Create test runner which renders layouts to images 🗺

1 files changed, 698 insertions, 0 deletions

diff --git a/src/parsing/mod.rs b/src/parsing/mod.rs
new file mode 100644
index 00000000..344f3577
--- /dev/null
+++ b/src/parsing/mod.rs
@@ -0,0 +1,698 @@
+//! Parsing of source code into token streams an syntax trees.
+
+use std::collections::HashMap;
+use unicode_xid::UnicodeXID;
+
+use crate::func::{Function, Scope};
+use crate::syntax::*;
+use crate::size::Size;
+
+mod tokens;
+pub use tokens::{tokenize, Tokens};
+
+
+/// Parses source code into a syntax tree given a context.
+#[inline]
+pub fn parse(src: &str, ctx: ParseContext) -> ParseResult<SyntaxTree> {
+    Parser::new(src, ctx).parse()
+}
+
+/// The context for parsing.
+#[derive(Debug, Copy, Clone)]
+pub struct ParseContext<'a> {
+    /// The scope containing function definitions.
+    pub scope: &'a Scope,
+}
+
+/// Transforms token streams to syntax trees.
+#[derive(Debug)]
+struct Parser<'s> {
+    src: &'s str,
+    tokens: PeekableTokens<'s>,
+    state: ParserState,
+    ctx: ParseContext<'s>,
+    tree: SyntaxTree,
+}
+
+/// The state the parser is in.
+#[derive(Debug, Copy, Clone, Eq, PartialEq)]
+enum ParserState {
+    /// The base state of the parser.
+    Body,
+    /// We saw one newline already.
+    FirstNewline,
+    /// We wrote a newline.
+    WroteNewline,
+}
+
+impl<'s> Parser<'s> {
+    /// Create a new parser from the source and the context.
+    fn new(src: &'s str, ctx: ParseContext<'s>) -> Parser<'s> {
+        Parser {
+            src,
+            tokens: PeekableTokens::new(tokenize(src)),
+            state: ParserState::Body,
+            ctx,
+            tree: SyntaxTree::new(),
+        }
+    }
+
+    /// Parse the source into an abstract syntax tree.
+    fn parse(mut self) -> ParseResult<SyntaxTree> {
+        // Loop through all the tokens.
+        while self.tokens.peek().is_some() {
+            self.parse_white()?;
+            self.parse_body_part()?;
+        }
+
+        Ok(self.tree)
+    }
+
+    /// Parse the next part of the body.
+    fn parse_body_part(&mut self) -> ParseResult<()> {
+        if let Some(token) = self.tokens.peek() {
+            match token {
+                // Functions
+                Token::LeftBracket => self.parse_func()?,
+                Token::RightBracket => return Err(ParseError::new("unexpected closing bracket")),
+
+                // Modifiers
+                Token::Underscore => self.append_consumed(Node::ToggleItalics),
+                Token::Star => self.append_consumed(Node::ToggleBold),
+                Token::Backtick => self.append_consumed(Node::ToggleMonospace),
+
+                // Normal text
+                Token::Text(word) => self.append_consumed(Node::Text(word.to_owned())),
+
+                Token::Colon | Token::Equals => panic!("bad token for body: {:?}", token),
+
+                // The rest is handled elsewhere or should not happen, because `Tokens` does not
+                // yield colons or equals in the body, but their text equivalents instead.
+                _ => panic!("unexpected token: {:?}", token),
+            }
+        }
+        Ok(())
+    }
+
+    /// Parse a complete function from the current position.
+    fn parse_func(&mut self) -> ParseResult<()> {
+        // This should only be called if a left bracket was seen.
+        assert!(self.tokens.next() == Some(Token::LeftBracket));
+
+        let header = self.parse_func_header()?;
+        let body = self.parse_func_body(&header)?;
+
+        // Finally this function is parsed to the end.
+        self.append(Node::Func(FuncCall {
+            header,
+            body,
+        }));
+
+        Ok(self.switch(ParserState::Body))
+    }
+
+    /// Parse a function header.
+    fn parse_func_header(&mut self) -> ParseResult<FuncHeader> {
+        // The next token should be the name of the function.
