spans: get rid of code duplication by introducing Span trait

2 files changed, 105 insertions, 325 deletions

diff --git a/src/emitter.rs b/src/emitter.rs
index fe98c43..e872b1f 100644
--- a/src/emitter.rs
+++ b/src/emitter.rs
@@ -5,6 +5,7 @@ use std::collections::VecDeque;
 use std::marker::PhantomData;
 use std::mem;
 
+use crate::spans::Span;
 use crate::Error;
 use crate::State;
 
@@ -189,6 +190,7 @@ pub struct DefaultEmitter<R, S> {
     seen_attributes: BTreeSet<String>,
     emitted_tokens: VecDeque<Token<S>>,
     reader: PhantomData<R>,
+    attr_in_end_tag_span: Option<S>,
 }
 
 impl<R, S> Default for DefaultEmitter<R, S> {
@@ -201,12 +203,13 @@ impl<R, S> Default for DefaultEmitter<R, S> {
             seen_attributes: BTreeSet::new(),
             emitted_tokens: VecDeque::new(),
             reader: PhantomData::default(),
+            attr_in_end_tag_span: None,
         }
     }
 }
 
-impl<R> DefaultEmitter<R, ()> {
-    fn emit_token(&mut self, token: Token<()>) {
+impl<R, S: Span<R>> DefaultEmitter<R, S> {
+    fn emit_token(&mut self, token: Token<S>) {
         self.flush_current_characters();
         self.emitted_tokens.push_front(token);
     }
@@ -219,12 +222,13 @@ impl<R> DefaultEmitter<R, ()> {
                         vacant.insert(v);
                     }
                     Entry::Occupied(_) => {
-                        self.push_error(Error::DuplicateAttribute);
+                        self.push_error(Error::DuplicateAttribute, v.name_span);
                     }
                 },
                 Some(Token::EndTag(_)) => {
+                    self.attr_in_end_tag_span = Some(v.name_span.clone());
                     if !self.seen_attributes.insert(k) {
-                        self.push_error(Error::DuplicateAttribute);
+                        self.push_error(Error::DuplicateAttribute, v.name_span);
                     }
                 }
                 _ => {
@@ -243,16 +247,15 @@ impl<R> DefaultEmitter<R, ()> {
         self.emit_token(Token::String(s));
     }
 
-    fn push_error(&mut self, error: Error) {
+    fn push_error(&mut self, error: Error, span: S) {
         // bypass character flushing in self.emit_token: we don't need the error location to be
         // that exact
-        self.emitted_tokens
-            .push_front(Token::Error { error, span: () });
+        self.emitted_tokens.push_front(Token::Error { error, span });
     }
 }
 
-impl<R> Emitter<R> for DefaultEmitter<R, ()> {
-    type Token = Token<()>;
+impl<R, S: Span<R>> Emitter<R> for DefaultEmitter<R, S> {
+    type Token = Token<S>;
 
     fn set_last_start_tag(&mut self, last_start_tag: Option<&str>) {
         self.last_start_tag.clear();
@@ -264,8 +267,8 @@ impl<R> Emitter<R> for DefaultEmitter<R, ()> {
         self.flush_current_characters();
     }
 
-    fn emit_error(&mut self, error: Error, _reader: &R) {
-        self.push_error(error);
+    fn emit_error(&mut self, error: Error, reader: &R) {
+        self.push_error(error, S::from_reader(reader));
     }
 
     fn pop_token(&mut self) -> Option<Self::Token> {
@@ -276,11 +279,17 @@ impl<R> Emitter<R> for DefaultEmitter<R, ()> {
         self.current_characters.push_str(s);
     }
 
-    fn init_start_tag(&mut self, _reader: &R) {
-        self.current_token = Some(Token::StartTag(Default::default()));
+    fn init_start_tag(&mut self, reader: &R) {
+        self.current_token = Some(Token::StartTag(StartTag {
+            name_span: S::from_reader(reader),
+            ..Default::default()
+        }));
     }
-    fn init_end_tag(&mut self, _reader: &R) {
-        self.current_token = Some(Token::EndTag(Default::default()));
+    fn init_end_tag(&mut self, reader: &R) {
+        self.current_token = Some(Token::EndTag(EndTag {
+            name_span: S::from_reader(reader),
+            ..Default::default()
+        }));
         self.seen_attributes.clear();
     }
 
