Better error handling 🌍

5 files changed, 105 insertions, 77 deletions

diff --git a/src/engine.rs b/src/engine.rs
index 2fbb830b..5a6e27b0 100644
--- a/src/engine.rs
+++ b/src/engine.rs
@@ -132,15 +132,20 @@ impl<'s> Engine<'s> {
 type TypeResult<T> = std::result::Result<T, TypesetError>;
 
 /// The error type for typesetting.
-#[derive(Debug, Clone, Eq, PartialEq)]
-pub struct TypesetError {
-    message: String,
-}
+pub enum TypesetError {}
 
 impl error::Error for TypesetError {}
 
 impl fmt::Display for TypesetError {
+    #[inline]
+    fn fmt(&self, _: &mut fmt::Formatter) -> fmt::Result {
+        Ok(())
+    }
+}
+
+impl fmt::Debug for TypesetError {
+    #[inline]
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        f.write_str(&self.message)
+        fmt::Display::fmt(self, f)
     }
 }
diff --git a/src/font.rs b/src/font.rs
index ea59bd38..40fa2102 100644
--- a/src/font.rs
+++ b/src/font.rs
@@ -5,9 +5,9 @@ use std::error;
 use std::fmt;
 use std::io::{self, Cursor, Seek, SeekFrom};
 use byteorder::{BE, ReadBytesExt, WriteBytesExt};
-use opentype::{OpenTypeReader, Outlines, TableRecord, Tag};
-use opentype::tables::{Header, MacStyleFlags, Name, NameEntry, CharMap,
-    MaximumProfile, HorizontalMetrics, Post, OS2};
+use opentype::{Error as OpentypeError, OpenTypeReader, Outlines, TableRecord, Tag};
+use opentype::tables::{Header, Name, CharMap, MaximumProfile, HorizontalMetrics, Post, OS2};
+use opentype::tables::{MacStyleFlags, NameEntry};
 use crate::doc::Size;
 
 
@@ -588,8 +588,7 @@ impl<T> TakeInvalid<T> for Option<T> {
 
 type FontResult<T> = Result<T, FontError>;
 
-/// The error type for font subsetting.
-#[derive(Debug)]
+/// The error type for font operations.
 pub enum FontError {
     /// The font file is incorrect.
     InvalidFont(String),
@@ -601,9 +600,6 @@ pub enum FontError {
     MissingCharacter(char),
     /// An I/O Error occured while reading the font program.
     Io(io::Error),
-
-    #[doc(hidden)]
-    __Extensible,
 }
 
 impl error::Error for FontError {
@@ -619,18 +615,23 @@ impl error::Error for FontError {
 impl fmt::Display for FontError {
     #[inline]
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        use FontError::*;
         match self {
-            InvalidFont(message) => write!(f, "invalid font: {}", message),
-            MissingTable(table) => write!(f, "missing table: {}", table),
-            UnsupportedTable(table) => write!(f, "unsupported table: {}", table),
-            MissingCharacter(c) => write!(f, "missing character: '{}'", c),
-            Io(err) => fmt::Display::fmt(err, f),
-            __Extensible => panic!("tried to display extensible variant"),
+            FontError::InvalidFont(message) => write!(f, "invalid font: {}", message),
+            FontError::MissingTable(table) => write!(f, "missing table: {}", table),
+            FontError::UnsupportedTable(table) => write!(f, "unsupported table: {}", table),
+            FontError::MissingCharacter(c) => write!(f, "missing character: '{}'", c),
+            FontError::Io(err) => write!(f, "io error: {}", err),
         }
     }
 }
 
+impl fmt::Debug for FontError {
+    #[inline]
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        fmt::Display::fmt(self, f)
+    }
+}
+
 impl From<io::Error> for FontError {
     #[inline]
     fn from(err: io::Error) -> FontError {
@@ -638,13 +639,12 @@ impl From<io::Error> for FontError {
     }
 }
 
-impl From<opentype::Error> for FontError {
-    fn from(err: opentype::Error) -> FontError {
-        use opentype::Error::*;
+impl From<OpentypeError> for FontError {
+    fn from(err: OpentypeError) -> FontError {
         match err {
-            InvalidFont(message) => FontError::InvalidFont(message),
-            MissingTable(tag) => FontError::MissingTable(tag.to_string()),
-            Io(err) => FontError::Io(err),
+            OpentypeError::InvalidFont(message) => FontError::InvalidFont(message),
+            OpentypeError::MissingTable(tag) => FontError::MissingTable(tag.to_string()),
+            OpentypeError::Io(err) => FontError::Io(err),
             _ => panic!("unexpected extensible variant"),
         }
     }
diff --git a/src/lib.rs b/src/lib.rs
index 29daa853..6f2aaa53 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -7,17 +7,17 @@
 //! ```
 //! use typeset::Compiler;
 //!
+//! // Minimal source code for our document.
+//! let src = "Hello World from Typeset!";
+//!
 //! // Create an output file.
 //! # /*
 //! let mut file = std::fs::File::create("hello-typeset.pdf").unwrap();
 //! # */
 //! # let mut file = std::fs::File::create("../target/typeset-hello.pdf").unwrap();
 //!
-//! // Create a compiler and export a PDF.
-//! let src = "Hello World from Typeset!";
+//! // Create a compiler and write the document into a file as a PDF.
 //! let compiler = Compiler::new();
-//!
-//! // Write the document into a file as a PDF.
 //! compiler.write_pdf(src, &mut file).unwrap();
 //! ```
 