+        self.skip_white();
+        let name = match self.tokens.next() {
+            Some(Token::Text(word)) => {
+                if is_identifier(word) {
+                    Ok(word.to_owned())
+                } else {
+                    Err(ParseError::new(format!("invalid identifier: '{}'", word)))
+                }
+            },
+            _ => Err(ParseError::new("expected identifier")),
+        }?;
+
+        let mut header = FuncHeader {
+            name,
+            args: vec![],
+            kwargs: HashMap::new(),
+        };
+
+        self.skip_white();
+
+        // Check for arguments
+        match self.tokens.next() {
+            Some(Token::RightBracket) => {},
+            Some(Token::Colon) => {
+                let (args, kwargs) = self.parse_func_args()?;
+                header.args = args;
+                header.kwargs = kwargs;
+            },
+            _ => return Err(ParseError::new("expected function arguments or closing bracket")),
+        }
+
+        // Store the header information of the function invocation.
+        Ok(header)
+    }
+
+    /// Parse the arguments to a function.
+    fn parse_func_args(&mut self) -> ParseResult<(Vec<Expression>, HashMap<String, Expression>)> {
+        let mut args = vec![];
+        let kwargs = HashMap::new();
+
+        let mut comma = false;
+        loop {
+            self.skip_white();
+
+            match self.tokens.peek() {
+                Some(Token::Text(_)) | Some(Token::Quoted(_)) if !comma => {
+                    args.push(self.parse_expression()?);
+                    comma = true;
+                },
+
+                Some(Token::Comma) if comma => {
+                    self.advance();
+                    comma = false
+                },
+                Some(Token::RightBracket) => {
+                    self.advance();
+                    break
+                },
+
+                _ if comma => return Err(ParseError::new("expected comma or closing bracket")),
+                _ => return Err(ParseError::new("expected closing bracket")),
+            }
+        }
+
+        Ok((args, kwargs))
+    }
+
+    /// Parse an expression.
+    fn parse_expression(&mut self) -> ParseResult<Expression> {
+        Ok(match self.tokens.next() {
+            Some(Token::Quoted(text)) => Expression::Str(text.to_owned()),
+            Some(Token::Text(text)) => {
+                if let Ok(b) = text.parse::<bool>() {
+                    Expression::Bool(b)
+                } else if let Ok(num) = text.parse::<f64>() {
+                    Expression::Number(num)
+                } else if let Ok(size) = text.parse::<Size>() {
+                    Expression::Size(size)
+                } else {
+                    Expression::Ident(text.to_owned())
+                }
+            },
+            _ => return Err(ParseError::new("expected expression")),
+        })
+    }
+
+    /// Parse the body of a function.
+    fn parse_func_body(&mut self, header: &FuncHeader) -> ParseResult<Box<dyn Function>> {
+        // Whether the function has a body.
+        let has_body = self.tokens.peek() == Some(Token::LeftBracket);
+        if has_body {
+            self.advance();
+        }
+
+        // Now we want to parse this function dynamically.
+        let parser = self.ctx.scope.get_parser(&header.name)
+            .ok_or_else(|| ParseError::new(format!("unknown function: '{}'", &header.name)))?;
+
+        // Do the parsing dependent on whether the function has a body.
+        Ok(if has_body {
+            // Find out the string which makes the body of this function.
+            let (start, end) = self.tokens.current_index().and_then(|index| {
+                find_closing_bracket(&self.src[index..])
+                    .map(|end| (index, index + end))
+            }).ok_or_else(|| ParseError::new("expected closing bracket"))?;
+
+            // Parse the body.
+            let body_string = &self.src[start .. end];
+            let body = parser(&header, Some(body_string), self.ctx)?;
+
+            // Skip to the end of the function in the token stream.
+            self.tokens.goto(end);
+
+            // Now the body should be closed.
+            assert!(self.tokens.next() == Some(Token::RightBracket));
+
+            body
+        } else {
+            parser(&header, None, self.ctx)?
+        })
+    }
+
+    /// Parse whitespace (as long as there is any) and skip over comments.