@@ -293,7 +302,8 @@ impl<R> Emitter<R> for DefaultEmitter<R, ()> {
         match token {
             Token::EndTag(_) => {
                 if !self.seen_attributes.is_empty() {
-                    self.push_error(Error::EndTagWithAttributes);
+                    let span = self.attr_in_end_tag_span.take().unwrap();
+                    self.push_error(Error::EndTagWithAttributes, span);
                 }
                 self.seen_attributes.clear();
             }
@@ -316,7 +326,7 @@ impl<R> Emitter<R> for DefaultEmitter<R, ()> {
         self.emit_token(doctype);
     }
 
-    fn set_self_closing(&mut self, _reader: &R) {
+    fn set_self_closing(&mut self, reader: &R) {
         let tag = self.current_token.as_mut().unwrap();
         match tag {
             Token::StartTag(StartTag {
@@ -326,7 +336,7 @@ impl<R> Emitter<R> for DefaultEmitter<R, ()> {
                 *self_closing = true;
             }
             Token::EndTag(_) => {
-                self.push_error(Error::EndTagWithTrailingSolidus);
+                self.emit_error(Error::EndTagWithTrailingSolidus, reader);
             }
             _ => {
                 debug_assert!(false);
@@ -341,11 +351,21 @@ impl<R> Emitter<R> for DefaultEmitter<R, ()> {
     }
     fn push_tag_name(&mut self, s: &str) {
         match self.current_token {
-            Some(Token::StartTag(StartTag { ref mut name, .. })) => {
+            Some(Token::StartTag(StartTag {
+                ref mut name,
+                ref mut name_span,
+                ..
+            })) => {
                 name.push_str(s);
+                name_span.push_str(s);
             }
-            Some(Token::EndTag(EndTag { ref mut name, .. })) => {
+            Some(Token::EndTag(EndTag {
+                ref mut name,
+                ref mut name_span,
+                ..
+            })) => {
                 name.push_str(s);
+                name_span.push_str(s);
             }
             _ => debug_assert!(false),
         }
@@ -373,15 +393,30 @@ impl<R> Emitter<R> for DefaultEmitter<R, ()> {
         }));
     }
 
-    fn init_attribute_name(&mut self, _reader: &R) {
+    fn init_attribute_name(&mut self, reader: &R) {
         self.flush_current_attribute();
-        self.current_attribute = Some((String::new(), Attribute::default()));
+        self.current_attribute = Some((
+            String::new(),
+            Attribute {
+                name_span: S::from_reader(reader),
+                ..Default::default()
+            },
+        ));
+    }
+    fn init_attribute_value(&mut self, reader: &R, quoted: bool) {
+        self.current_attribute.as_mut().unwrap().1.value_span =
+            S::from_reader_with_offset(reader, quoted as usize);
     }
+
     fn push_attribute_name(&mut self, s: &str) {
-        self.current_attribute.as_mut().unwrap().0.push_str(s);
+        let current_attr = self.current_attribute.as_mut().unwrap();
+        current_attr.0.push_str(s);
+        current_attr.1.name_span.push_str(s);
     }
     fn push_attribute_value(&mut self, s: &str) {
-        self.current_attribute.as_mut().unwrap().1.value.push_str(s);
+        let current_attr = self.current_attribute.as_mut().unwrap();
+        current_attr.1.value.push_str(s);
+        current_attr.1.value_span.push_str(s);
     }
     fn set_doctype_public_identifier(&mut self, value: &str) {
         if let Some(Token::Doctype(Doctype {
diff --git a/src/spans.rs b/src/spans.rs
index c582457..88d5eed 100644
--- a/src/spans.rs
+++ b/src/spans.rs
@@ -1,13 +1,18 @@
 //! Source code spans.
-use std::{
-    collections::{btree_map::Entry, BTreeSet, VecDeque},
-    marker::PhantomData,
-    mem,
-};
+//!
+//! The [`DefaultEmitter`](crate::DefaultEmitter) is generic over a [`Span`].
+//! This library comes with two Span implementations:
+//!
+//! * one for `()` which acts as the no-op implementation for when you don't want to track spans
+//! * one for [`Range<usize>`] for when you do want to track spans
+//!
+//! To use the latter your reader however has to implement [`GetPos`].
+//! You can easily use any existing reader by wrapping it in the [`PosTracker`] struct
+//! which implements the [`GetPos`] trait and takes care of tracking the current position.
 