@@ -31,7 +31,7 @@ mod utility;
 
 pub use crate::parsing::{Tokens, ParseError};
 pub use crate::engine::TypesetError;
-pub use crate::pdf::PdfWritingError;
+pub use crate::pdf::PdfError;
 
 use std::error;
 use std::fmt;
@@ -74,8 +74,8 @@ impl Compiler {
 
     /// Return the abstract syntax tree representation of the document.
     #[inline]
-    pub fn parse<'s>(&self, source: &'s str) -> Result<SyntaxTree<'s>, Error> {
-        Parser::new(self.tokenize(source)).parse().map_err(Into::into)
+    pub fn parse<'s>(&self, source: &'s str) -> Result<SyntaxTree<'s>, ParseError> {
+        Parser::new(self.tokenize(source)).parse()
     }
 
     /// Return the abstract typesetted representation of the document.
@@ -92,8 +92,7 @@ impl Compiler {
     }
 }
 
-/// The error type for compilation.
-#[derive(Debug, Clone, Eq, PartialEq)]
+/// The general error type for compilation.
 pub enum Error {
     /// An error that occured while transforming source code into
     /// an abstract syntax tree.
@@ -101,7 +100,7 @@ pub enum Error {
     /// An error that occured while typesetting into an abstract document.
     Typeset(TypesetError),
     /// An error that occured while writing the document as a _PDF_.
-    PdfWrite(PdfWritingError)
+    Pdf(PdfError),
 }
 
 impl error::Error for Error {
@@ -110,7 +109,7 @@ impl error::Error for Error {
         match self {
             Error::Parse(err) => Some(err),
             Error::Typeset(err) => Some(err),
-            Error::PdfWrite(err) => Some(err),
+            Error::Pdf(err) => Some(err),
         }
     }
 }
@@ -121,11 +120,18 @@ impl fmt::Display for Error {
         match self {
             Error::Parse(err) => write!(f, "parse error: {}", err),
             Error::Typeset(err) => write!(f, "typeset error: {}", err),
-            Error::PdfWrite(err) => write!(f, "typeset error: {}", err),
+            Error::Pdf(err) => write!(f, "pdf error: {}", err),
         }
     }
 }
 
+impl fmt::Debug for Error {
+    #[inline]
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        fmt::Display::fmt(self, f)
+    }
+}
+
 impl From<ParseError> for Error {
     #[inline]
     fn from(err: ParseError) -> Error {
@@ -140,10 +146,10 @@ impl From<TypesetError> for Error {
     }
 }
 
-impl From<PdfWritingError> for Error {
+impl From<PdfError> for Error {
     #[inline]
-    fn from(err: PdfWritingError) -> Error {
-        Error::PdfWrite(err)
+    fn from(err: PdfError) -> Error {
+        Error::Pdf(err)
     }
 }
 
diff --git a/src/parsing.rs b/src/parsing.rs
index 37c83b3f..5122597f 100644
--- a/src/parsing.rs
+++ b/src/parsing.rs
@@ -359,7 +359,6 @@ impl<'s, T> Parser<'s, T> where T: Iterator<Item = Token<'s>> {
 type ParseResult<T> = std::result::Result<T, ParseError>;
 
 /// The error type for parsing.
-#[derive(Debug, Clone, Eq, PartialEq)]
 pub struct ParseError {
     /// A message describing the error.
     message: String,
@@ -368,11 +367,18 @@ pub struct ParseError {
 impl error::Error for ParseError {}
 
 impl fmt::Display for ParseError {
+    #[inline]
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         f.write_str(&self.message)
     }
 }
 
+impl fmt::Debug for ParseError {
+    #[inline]
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        fmt::Display::fmt(self, f)
+    }
+}
 
 #[cfg(test)]
 mod token_tests {
@@ -491,12 +497,12 @@ mod parse_tests {
 
     /// Test if the source code parses into the syntax tree.
     fn test(src: &str, tree: SyntaxTree) {
-        assert_eq!(Parser::new(Tokens::new(src)).parse(), Ok(tree));
+        assert_eq!(Parser::new(Tokens::new(src)).parse().unwrap(), tree);
     }
 
