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Diffstat (limited to 'compiler/rustc_graphviz/src/lib.rs')
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diff --git a/compiler/rustc_graphviz/src/lib.rs b/compiler/rustc_graphviz/src/lib.rs new file mode 100644 index 000000000..6eaff5c2f --- /dev/null +++ b/compiler/rustc_graphviz/src/lib.rs @@ -0,0 +1,693 @@ +//! Generate files suitable for use with [Graphviz](https://www.graphviz.org/) +//! +//! The `render` function generates output (e.g., an `output.dot` file) for +//! use with [Graphviz](https://www.graphviz.org/) by walking a labeled +//! graph. (Graphviz can then automatically lay out the nodes and edges +//! of the graph, and also optionally render the graph as an image or +//! other [output formats](https://www.graphviz.org/docs/outputs), such as SVG.) +//! +//! Rather than impose some particular graph data structure on clients, +//! this library exposes two traits that clients can implement on their +//! own structs before handing them over to the rendering function. +//! +//! Note: This library does not yet provide access to the full +//! expressiveness of the [DOT language](https://www.graphviz.org/doc/info/lang.html). +//! For example, there are many [attributes](https://www.graphviz.org/doc/info/attrs.html) +//! related to providing layout hints (e.g., left-to-right versus top-down, which +//! algorithm to use, etc). The current intention of this library is to +//! emit a human-readable .dot file with very regular structure suitable +//! for easy post-processing. +//! +//! # Examples +//! +//! The first example uses a very simple graph representation: a list of +//! pairs of ints, representing the edges (the node set is implicit). +//! Each node label is derived directly from the int representing the node, +//! while the edge labels are all empty strings. +//! +//! This example also illustrates how to use `Cow<[T]>` to return +//! an owned vector or a borrowed slice as appropriate: we construct the +//! node vector from scratch, but borrow the edge list (rather than +//! constructing a copy of all the edges from scratch). +//! +//! The output from this example renders five nodes, with the first four +//! forming a diamond-shaped acyclic graph and then pointing to the fifth +//! which is cyclic. +//! +//! ```rust +//! #![feature(rustc_private)] +//! +//! use std::io::Write; +//! use rustc_graphviz as dot; +//! +//! type Nd = isize; +//! type Ed = (isize,isize); +//! struct Edges(Vec<Ed>); +//! +//! pub fn render_to<W: Write>(output: &mut W) { +//! let edges = Edges(vec![(0,1), (0,2), (1,3), (2,3), (3,4), (4,4)]); +//! dot::render(&edges, output).unwrap() +//! } +//! +//! impl<'a> dot::Labeller<'a> for Edges { +//! type Node = Nd; +//! type Edge = Ed; +//! fn graph_id(&'a self) -> dot::Id<'a> { dot::Id::new("example1").unwrap() } +//! +//! fn node_id(&'a self, n: &Nd) -> dot::Id<'a> { +//! dot::Id::new(format!("N{}", *n)).unwrap() +//! } +//! } +//! +//! impl<'a> dot::GraphWalk<'a> for Edges { +//! type Node = Nd; +//! type Edge = Ed; +//! fn nodes(&self) -> dot::Nodes<'a,Nd> { +//! // (assumes that |N| \approxeq |E|) +//! let &Edges(ref v) = self; +//! let mut nodes = Vec::with_capacity(v.len()); +//! for &(s,t) in v { +//! nodes.push(s); nodes.push(t); +//! } +//! nodes.sort(); +//! nodes.dedup(); +//! nodes.into() +//! } +//! +//! fn edges(&'a self) -> dot::Edges<'a,Ed> { +//! let &Edges(ref edges) = self; +//! (&edges[..]).into() +//! } +//! +//! fn source(&self, e: &Ed) -> Nd { let &(s,_) = e; s } +//! +//! fn target(&self, e: &Ed) -> Nd { let &(_,t) = e; t } +//! } +//! +//! # pub fn main() { render_to(&mut Vec::new()) } +//! ``` +//! +//! ```no_run +//! # pub fn render_to<W:std::io::Write>(output: &mut W) { unimplemented!