-use crate::{Attribute, Doctype, Emitter, EndTag, Error, Reader, StartTag, Token};
+use std::ops::Range;
 
-type Span = std::ops::Range<usize>;
+use crate::Reader;
 
 /// A trait to be implemented by readers that track their own position.
 pub trait GetPos {
@@ -29,320 +34,60 @@ impl<R> GetPos for PosTracker<R> {
     }
 }
 
-impl<R: Reader> Reader for PosTracker<R> {
-    type Error = R::Error;
-
-    fn read_char(&mut self) -> Result<Option<char>, Self::Error> {
-        match self.reader.read_char()? {
-            Some(char) => {
-                self.position += char.len_utf8();
-                Ok(Some(char))
-            }
-            None => Ok(None),
-        }
-    }
+/// Represents a character range in the source code.
+pub trait Span<R>: Default + Clone {
+    /// Initializes a new span at the current position of the reader.
+    fn from_reader(reader: &R) -> Self;
 
-    fn try_read_string(&mut self, s: &str, case_sensitive: bool) -> Result<bool, Self::Error> {
-        match self.reader.try_read_string(s, case_sensitive)? {
-            true => {
-                self.position += s.len();
-                Ok(true)
-            }
-            false => Ok(false),
-        }
-    }
-}
-
-/// The default implementation of [`crate::Emitter`], used to produce ("emit") tokens.
-pub struct SpanEmitter<R> {
-    current_characters: String,
-    current_token: Option<Token<Span>>,
-    last_start_tag: String,
-    current_attribute: Option<(String, Attribute<Span>)>,
-    seen_attributes: BTreeSet<String>,
-    emitted_tokens: VecDeque<Token<Span>>,
-    reader: PhantomData<R>,
-    attr_in_end_tag_span: Option<Span>,
-}
+    /// Initializes a new span at the current position of the reader with the given offset.
+    fn from_reader_with_offset(reader: &R, offset: usize) -> Self;
 
-impl<R> Default for SpanEmitter<R> {
-    fn default() -> Self {
-        SpanEmitter {
-            current_characters: String::new(),
-            current_token: None,
-            last_start_tag: String::new(),
-            current_attribute: None,
-            seen_attributes: BTreeSet::new(),
-            emitted_tokens: VecDeque::new(),
-            reader: PhantomData::default(),
-            attr_in_end_tag_span: None,
-        }
-    }
+    /// Extends the span by the length of the given string.
+    fn push_str(&mut self, str: &str);
 }
 
-impl<R: GetPos> SpanEmitter<R> {
-    fn emit_token(&mut self, token: Token<Span>) {
-        self.flush_current_characters();
-        self.emitted_tokens.push_front(token);
-    }
-
-    fn flush_current_attribute(&mut self) {
-        if let Some((k, v)) = self.current_attribute.take() {
-            match self.current_token {
-                Some(Token::StartTag(ref mut tag)) => match tag.attributes.entry(k) {
-                    Entry::Vacant(vacant) => {
-                        vacant.insert(v);
-                    }
-                    Entry::Occupied(_) => {
-                        self.emit_error_span(Error::DuplicateAttribute, v.name_span);
-                    }
-                },
-                Some(Token::EndTag(_)) => {
-                    self.attr_in_end_tag_span = Some(v.name_span.clone());
-                    if !self.seen_attributes.insert(k) {
-                        self.emit_error_span(Error::DuplicateAttribute, v.name_span);
-                    }
-                }
-                _ => {
-                    debug_assert!(false);
-                }
-            }
-        }
-    }
-
-    fn flush_current_characters(&mut self) {
-        if self.current_characters.is_empty() {
-            return;
-        }
+impl<R> Span<R> for () {
+    fn from_reader(_reader: &R) -> Self {}
 
-        let s = mem::take(&mut self.current_characters);
-        self.emit_token(Token::String(s));
-    }
+    fn from_reader_with_offset(_reader: &R, _offset: usize) -> Self {}
 