+    fn parse_white(&mut self) -> ParseResult<()> {
+        while let Some(token) = self.tokens.peek() {
+            match self.state {
+                ParserState::FirstNewline => match token {
+                    Token::Newline => {
+                        self.append_consumed(Node::Newline);
+                        self.switch(ParserState::WroteNewline);
+                    },
+                    Token::Space => self.append_space_consumed(),
+                    _ => {
+                        self.append_space();
+                        self.switch(ParserState::Body);
+                    },
+                },
+                ParserState::WroteNewline => match token {
+                    Token::Newline | Token::Space => self.append_space_consumed(),
+                    _ => self.switch(ParserState::Body),
+                },
+                ParserState::Body => match token {
+                    // Whitespace
+                    Token::Space => self.append_space_consumed(),
+                    Token::Newline => {
+                        self.advance();
+                        self.switch(ParserState::FirstNewline);
+                    },
+
+                    // Comments
+                    Token::LineComment(_) | Token::BlockComment(_) => self.advance(),
+                    Token::StarSlash => {
+                        return Err(ParseError::new("unexpected end of block comment"));
+                    },
+
+                    // Anything else skips out of the function.
+                    _ => break,
+                }
+            }
+        }
+
+        Ok(())
+    }
+
+    /// Skip over whitespace and comments.
+    fn skip_white(&mut self) {
+        while let Some(token) = self.tokens.peek() {
+            match token {
+                Token::Space | Token::Newline
+                | Token::LineComment(_) | Token::BlockComment(_) => self.advance(),
+                _ => break,
+            }
+        }
+    }
+
+    /// Advance the iterator by one step.
+    fn advance(&mut self) {
+        self.tokens.next();
+    }
+
+    /// Switch the state.
+    fn switch(&mut self, state: ParserState) {
+        self.state = state;
+    }
+
+    /// Append a node to the tree.
+    fn append(&mut self, node: Node) {
+        self.tree.nodes.push(node);
+    }
+
+    /// Append a space if there is not one already.
+    fn append_space(&mut self) {
+        if self.tree.nodes.last() != Some(&Node::Space) {
+            self.append(Node::Space);
+        }
+    }
+
+    /// Advance and return the given node.
+    fn append_consumed(&mut self, node: Node) {
+        self.advance();
+        self.append(node);
+    }
+
+    /// Advance and append a space if there is not one already.
+    fn append_space_consumed(&mut self) {
+        self.advance();
+        self.append_space();
+    }
+}
+
+/// Find the index of the first unbalanced and unescaped closing bracket.
+fn find_closing_bracket(src: &str) -> Option<usize> {
+    let mut parens = 0;
+    let mut escaped = false;
+    for (index, c) in src.char_indices() {
+        match c {
+            '\\' => {
+                escaped = !escaped;
+                continue;
+            },
+            ']' if !escaped && parens == 0 => return Some(index),
+            '[' if !escaped => parens += 1,
+            ']' if !escaped => parens -= 1,
+            _ => {},
+        }
+        escaped = false;
+    }
+    None
+}
+
+/// A peekable iterator for tokens which allows access to the original iterator inside this module
+/// (which is needed by the parser).
+#[derive(Debug, Clone)]
+struct PeekableTokens<'s> {
+    tokens: Tokens<'s>,
+    peeked: Option<Option<Token<'s>>>,
+}
+
+impl<'s> PeekableTokens<'s> {
+    /// Create a new iterator from a string.
+    fn new(tokens: Tokens<'s>) -> PeekableTokens<'s> {
+        PeekableTokens {
+            tokens,
+            peeked: None,
+        }
+    }
+
+    /// Peek at the next element.
+    fn peek(&mut self) -> Option<Token<'s>> {
+        let iter = &mut self.tokens;
+        *self.peeked.get_or_insert_with(|| iter.next())
+    }
+
+    /// The index of the first character of the next token in the source string.
+    fn current_index(&mut self) -> Option<usize> {
+        self.tokens.chars.current_index()
+    }
+
+    /// Go to a new position in the underlying string.