() } +//! pub fn main() { +//! use std::fs::File; +//! let mut f = File::create("example1.dot").unwrap(); +//! render_to(&mut f) +//! } +//! ``` +//! +//! Output from first example (in `example1.dot`): +//! +//! ```dot +//! digraph example1 { +//! N0[label="N0"]; +//! N1[label="N1"]; +//! N2[label="N2"]; +//! N3[label="N3"]; +//! N4[label="N4"]; +//! N0 -> N1[label=""]; +//! N0 -> N2[label=""]; +//! N1 -> N3[label=""]; +//! N2 -> N3[label=""]; +//! N3 -> N4[label=""]; +//! N4 -> N4[label=""]; +//! } +//! ``` +//! +//! The second example illustrates using `node_label` and `edge_label` to +//! add labels to the nodes and edges in the rendered graph. The graph +//! here carries both `nodes` (the label text to use for rendering a +//! particular node), and `edges` (again a list of `(source,target)` +//! indices). +//! +//! This example also illustrates how to use a type (in this case the edge +//! type) that shares substructure with the graph: the edge type here is a +//! direct reference to the `(source,target)` pair stored in the graph's +//! internal vector (rather than passing around a copy of the pair +//! itself). Note that this implies that `fn edges(&'a self)` must +//! construct a fresh `Vec<&'a (usize,usize)>` from the `Vec<(usize,usize)>` +//! edges stored in `self`. +//! +//! Since both the set of nodes and the set of edges are always +//! constructed from scratch via iterators, we use the `collect()` method +//! from the `Iterator` trait to collect the nodes and edges into freshly +//! constructed growable `Vec` values (rather than using `Cow` as in the +//! first example above). +//! +//! The output from this example renders four nodes that make up the +//! Hasse-diagram for the subsets of the set `{x, y}`. Each edge is +//! labeled with the ⊆ character (specified using the HTML character +//! entity `&sube`). +//! +//! ```rust +//! #![feature(rustc_private)] +//! +//! use std::io::Write; +//! use rustc_graphviz as dot; +//! +//! type Nd = usize; +//! type Ed<'a> = &'a (usize, usize); +//! struct Graph { nodes: Vec<&'static str>, edges: Vec<(usize,usize)> } +//! +//! pub fn render_to<W: Write>(output: &mut W) { +//! let nodes = vec!["{x,y}","{x}","{y}","{}"]; +//! let edges = vec![(0,1), (0,2), (1,3), (2,3)]; +//! let graph = Graph { nodes: nodes, edges: edges }; +//! +//! dot::render(&graph, output).unwrap() +//! } +//! +//! impl<'a> dot::Labeller<'a> for Graph { +//! type Node = Nd; +//! type Edge = Ed<'a>; +//! fn graph_id(&'a self) -> dot::Id<'a> { dot::Id::new("example2").unwrap() } +//! fn node_id(&'a self, n: &Nd) -> dot::Id<'a> { +//! dot::Id::new(format!("N{}", n)).unwrap() +//! } +//! fn node_label<'b>(&'b self, n: &Nd) -> dot::LabelText<'b> { +//! dot::LabelText::LabelStr(self.nodes[*n].into()) +//! } +//! fn edge_label<'b>(&'b self, _: &Ed) -> dot::LabelText<'b> { +//! dot::LabelText::LabelStr("⊆".into()) +//! } +//! } +//! +//! impl<'a> dot::GraphWalk<'a> for Graph { +//! type Node = Nd; +//! type Edge = Ed<'a>; +//! fn nodes(&self) -> dot::Nodes<'a,Nd> { (0..self.nodes.len()).collect() } +//! fn edges(&'a self) -> dot::Edges<'a,Ed<'a>> { self.edges.iter().collect() } +//! fn source(&self, e: &Ed) -> Nd { let & &(s,_) = e; s } +//! fn target(&self, e: &Ed) -> Nd { let & &(_,t) = e; t } +//! } +//! +//! # pub fn main() { render_to(&mut Vec::new()) } +//! ``` +//! +//! ```no_run +//! # pub fn render_to<W:std::io::Write>(output: &mut W) { unimplemented!() } +//! pub fn main() { +//! use std::fs::File; +//! let mut f = File::create("example2.dot").unwrap(); +//! render_to(&mut f) +//! } +//! ``` +//! +//! The third example is similar to the second, except now each node and +//! edge now carries a reference to the string label for each node as well +//! as that node's index. (This is another illustration of how to share +//! structure with the graph itself, and why one might want to do so.) +//! +//! The output from this example is the same as the second example: the +//! Hasse-diagram for the subsets of the set `{x, y}`. +//! +//! ```rust +//! #![feature(rustc_private)] +//! +//! use std::io::Write; +//! use rustc_graphviz as dot; +//! +//! type Nd<'a> = (usize, &'a str); +//! type Ed<'a> = (Nd<'a>, Nd<'a>); +//! struct Graph { nodes: Vec<&'static str>, edges: Vec<(usize,usize)> } +//! +//! pub fn render_to<W: Write>(output: &mut W) { +//! let nodes = vec!