-    fn emit_error_span(&mut self, error: Error, span: Span) {
-        // bypass character flushing in self.emit_token: we don't need the error location to be
-        // that exact
-        self.emitted_tokens.push_front(Token::Error { error, span });
-    }
+    fn push_str(&mut self, _str: &str) {}
 }
 
-impl<R: GetPos> Emitter<R> for SpanEmitter<R> {
-    type Token = Token<Span>;
-
-    fn set_last_start_tag(&mut self, last_start_tag: Option<&str>) {
-        self.last_start_tag.clear();
-        self.last_start_tag
-            .push_str(last_start_tag.unwrap_or_default());
+impl<P: GetPos> Span<P> for Range<usize> {
+    fn from_reader(reader: &P) -> Self {
+        reader.get_pos() - 1..reader.get_pos() - 1
     }
 
-    fn emit_eof(&mut self) {
-        self.flush_current_characters();
+    fn from_reader_with_offset(reader: &P, offset: usize) -> Self {
+        reader.get_pos() - 1 + offset..reader.get_pos() - 1 + offset
     }
 
-    fn emit_error(&mut self, error: Error, reader: &R) {
-        self.emit_error_span(error, reader.get_pos() - 1..reader.get_pos() - 1)
-    }
-
-    fn pop_token(&mut self) -> Option<Self::Token> {
-        self.emitted_tokens.pop_back()
-    }
-
-    fn emit_string(&mut self, s: &str) {
-        self.current_characters.push_str(s);
-    }
-
-    fn init_start_tag(&mut self, reader: &R) {
-        self.current_token = Some(Token::StartTag(StartTag {
-            name_span: reader.get_pos() - 1..reader.get_pos() - 1,
-            ..Default::default()
-        }));
-    }
-    fn init_end_tag(&mut self, reader: &R) {
-        self.current_token = Some(Token::EndTag(EndTag {
-            name_span: reader.get_pos() - 1..reader.get_pos() - 1,
-            ..Default::default()
-        }));
-        self.seen_attributes.clear();
-    }
-
-    fn init_comment(&mut self, _reader: &R) {
-        self.current_token = Some(Token::Comment(String::new()));
-    }
-    fn emit_current_tag(&mut self) {
-        self.flush_current_attribute();
-        let mut token = self.current_token.take().unwrap();
-        match token {
-            Token::EndTag(_) => {
-                if !self.seen_attributes.is_empty() {
-                    let span = self.attr_in_end_tag_span.take().unwrap();
-                    self.emit_error_span(Error::EndTagWithAttributes, span);
-                }
-                self.seen_attributes.clear();
-            }
-            Token::StartTag(ref mut _tag) => {
-                self.set_last_start_tag(Some(&_tag.name));
-            }
-            _ => debug_assert!(false),
-        }
-        self.emit_token(token);
-    }
-    fn emit_current_comment(&mut self) {
-        let comment = self.current_token.take().unwrap();
-        debug_assert!(matches!(comment, Token::Comment(_)));
-        self.emit_token(comment);
+    fn push_str(&mut self, str: &str) {
+        self.end += str.len();
     }
+}
 
-    fn emit_current_doctype(&mut self) {
-        let doctype = self.current_token.take().unwrap();
-        debug_assert!(matches!(doctype, Token::Doctype(_)));
-        self.emit_token(doctype);
-    }
+impl<R: Reader> Reader for PosTracker<R> {
+    type Error = R::Error;
 