+    fn goto(&mut self, index: usize) {
+        self.tokens.chars.goto(index);
+        self.peeked = None;
+    }
+}
+
+impl<'s> Iterator for PeekableTokens<'s> {
+    type Item = Token<'s>;
+
+    fn next(&mut self) -> Option<Token<'s>> {
+        match self.peeked.take() {
+            Some(value) => value,
+            None => self.tokens.next(),
+        }
+    }
+}
+
+/// Whether this word is a valid unicode identifier.
+fn is_identifier(string: &str) -> bool {
+    let mut chars = string.chars();
+
+    match chars.next() {
+        Some(c) if !UnicodeXID::is_xid_start(c) => return false,
+        None => return false,
+        _ => (),
+    }
+
+    while let Some(c) = chars.next() {
+        if !UnicodeXID::is_xid_continue(c) {
+            return false;
+        }
+    }
+
+    true
+}
+
+
+/// The error type for parsing.
+pub struct ParseError(String);
+
+/// The result type for parsing.
+pub type ParseResult<T> = Result<T, ParseError>;
+
+impl ParseError {
+    /// Create a new parse error with a message.
+    pub fn new<S: Into<String>>(message: S) -> ParseError {
+        ParseError(message.into())
+    }
+}
+
+error_type! {
+    err: ParseError,
+    show: f => f.write_str(&err.0),
+}
+
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::func::{Function, Scope};
+    use crate::layout::{LayoutContext, LayoutResult, Layout};
+    use Node::{Space as S, Newline as N, Func as F};
+    use funcs::*;
+
+    /// Two test functions, one which parses it's body as another syntax tree and another one which
+    /// does not expect a body.
+    mod funcs {
+        use super::*;
+
+        /// A testing function which just parses it's body into a syntax tree.
+        #[derive(Debug, PartialEq)]
+        pub struct TreeFn(pub SyntaxTree);
+
+        impl Function for TreeFn {
+            fn parse(_: &FuncHeader, body: Option<&str>, ctx: ParseContext)
+                -> ParseResult<Self> where Self: Sized {
+                if let Some(src) = body {
+                    parse(src, ctx).map(|tree| TreeFn(tree))
+                } else {
+                    Err(ParseError::new("expected body for tree fn"))
+                }
+            }
+
+            fn layout(&self, _: LayoutContext) -> LayoutResult<Option<Layout>> { Ok(None) }
+        }
+
+        /// A testing function without a body.
+        #[derive(Debug, PartialEq)]
+        pub struct BodylessFn;
+
+        impl Function for BodylessFn {
+            fn parse(_: &FuncHeader, body: Option<&str>, _: ParseContext)
+                -> ParseResult<Self> where Self: Sized {
+                if body.is_none() {
+                    Ok(BodylessFn)
+                } else {
+                    Err(ParseError::new("unexpected body for bodyless fn"))
+                }
+            }
+
+            fn layout(&self, _: LayoutContext) -> LayoutResult<Option<Layout>> { Ok(None) }
+        }
+    }
+
+    /// Test if the source code parses into the syntax tree.
+    fn test(src: &str, tree: SyntaxTree) {
+        let ctx = ParseContext { scope: &Scope::new() };
+        assert_eq!(parse(src, ctx).unwrap(), tree);
+    }
+
+    /// Test with a scope containing function definitions.
+    fn test_scoped(scope: &Scope, src: &str, tree: SyntaxTree) {
+        let ctx = ParseContext { scope };
+        assert_eq!(parse(src, ctx).unwrap(), tree);
+    }
+
+    /// Test if the source parses into the error.
+    fn test_err(src: &str, err: &str) {
+        let ctx = ParseContext { scope: &Scope::new() };
+        assert_eq!(parse(src, ctx).unwrap_err().to_string(), err);
+    }
+
+    /// Test with a scope if the source parses into the error.
+    fn test_err_scoped(scope: &Scope, src: &str, err: &str) {
+        let ctx = ParseContext { scope };
+        assert_eq!(parse(src, ctx).unwrap_err().to_string(), err);
+    }
+
+    /// Create a text node.
+    #[allow(non_snake_case)]
+    fn T(s: &str) -> Node { Node::Text(s.to_owned()) }
+
+    /// Shortcut macro to create a syntax tree. Is `vec`-like and the elements are the nodes.