["{x,y}","{x}","{y}","{}"]; +//! let edges = vec![(0,1), (0,2), (1,3), (2,3)]; +//! let graph = Graph { nodes: nodes, edges: edges }; +//! +//! dot::render(&graph, output).unwrap() +//! } +//! +//! impl<'a> dot::Labeller<'a> for Graph { +//! type Node = Nd<'a>; +//! type Edge = Ed<'a>; +//! fn graph_id(&'a self) -> dot::Id<'a> { dot::Id::new("example3").unwrap() } +//! fn node_id(&'a self, n: &Nd<'a>) -> dot::Id<'a> { +//! dot::Id::new(format!("N{}", n.0)).unwrap() +//! } +//! fn node_label<'b>(&'b self, n: &Nd<'b>) -> dot::LabelText<'b> { +//! let &(i, _) = n; +//! dot::LabelText::LabelStr(self.nodes[i].into()) +//! } +//! fn edge_label<'b>(&'b self, _: &Ed<'b>) -> dot::LabelText<'b> { +//! dot::LabelText::LabelStr("⊆".into()) +//! } +//! } +//! +//! impl<'a> dot::GraphWalk<'a> for Graph { +//! type Node = Nd<'a>; +//! type Edge = Ed<'a>; +//! fn nodes(&'a self) -> dot::Nodes<'a,Nd<'a>> { +//! self.nodes.iter().map(|s| &s[..]).enumerate().collect() +//! } +//! fn edges(&'a self) -> dot::Edges<'a,Ed<'a>> { +//! self.edges.iter() +//! .map(|&(i,j)|((i, &self.nodes[i][..]), +//! (j, &self.nodes[j][..]))) +//! .collect() +//! } +//! fn source(&self, e: &Ed<'a>) -> Nd<'a> { let &(s,_) = e; s } +//! fn target(&self, e: &Ed<'a>) -> Nd<'a> { let &(_,t) = e; t } +//! } +//! +//! # pub fn main() { render_to(&mut Vec::new()) } +//! ``` +//! +//! ```no_run +//! # pub fn render_to<W:std::io::Write>(output: &mut W) { unimplemented!() } +//! pub fn main() { +//! use std::fs::File; +//! let mut f = File::create("example3.dot").unwrap(); +//! render_to(&mut f) +//! } +//! ``` +//! +//! # References +//! +//! * [Graphviz](https://www.graphviz.org/) +//! +//! * [DOT language](https://www.graphviz.org/doc/info/lang.html) + +#![doc( + html_root_url = "https://doc.rust-lang.org/nightly/nightly-rustc/", + test(attr(allow(unused_variables), deny(warnings))) +)] + +use LabelText::*; + +use std::borrow::Cow; +use std::io; +use std::io::prelude::*; + +/// The text for a graphviz label on a node or edge. +pub enum LabelText<'a> { + /// This kind of label preserves the text directly as is. + /// + /// Occurrences of backslashes (`\`) are escaped, and thus appear + /// as backslashes in the rendered label. + LabelStr(Cow<'a, str>), + + /// This kind of label uses the graphviz label escString type: + /// <https://www.graphviz.org/docs/attr-types/escString> + /// + /// Occurrences of backslashes (`\`) are not escaped; instead they + /// are interpreted as initiating an escString escape sequence. + /// + /// Escape sequences of particular interest: in addition to `\n` + /// to break a line (centering the line preceding the `\n`), there + /// are also the escape sequences `\l` which left-justifies the + /// preceding line and `\r` which right-justifies it. + EscStr(Cow<'a, str>), + + /// This uses a graphviz [HTML string label][html]. The string is + /// printed exactly as given, but between `<` and `>`. **No + /// escaping is performed.