     /// Test if the source parses into the error.
-    fn test_err(src: &str, err: ParseError) {
-        assert_eq!(Parser::new(Tokens::new(src)).parse(), Err(err));
+    fn test_err(src: &str, err: &str) {
+        assert_eq!(Parser::new(Tokens::new(src)).parse().unwrap_err().message, err);
     }
 
     /// Short cut macro to create a syntax tree.
@@ -577,17 +583,9 @@ mod parse_tests {
     /// Tests whether errors get reported correctly.
     #[test]
     fn parse_errors() {
-        test_err("No functions here]", ParseError {
-            message: "unexpected closing bracket".to_owned(),
-        });
-        test_err("[hello][world", ParseError {
-            message: "expected closing bracket".to_owned(),
-        });
-        test_err("[hello world", ParseError {
-            message: "expected closing bracket".to_owned(),
-        });
-        test_err("[ no-name][Why?]", ParseError {
-            message: "expected identifier".to_owned(),
-        });
+        test_err("No functions here]", "unexpected closing bracket");
+        test_err("[hello][world", "expected closing bracket");
+        test_err("[hello world", "expected closing bracket");
+        test_err("[ no-name][Why?]", "expected identifier");
     }
 }
diff --git a/src/pdf.rs b/src/pdf.rs
index 4cd78d0a..b188ab91 100644
--- a/src/pdf.rs
+++ b/src/pdf.rs
@@ -4,12 +4,12 @@ use std::collections::HashSet;
 use std::error;
 use std::fmt;
 use std::io::{self, Write};
-use pdf::{PdfWriter, Reference, Rect, Version, Trailer};
-use pdf::{DocumentCatalog, PageTree, Page, Resource, Text, Content};
-use pdf::font::{Type0Font, CMapEncoding, CIDFont, CIDFontType, CIDSystemInfo,
-    WidthRecord, FontDescriptor, FontFlags, EmbeddedFont, GlyphUnit};
+use pdf::{PdfWriter, Reference, Rect, Version, Trailer, DocumentCatalog};
+use pdf::{PageTree, Page, Resource, Text, Content};
+use pdf::font::{Type0Font, CMapEncoding, CIDFont, CIDFontType, CIDSystemInfo};
+use pdf::font::{WidthRecord, FontDescriptor, FontFlags, EmbeddedFont, GlyphUnit};
 use crate::doc::{Document, Size, Text as DocText, TextCommand as DocTextCommand};
-use crate::font::Font;
+use crate::font::{Font, FontError};
 
 
 /// Writes documents in the _PDF_ format.
@@ -279,34 +279,53 @@ impl std::ops::Deref for PdfFont {
 }
 
 /// Result type used for parsing.
-type PdfResult<T> = std::result::Result<T, PdfWritingError>;
+type PdfResult<T> = std::result::Result<T, PdfError>;
 
 /// The error type for _PDF_ creation.
-#[derive(Debug, Clone, Eq, PartialEq)]
-pub struct PdfWritingError {
-    /// A message describing the error.
-    message: String,
+pub enum PdfError {
+    /// An error occured while subsetting the font for the _PDF_.
+    Font(FontError),
+    /// An I/O Error on the underlying writable occured.
+    Io(io::Error),
 }
 
-impl error::Error for PdfWritingError {}
-
-impl From<io::Error> for PdfWritingError {
+impl error::Error for PdfError {
     #[inline]
-    fn from(err: io::Error) -> PdfWritingError {
-        PdfWritingError { message: format!("{}", err) }
+    fn source(&self) -> Option<&(dyn error::Error + 'static)> {
+        match self {
+            PdfError::Font(err) => Some(err),
+            PdfError::Io(err) => Some(err),
+        }
     }
 }
 
-impl From<crate::font::FontError> for PdfWritingError {
+impl fmt::Display for PdfError {
     #[inline]
-    fn from(err: crate::font::FontError) -> PdfWritingError {
-        PdfWritingError { message: format!("{}", err) }
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match self {
+            PdfError::Font(err) => write!(f, "font error: {}", err),
+            PdfError::Io(err) => write!(f, "io error: {}", err),
+        }
     }
 }
 
-impl fmt::Display for PdfWritingError {
+impl fmt::Debug for PdfError {
     #[inline]
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        f.write_str(&self.message)
+        fmt::Display::fmt(self, f)
+    }
+}
+
+impl From<io::Error> for PdfError {
+    #[inline]
+    fn from(err: io::Error) -> PdfError {
+        PdfError::Io(err)
+    }
+}
+
+impl From<FontError> for PdfError {
+    #[inline]
+    fn from(err: FontError) -> PdfError {
+        PdfError::Font(err)
     }
 }