+    macro_rules! tree {
+        ($($x:expr),*) => (
+            SyntaxTree { nodes: vec![$($x),*] }
+        );
+        ($($x:expr,)*) => (tree![$($x),*])
+    }
+
+    /// Shortcut macro to create a function.
+    macro_rules! func {
+        (name => $name:expr, body => None $(,)*) => {
+            func!(@$name, Box::new(BodylessFn))
+        };
+        (name => $name:expr, body => $tree:expr $(,)*) => {
+            func!(@$name, Box::new(TreeFn($tree)))
+        };
+        (@$name:expr, $body:expr) => {
+            FuncCall {
+                header: FuncHeader {
+                    name: $name.to_string(),
+                    args: vec![],
+                    kwargs: HashMap::new(),
+                },
+                body: $body,
+            }
+        }
+    }
+
+    /// Parse the basic cases.
+    #[test]
+    fn parse_base() {
+        test("", tree! []);
+        test("Hello World!", tree! [ T("Hello"), S, T("World!") ]);
+    }
+
+    /// Test whether newlines generate the correct whitespace.
+    #[test]
+    fn parse_newlines_whitespace() {
+        test("Hello\nWorld", tree! [ T("Hello"), S, T("World") ]);
+        test("Hello \n World", tree! [ T("Hello"), S, T("World") ]);
+        test("Hello\n\nWorld", tree! [ T("Hello"), N, T("World") ]);
+        test("Hello \n\nWorld", tree! [ T("Hello"), S, N, T("World") ]);
+        test("Hello\n\n  World", tree! [ T("Hello"), N, S, T("World") ]);
+        test("Hello \n \n \n  World", tree! [ T("Hello"), S, N, S, T("World") ]);
+        test("Hello\n \n\n  World", tree! [ T("Hello"), S, N, S, T("World") ]);
+    }
+
+    /// Parse things dealing with functions.
+    #[test]
+    fn parse_functions() {
+        let mut scope = Scope::new();
+        scope.add::<BodylessFn>("test");
+        scope.add::<BodylessFn>("end");
+        scope.add::<TreeFn>("modifier");
+        scope.add::<TreeFn>("func");
+
+        test_scoped(&scope,"[test]", tree! [ F(func! { name => "test", body => None }) ]);
+        test_scoped(&scope,"[ test]", tree! [ F(func! { name => "test", body => None }) ]);
+        test_scoped(&scope, "This is an [modifier][example] of a function invocation.", tree! [
+            T("This"), S, T("is"), S, T("an"), S,
+            F(func! { name => "modifier", body => tree! [ T("example") ] }), S,
+            T("of"), S, T("a"), S, T("function"), S, T("invocation.")
+        ]);
+        test_scoped(&scope, "[func][Hello][modifier][Here][end]",  tree! [
+            F(func! { name => "func", body => tree! [ T("Hello") ] }),
+            F(func! { name => "modifier", body => tree! [ T("Here") ] }),
+            F(func! { name => "end", body => None }),
+        ]);
+        test_scoped(&scope, "[func][]", tree! [ F(func! { name => "func", body => tree! [] }) ]);
+        test_scoped(&scope, "[modifier][[func][call]] outside", tree! [
+            F(func! {
+                name => "modifier",
+                body => tree! [ F(func! { name => "func", body => tree! [ T("call") ] }) ],
+            }),
+            S, T("outside")
+        ]);
+
+    }
+
+    /// Parse functions with arguments.
