ident, $r:expr, $( $l:pat ),* ) => {
         match $slf {
@@ -267,7 +269,7 @@ macro_rules! make_selector {
 /// let berry = {best = "strawberry", unique = "acai"}.best;
 /// let third = ["uno", "dos", "tres"].1;
 /// '''
-#[derive(Debug, PartialEq, Clone)]
+#[derive(PartialEq, Clone)]
 pub struct SelectorList {
     pub head: Box<Expression>,
     pub tail: Option<Vec<Token>>,
@@ -280,6 +282,24 @@ impl SelectorList {
     }
 }
 
+impl fmt::Debug for SelectorList {
+    fn fmt(&self, w: &mut fmt::Formatter) -> fmt::Result {
+        write!(w, "Selector({})", self)
+    }
+}
+
+impl fmt::Display for SelectorList {
+    fn fmt(&self, w: &mut fmt::Formatter) -> fmt::Result {
+        try!(write!(w, "{}", self.head));
+        if let Some(ref tok_vec) = self.tail {
+            for t in tok_vec.iter() {
+                try!(write!(w, ".{}", t.fragment));
+            }
+        }
+        return Ok(());
+    }
+}
+
 /// An ordered list of Name = Value pairs.
 ///
 /// This is usually used as the body of a tuple in the UCG AST.
@@ -709,6 +729,44 @@ impl Expression {
     }
 }
 
+impl fmt::Display for Expression {
+    fn fmt(&self, w: &mut fmt::Formatter) -> fmt::Result {
+        match self {
+            &Expression::Simple(ref v) => {
+                try!(write!(w, "{}", v.to_string()));
+            }
+            &Expression::Binary(_) => {
+                try!(write!(w, "<Expr>"));
+            }
+            &Expression::Compare(_) => {
+                try!(write!(w, "<Expr>"));
+            }
+            &Expression::ListOp(_) => {
+                try!(write!(w, "<Expr>"));
+            }
+            &Expression::Copy(_) => {
+                try!(write!(w, "<Copy>"));
+            }
+            &Expression::Grouped(_) => {
+                try!(write!(w, "(<Expr>)"));
+            }
+            &Expression::Format(_) => {
+                try!(write!(w, "<Format Expr>"));
+            }
+            &Expression::Call(_) => {
+                try!(write!(w, "<MacroCall>"));
+            }
+            &Expression::Macro(_) => {
+                try!(write!(w, "<Macro>"));
+            }
+            &Expression::Select(_) => {
+                try!(write!(w, "<Select>"));
+            }
+        }
+        Ok(())
+    }
+}
+
 /// Encodes a let statement in the UCG AST.
 #[derive(Debug, PartialEq)]
 pub struct LetDef {

src/build/mod.rs

@@ -540,16 +540,15 @@ impl Builder {
         next: (&Position, &str),
         fs: &Vec<(Positioned<String>, Rc<Val>)>,
     ) -> Result<(), Box<Error>> {
-        // This unwrap is safe because we already checked for
-        // Tuple in the pattern match.
         if let Some(vv) = Self::find_in_fieldlist(next.1, fs) {
             stack.push_back(vv.clone());
         } else {
             return Err(Box::new(error::Error::new(
                 format!(
                     "Unable to \
-                     match selector \
-                     path {:?} in file: {}",
+                     match element {} in selector \
+                     path [{}] in file: {}",
+                    next.1,
                     sl,
                     self.root.to_string_lossy(),
                 ),
@@ -574,8 +573,9 @@ impl Builder {
             return Err(Box::new(error::Error::new(
                 format!(
                     "Unable to \
-                     match selector \
-                     path {:?} in file: {}",
+                     match element {} in selector \
+                     path [{}] in file: {}",
+                    next.1,
                     sl,
                     self.root.to_string_lossy(),
                 ),
@@ -597,8 +597,7 @@ impl Builder {
             &Val::List(_) => {
                 stack.push_back(first.clone());
             }
-            val => {
-                eprintln!("Not a tuple or list! {:?}", val)
+            _ => {
                 // noop
             }
         }