-    fn set_self_closing(&mut self, reader: &R) {
-        let tag = self.current_token.as_mut().unwrap();
-        match tag {
-            Token::StartTag(StartTag {
-                ref mut self_closing,
-                ..
-            }) => {
-                *self_closing = true;
-            }
-            Token::EndTag(_) => {
-                self.emit_error(Error::EndTagWithTrailingSolidus, reader);
-            }
-            _ => {
-                debug_assert!(false);
-            }
-        }
-    }
-    fn set_force_quirks(&mut self) {
-        match self.current_token {
-            Some(Token::Doctype(ref mut doctype)) => doctype.force_quirks = true,
-            _ => debug_assert!(false),
-        }
-    }
-    fn push_tag_name(&mut self, s: &str) {
-        match self.current_token {
-            Some(Token::StartTag(StartTag {
-                ref mut name,
-                ref mut name_span,
-                ..
-            })) => {
-                name.push_str(s);
-                name_span.end += s.len();
-            }
-            Some(Token::EndTag(EndTag {
-                ref mut name,
-                ref mut name_span,
-                ..
-            })) => {
-                name.push_str(s);
-                name_span.end += s.len();
+    fn read_char(&mut self) -> Result<Option<char>, Self::Error> {
+        match self.reader.read_char()? {
+            Some(char) => {
+                self.position += char.len_utf8();
+                Ok(Some(char))
             }
-            _ => debug_assert!(false),
-        }
-    }
-
-    fn push_comment(&mut self, s: &str) {
-        match self.current_token {
-            Some(Token::Comment(ref mut data)) => data.push_str(s),
-            _ => debug_assert!(false),
-        }
-    }
-
-    fn push_doctype_name(&mut self, s: &str) {
-        match self.current_token {
-            Some(Token::Doctype(ref mut doctype)) => doctype.name.push_str(s),
-            _ => debug_assert!(false),
-        }
-    }
-    fn init_doctype(&mut self, _reader: &R) {
-        self.current_token = Some(Token::Doctype(Doctype {
-            name: String::new(),
-            force_quirks: false,
-            public_identifier: None,
-            system_identifier: None,
-        }));
-    }
-
-    fn init_attribute_name(&mut self, reader: &R) {
-        self.flush_current_attribute();
-        self.current_attribute = Some((
-            String::new(),
-            Attribute {
-                name_span: reader.get_pos() - 1..reader.get_pos() - 1,
-                ..Default::default()
-            },
-        ));
-    }
-
-    fn init_attribute_value(&mut self, reader: &R, quoted: bool) {
-        let current_attr = self.current_attribute.as_mut().unwrap();
-        let offset = if quoted { 0 } else { 1 };
-        current_attr.1.value_span = reader.get_pos() - offset..reader.get_pos() - offset;
-    }
-
-    fn push_attribute_name(&mut self, s: &str) {
-        let current_attr = self.current_attribute.as_mut().unwrap();
-        current_attr.0.push_str(s);
-        current_attr.1.name_span.end += s.len();
-    }
-    fn push_attribute_value(&mut self, s: &str) {
-        let current_attr = self.current_attribute.as_mut().unwrap();
-        current_attr.1.value.push_str(s);
-        current_attr.1.value_span.end += s.len();
-    }
-    fn set_doctype_public_identifier(&mut self, value: &str) {
-        if let Some(Token::Doctype(Doctype {
-            ref mut public_identifier,
-            ..
-        })) = self.current_token
-        {
-            *public_identifier = Some(value.to_owned());
-        } else {
-            debug_assert!(false);
-        }
-    }
-    fn set_doctype_system_identifier(&mut self, value: &str) {
-        if let Some(Token::Doctype(Doctype {
-            ref mut system_identifier,
-            ..
-        })) = self.current_token
-        {
-            *system_identifier = Some(value.to_owned());
-        } else {
-            debug_assert!(false);
-        }
-    }
-    fn push_doctype_public_identifier(&mut self, s: &str) {
-        if let Some(Token::Doctype(Doctype {
-            public_identifier: Some(ref mut id),
-            ..
-        })) = self.current_token
-        {
-            id.push_str(s);
-        } else {
-            debug_assert!(false);
-        }
-    }
-    fn push_doctype_system_identifier(&mut self, s: &str) {
-        if let Some(Token::Doctype(Doctype {
-            system_identifier: Some(ref mut id),
-            ..
-        })) = self.current_token
-        {
-            id.push_str(s);
-        } else {
-            debug_assert!(false);
+            None => Ok(None),
         }
     }
 
-    fn current_is_appropriate_end_tag_token(&mut self) -> bool {
-        match self.current_token {
-            Some(Token::EndTag(ref tag)) => {
-                !self.last_start_tag.is_empty() && self.last_start_tag == tag.name
+    fn try_read_string(&mut self, s: &str, case_sensitive: bool) -> Result<bool, Self::Error> {
+        match self.reader.try_read_string(s, case_sensitive)? {
+            true => {
+                self.position += s.len();
+                Ok(true)
             }
-            _ => false,
+            false => Ok(false),
         }
     }
 }