+    #[test]
+    fn parse_function_args() {
+        use Expression::{Number as N, Size as Z, Bool as B};
+
+        #[allow(non_snake_case)]
+        fn S(string: &str) -> Expression { Expression::Str(string.to_owned()) }
+        #[allow(non_snake_case)]
+        fn I(string: &str) -> Expression { Expression::Ident(string.to_owned()) }
+
+        fn func(name: &str, args: Vec<Expression>) -> SyntaxTree {
+            tree! [ F(FuncCall {
+                header: FuncHeader {
+                    name: name.to_string(),
+                    args,
+                    kwargs: HashMap::new(),
+                },
+                body: Box::new(BodylessFn)
+            }) ]
+        }
+
+        let mut scope = Scope::new();
+        scope.add::<BodylessFn>("align");
+
+        test_scoped(&scope, "[align: left]", func("align", vec![I("left")]));
+        test_scoped(&scope, "[align: left,right]", func("align", vec![I("left"), I("right")]));
+        test_scoped(&scope, "[align: left, right]", func("align", vec![I("left"), I("right")]));
+        test_scoped(&scope, "[align: \"hello\"]", func("align", vec![S("hello")]));
+        test_scoped(&scope, r#"[align: "hello\"world"]"#, func("align", vec![S(r#"hello\"world"#)]));
+        test_scoped(&scope, "[align: 12]", func("align", vec![N(12.0)]));
+        test_scoped(&scope, "[align: 17.53pt]", func("align", vec![Z(Size::pt(17.53))]));
+        test_scoped(&scope, "[align: 2.4in]", func("align", vec![Z(Size::inches(2.4))]));
+        test_scoped(&scope, "[align: true, 10mm, left, \"hi, there\"]",
+            func("align", vec![B(true), Z(Size::mm(10.0)), I("left"), S("hi, there")]));
+    }
+
+    /// Parse comments (line and block).
+    #[test]
+    fn parse_comments() {
+        let mut scope = Scope::new();
+        scope.add::<BodylessFn>("test");
+        scope.add::<TreeFn>("func");
+
+        test_scoped(&scope, "Text\n// Comment\n More text",
+            tree! [ T("Text"), S, T("More"), S, T("text") ]);
+        test_scoped(&scope, "[test/*world*/]",
+            tree! [ F(func! { name => "test", body => None }) ]);
+        test_scoped(&scope, "[test/*]*/]",
+            tree! [ F(func! { name => "test", body => None }) ]);
+    }
+
+    /// Test if escaped, but unbalanced parens are correctly parsed.
+    #[test]
+    fn parse_unbalanced_body_parens() {
+        let mut scope = Scope::new();
+        scope.add::<TreeFn>("code");
+
+        test_scoped(&scope, r"My [code][Close \]] end", tree! [
+            T("My"), S, F(func! {
+                name => "code",
+                body => tree! [ T("Close"), S, T("]") ]
+            }), S, T("end")
+        ]);
+        test_scoped(&scope, r"My [code][\[ Open] end", tree! [
+            T("My"), S, F(func! {
+                name => "code",
+                body => tree! [ T("["), S, T("Open") ]
+            }), S, T("end")
+        ]);
+        test_scoped(&scope, r"My [code][Open \]  and  \[ close]end", tree! [
+            T("My"), S, F(func! {
+                name => "code",
+                body => tree! [ T("Open"), S, T("]"), S, T("and"), S, T("["), S, T("close") ]
+            }), T("end")
+        ]);
+    }
+
+    /// Tests if the parser handles non-ASCII stuff correctly.
+    #[test]
+    fn parse_unicode() {
+        let mut scope = Scope::new();
+        scope.add::<BodylessFn>("func");
+        scope.add::<TreeFn>("bold");
+
+        test_scoped(&scope, "[func] ⺐.", tree! [
+            F(func! {
+                name => "func",
+                body => None,
+            }),
+            S, T("⺐.")
+        ]);
+        test_scoped(&scope, "[bold][Hello 🌍!]", tree! [
+            F(func! {
+                name => "bold",
+                body => tree! [ T("Hello"), S, T("🌍!") ],
+            })
+        ]);
+    }
+
+    /// Tests whether errors get reported correctly.
+    #[test]
+    fn parse_errors() {
+        let mut scope = Scope::new();
+        scope.add::<TreeFn>("hello");
+
+        test_err("No functions here]", "unexpected closing bracket");
+        test_err_scoped(&scope, "[hello][world", "expected closing bracket");
+        test_err("[hello world", "expected function arguments or closing bracket");
+        test_err("[ no-name][Why?]", "invalid identifier: 'no-name'");
+        test_err("Hello */", "unexpected end of block comment");
+    }
+}