** + /// + /// [html]: https://www.graphviz.org/doc/info/shapes.html#html + HtmlStr(Cow<'a, str>), +} + +/// The style for a node or edge. +/// See <https://www.graphviz.org/docs/attr-types/style/> for descriptions. +/// Note that some of these are not valid for edges. +#[derive(Copy, Clone, PartialEq, Eq, Debug)] +pub enum Style { + None, + Solid, + Dashed, + Dotted, + Bold, + Rounded, + Diagonals, + Filled, + Striped, + Wedged, +} + +impl Style { + pub fn as_slice(self) -> &'static str { + match self { + Style::None => "", + Style::Solid => "solid", + Style::Dashed => "dashed", + Style::Dotted => "dotted", + Style::Bold => "bold", + Style::Rounded => "rounded", + Style::Diagonals => "diagonals", + Style::Filled => "filled", + Style::Striped => "striped", + Style::Wedged => "wedged", + } + } +} + +// There is a tension in the design of the labelling API. +// +// For example, I considered making a `Labeller<T>` trait that +// provides labels for `T`, and then making the graph type `G` +// implement `Labeller<Node>` and `Labeller<Edge>`. However, this is +// not possible without functional dependencies. (One could work +// around that, but I did not explore that avenue heavily.) +// +// Another approach that I actually used for a while was to make a +// `Label<Context>` trait that is implemented by the client-specific +// Node and Edge types (as well as an implementation on Graph itself +// for the overall name for the graph). The main disadvantage of this +// second approach (compared to having the `G` type parameter +// implement a Labelling service) that I have encountered is that it +// makes it impossible to use types outside of the current crate +// directly as Nodes/Edges; you need to wrap them in newtype'd +// structs. See e.g., the `No` and `Ed` structs in the examples. (In +// practice clients using a graph in some other crate would need to +// provide some sort of adapter shim over the graph anyway to +// interface with this library). +// +// Another approach would be to make a single `Labeller<N,E>` trait +// that provides three methods (graph_label, node_label, edge_label), +// and then make `G` implement `Labeller<N,E>`. At first this did not +// appeal to me, since I had thought I would need separate methods on +// each data variant for dot-internal identifiers versus user-visible +// labels. However, the identifier/label distinction only arises for +// nodes; graphs themselves only have identifiers, and edges only have +// labels. +// +// So in the end I decided to use the third approach described above. + +/// `Id` is a Graphviz `ID`. +pub struct Id<'a> { + name: Cow<'a, str>, +} + +impl<'a> Id<'a> { + /// Creates an `Id` named `name`. + /// + /// The caller must ensure that the input conforms to an + /// identifier format: it must be a non-empty string made up of + /// alphanumeric or underscore characters, not beginning with a + /// digit (i.e., the regular expression `[a-zA-Z_][a-zA-Z_0-9]*`). + /// + /// (Note: this format is a strict subset of the `ID` format + /// defined by the DOT language. This function may change in the + /// future to accept a broader subset, or the entirety, of DOT's + /// `ID` format.) + /// + /// Passing an invalid string (containing spaces, brackets, + /// quotes, ...) will return an empty `Err` value. + pub fn new<Name: Into<Cow<'a, str>>>(name: Name) -> Result<Id<'a>, ()> { + let name = name.into(); + match name.chars().next() { + Some(c) if c.is_ascii_alphabetic() || c == '_' => {} + _ => return Err(()), + } + if !name.chars().all(|c| c.is_ascii_alphanumeric() || c == '_') { + return Err(()); + } + + Ok(Id { name }) + } + + pub fn as_slice(&'a self) -> &'a str { + &*self.name + } +} + +/// Each instance of a type that implements `Label<C>` maps to a +/// unique identifier with respect to `C`, which is used to identify +/// it in the generated .dot file. They can also provide more +/// elaborate (and non-unique) label text that is used in the graphviz +/// rendered output. + +/// The graph instance is responsible for providing the DOT compatible +/// identifiers for the nodes and (optionally) rendered labels for the nodes and +/// edges, as well as an identifier for the graph itself. +pub trait Labeller<'a> { + type Node; + type Edge; + + /// Must return a DOT compatible identifier naming the graph. + fn graph_id(&'a self) -> Id<'a>; + + /// Maps `n` to a unique identifier with respect to `self`. The + /// implementor is responsible