src/error.rs

@@ -92,25 +92,29 @@ impl Error {
             _ => Self::new(msg, t, pos),
         }
     }
+
+    fn render(&self, w: &mut fmt::Formatter) -> fmt::Result {
+        try!(write!(
+            w,
+            "{}: \"{}\" at line: {} column: {}",
+            self.err_type, self.msg, self.pos.line, self.pos.column
+        ));
+        if let Some(ref cause) = self.cause {
+            try!(write!(w, "\n\tCaused By: {}", cause));
+        }
+        Ok(())
+    }
 }
 
 impl fmt::Debug for Error {
     fn fmt(&self, w: &mut fmt::Formatter) -> fmt::Result {
-        write!(
-            w,
-            "{}: \"{}\" at line: {} column: {}",
-            self.err_type, self.msg, self.pos.line, self.pos.column
-        )
+        self.render(w)
     }
 }
 
 impl fmt::Display for Error {
     fn fmt(&self, w: &mut fmt::Formatter) -> fmt::Result {
-        write!(
-            w,
-            "{}: \"{}\" at line: {} column: {}",
-            self.err_type, self.msg, self.pos.line, self.pos.column
-        )
+        self.render(w)
     }
 }
 

src/main.rs

@@ -17,6 +17,7 @@ extern crate ucglib;
 
 use std::fs::File;
 use std::io;
+use std::path::PathBuf;
 use std::process;
 use std::rc::Rc;
 
@@ -60,12 +61,13 @@ fn main() {
         let out = matches.value_of("out");
         let sym = matches.value_of("sym");
         let target = matches.value_of("target").unwrap();
-        let mut builder = build::Builder::new(std::env::current_dir().unwrap());
+        let root = PathBuf::from(file);
+        let mut builder = build::Builder::new(root);
         match ConverterRunner::new(target) {
             Ok(converter) => {
                 let result = builder.build_file(file);
                 if !result.is_ok() {
-                    eprintln!("{:?}", result.err());
+                    eprintln!("{:?}", result.err().unwrap());
                     process::exit(1);
                 }
                 let val = match sym {

src/tokenizer/mod.rs

@@ -119,6 +119,16 @@ macro_rules! do_tag_tok {
     // rewrite your macro argumets for you by adding an initial argument
     // for all their sub-macros. Which means we require this $i paramater
     // on the first macro invocation but not the rest.
+    ($i:expr, $type:expr, $tag:expr,WS) => {
+        do_parse!(
+            $i,
+            span: position!() >> frag: tag!($tag) >> alt!(whitespace | comment) >> (Token {
+                typ: $type,
+                pos: Position::from(span),
+                fragment: frag.fragment.to_string(),
+            })
+        )
+    };
     ($i:expr, $type:expr, $tag:expr) => {
         do_parse!(
             $i,
@@ -224,31 +234,31 @@ named!(fatcommatok( Span ) -> Token,
 );
 
 named!(lettok( Span ) -> Token,
-       do_tag_tok!(TokenType::BAREWORD, "let")
+       do_tag_tok!(TokenType::BAREWORD, "let", WS)
 );
 
 named!(selecttok( Span ) -> Token,
-       do_tag_tok!(TokenType::BAREWORD, "select")
+       do_tag_tok!(TokenType::BAREWORD, "select", WS)
 );
 
 named!(macrotok( Span ) -> Token,
-       do_tag_tok!(TokenType::BAREWORD, "macro")
+       do_tag_tok!(TokenType::BAREWORD, "macro", WS)
 );
 
 named!(importtok( Span ) -> Token,
-       do_tag_tok!(TokenType::BAREWORD, "import")
+       do_tag_tok!(TokenType::BAREWORD, "import", WS)
 );
 
 named!(astok( Span ) -> Token,
-       do_tag_tok!(TokenType::BAREWORD, "as")
+       do_tag_tok!(TokenType::BAREWORD, "as", WS)
 );
 
 named!(maptok( Span ) -> Token,
-       do_tag_tok!(TokenType::BAREWORD, "map")
+       do_tag_tok!(TokenType::BAREWORD, "map", WS)
 );
 
 named!(filtertok( Span ) -> Token,
-       do_tag_tok!(TokenType::BAREWORD, "filter")
+       do_tag_tok!(TokenType::BAREWORD, "filter", WS)
 );
 
 fn end_of_input(input: Span) -> nom::IResult<Span, Token> {