for ensuring that the returned name + /// is a valid DOT identifier. + fn node_id(&'a self, n: &Self::Node) -> Id<'a>; + + /// Maps `n` to one of the [graphviz `shape` names][1]. If `None` + /// is returned, no `shape` attribute is specified. + /// + /// [1]: https://www.graphviz.org/doc/info/shapes.html + fn node_shape(&'a self, _node: &Self::Node) -> Option<LabelText<'a>> { + None + } + + /// Maps `n` to a label that will be used in the rendered output. + /// The label need not be unique, and may be the empty string; the + /// default is just the output from `node_id`. + fn node_label(&'a self, n: &Self::Node) -> LabelText<'a> { + LabelStr(self.node_id(n).name) + } + + /// Maps `e` to a label that will be used in the rendered output. + /// The label need not be unique, and may be the empty string; the + /// default is in fact the empty string. + fn edge_label(&'a self, _e: &Self::Edge) -> LabelText<'a> { + LabelStr("".into()) + } + + /// Maps `n` to a style that will be used in the rendered output. + fn node_style(&'a self, _n: &Self::Node) -> Style { + Style::None + } + + /// Maps `e` to a style that will be used in the rendered output. + fn edge_style(&'a self, _e: &Self::Edge) -> Style { + Style::None + } +} + +/// Escape tags in such a way that it is suitable for inclusion in a +/// Graphviz HTML label. +pub fn escape_html(s: &str) -> String { + s.replace('&', "&").replace('\"', """).replace('<', "<").replace('>', ">") +} + +impl<'a> LabelText<'a> { + pub fn label<S: Into<Cow<'a, str>>>(s: S) -> LabelText<'a> { + LabelStr(s.into()) + } + + pub fn html<S: Into<Cow<'a, str>>>(s: S) -> LabelText<'a> { + HtmlStr(s.into()) + } + + fn escape_char<F>(c: char, mut f: F) + where + F: FnMut(char), + { + match c { + // not escaping \\, since Graphviz escString needs to + // interpret backslashes; see EscStr above. + '\\' => f(c), + _ => { + for c in c.escape_default() { + f(c) + } + } + } + } + fn escape_str(s: &str) -> String { + let mut out = String::with_capacity(s.len()); + for c in s.chars() { + LabelText::escape_char(c, |c| out.push(c)); + } + out + } + + /// Renders text as string suitable for a label in a .dot file. + /// This includes quotes or suitable delimiters. + pub fn to_dot_string(&self) -> String { + match *self { + LabelStr(ref s) => format!("\"{}\"", s.escape_default()), + EscStr(ref s) => format!("\"{}\"", LabelText::escape_str(&s)), + HtmlStr(ref s) => format!("<{}>", s), + } + } + + /// Decomposes content into string suitable for making EscStr that + /// yields same content as self. The result obeys the law + /// render(`lt`) == render(`EscStr(lt.pre_escaped_content())`) for + /// all `lt: LabelText`. + fn pre_escaped_content(self) -> Cow<'a, str> { + match self { + EscStr(s) => s, + LabelStr(s) => { + if s.contains('\\') { + (&*s).escape_default().to_string().into() + } else { + s + } + } + HtmlStr(s) => s, + } + } + + /// Puts `suffix` on a line below this label, with a blank line separator. + pub fn suffix_line(self, suffix: LabelText<'_>) -> LabelText<'static> { + let mut prefix = self.pre_escaped_content().into_owned(); + let suffix = suffix.pre_escaped_content(); + prefix.push_str(r"\n\n"); + prefix.push_str(&suffix); + EscStr(prefix.into()) + } +} + +pub type Nodes<'a, N> = Cow<'a, [N]>; +pub type Edges<'a, E> = Cow<'a, [E]>; + +// (The type parameters in GraphWalk should be associated items, +// when/if Rust supports such.) + +/// GraphWalk is an abstraction over a directed graph = (nodes,edges) +/// made up of node handles `N` and edge handles `E`, where each `E` +/// can be mapped to its source and target nodes. +/// +/// The lifetime parameter `'a` is exposed in this trait (rather than +/// introduced as a generic parameter on each method declaration) so +/// that a client impl can choose `N` and `E` that have substructure +/// that is bound by the self lifetime `'a`. +/// +/// The `nodes` and `edges` method each return instantiations of +/// `Cow<[T]>` to leave implementors the freedom to create +/// entirely new vectors or to pass back slices into internally owned +/// vectors. +pub trait GraphWalk<'a> { + type Node: Clone; + type Edge: Clone; + + /// Returns all the nodes in this graph. + fn nodes(&'a self) -> Nodes<'a, Self::Node>; + /// Returns all of the edges in this graph. + fn edges(&'a self) -> Edges<'a, Self::Edge>; + /// The source node for `edge`. + fn source(&'a self, edge: &Self::Edge) -> Self::Node; + /// The target node for `edge`. + fn target(&'a self, edge: &Self::Edge) -> Self::Node; +} + +#[derive(Clone, PartialEq, Eq, Debug)] +pub enum RenderOption { + NoEdgeLabels, + NoNodeLabels, + NoEdgeStyles, + NoNodeStyles, + + Fontname(String), + DarkTheme, +} + +/// Renders directed graph `g` into the writer `w` in DOT syntax. +/// (Simple wrapper around `render_opts` that passes a default set of options.) +pub fn render<'a, N, E, G, W>(g: &'a G, w: &mut W) -> io::Result<()> +where + N: Clone + 'a, + E: Clone + 'a, + G: Labeller<'a, Node = N, Edge = E> + GraphWalk<'a, Node = N, Edge = E>, + W: Write, +{ + render_opts(g, w, &[]) +} + +/// Renders directed graph `g` into the writer `w` in DOT syntax. +/// (Main entry point for the library.) +pub fn render_opts<'a, N, E, G, W>(g: &'a G, w: &mut W, options: &[RenderOption]) -> io::Result<()> +where + N: Clone + 'a, + E: Clone + 'a, + G: Labeller<'a, Node = N, Edge = E> + GraphWalk<'a, Node = N, Edge = E>, + W: Write, +{ + writeln!(w, "digraph {} {{", g.graph_id().as_slice())?; + + // Global graph properties + let mut graph_attrs = Vec::new(); + let mut content_attrs = Vec::new(); + let font; + if let Some(fontname) = options.iter().find_map(|option| { + if let RenderOption::Fontname(fontname) = option { Some(fontname) } else { None } + }) { + font = format!(r#"fontname="{}""#, fontname); + graph_attrs.push(&font[..]); + content_attrs.push(&font[..]); + } + if options.contains(&RenderOption::DarkTheme) { + graph_attrs.push(r#"bgcolor="black""#); + graph_attrs.push(r#"fontcolor="white""#); + content_attrs.push(r#"color="white""#); + content_attrs.push(r#"fontcolor="white""#); + } + if !(graph_attrs.is_empty() && content_attrs.is_empty()) { + writeln!(w, r#" graph[{}];"#, graph_attrs.join(" "))?; + let content_attrs_str = content_attrs.join(" "); + writeln!(w, r#" node[{}];"#, content_attrs_str)?; + writeln!(w, r#" edge[{}];"#, content_attrs_str)?; + } + + let mut text = Vec::new(); + for n in g.nodes().iter() { + write!(w, " ")?; + let id = g.node_id(n); + + let escaped = &g.node_label(n).to_dot_string(); + + write!(text, "{}", id.as_slice()).unwrap(); + + if !options.contains(&RenderOption::NoNodeLabels) { + write!(text, "[label={}]", escaped).unwrap(); + } + + let style = g.node_style(n); + if !options.contains(&RenderOption::NoNodeStyles) && style != Style::None { + write!(text, "[style=\"{}\"]", style.as_slice()).unwrap(); + } + + if let Some(s) = g.node_shape(n) { + write!(text, "[shape={}]", &s.to_dot_string()).unwrap(); + } + + writeln!(text, ";").unwrap(); + w.write_all(&text)?; + + text.clear(); + } + + for e in g.edges().iter() { + let escaped_label = &g.edge_label(e).to_dot_string(); + write!(w, " ")?; + let source = g.source(e); + let target = g.target(e); + let source_id = g.node_id(&source); + let target_id = g.node_id(&target); + + write!(text, "{} -> {}", source_id.as_slice(), target_id.as_slice()).unwrap(); + + if !options.contains(&RenderOption::NoEdgeLabels) { + write!(text, "[label={}]", escaped_label).unwrap(); + } + + let style = g.edge_style(e); + if !options.contains(&RenderOption::NoEdgeStyles) && style != Style::None { + write!(text, "[style=\"{}\"]", style.as_slice()).unwrap(); + } + + writeln!(text, ";").unwrap(); + w.write_all(&text)?; + + text.clear(); + } + + writeln!(w, "}}") +} + +#[cfg(test)] +mod tests; |