feat: Render function names in mermaid/dot (#1583)

Shows the function names when rendering a hugr.
This should come useful when working with bigger graphs like those
emitted by guppy.

```mermaid
graph LR
    subgraph 0 ["(0) FuncDefn: #quot;test#quot;"]
        direction LR
        1["(1) Input"]
        2["(2) Output"]
        1--"0:0<br>[]+[]"-->2
    end
```

hugr-core/src/builder.rs

@@ -282,6 +282,22 @@ pub(crate) mod test {
         dfg_builder.finish_prelude_hugr_with_outputs([i1]).unwrap()
     }
 
+    #[fixture]
+    pub(crate) fn simple_funcdef_hugr() -> Hugr {
+        let fn_builder =
+            FunctionBuilder::new("test", Signature::new(type_row![BIT], type_row![BIT])).unwrap();
+        let [i1] = fn_builder.input_wires_arr();
+        fn_builder.finish_prelude_hugr_with_outputs([i1]).unwrap()
+    }
+
+    #[fixture]
+    pub(crate) fn simple_module_hugr() -> Hugr {
+        let mut builder = ModuleBuilder::new();
+        let sig = Signature::new(type_row![BIT], type_row![BIT]);
+        builder.declare("test", sig.into()).unwrap();
+        builder.finish_prelude_hugr().unwrap()
+    }
+
     #[fixture]
     pub(crate) fn simple_cfg_hugr() -> Hugr {
         let mut cfg_builder =

hugr-core/src/hugr/views/render.rs

@@ -4,7 +4,7 @@
 use portgraph::render::{EdgeStyle, NodeStyle, PortStyle};
 use portgraph::{LinkView, NodeIndex, PortIndex, PortView};
 
-use crate::ops::NamedOp;
+use crate::ops::{NamedOp, OpType};
 use crate::types::EdgeKind;
 use crate::HugrView;
 
@@ -35,16 +35,24 @@ pub(super) fn node_style<H: HugrView + ?Sized>(
     h: &H,
     config: RenderConfig,
 ) -> Box<dyn FnMut(NodeIndex) -> NodeStyle + '_> {
+    fn node_name<H: HugrView + ?Sized>(h: &H, n: NodeIndex) -> String {
+        match h.get_optype(n.into()) {
+            OpType::FuncDecl(f) => format!("FuncDecl: \"{}\"", f.name),
+            OpType::FuncDefn(f) => format!("FuncDefn: \"{}\"", f.name),
+            op => op.name().to_string(),
+        }
+    }
+
     if config.node_indices {
         Box::new(move |n| {
             NodeStyle::Box(format!(
                 "({ni}) {name}",
                 ni = n.index(),
-                name = h.get_optype(n.into()).name()
+                name = node_name(h, n)
             ))
         })
     } else {
-        Box::new(move |n| NodeStyle::Box(h.get_optype(n.into()).name().to_string()))
+        Box::new(move |n| NodeStyle::Box(node_name(h, n)))
     }
 }
 

hugr-core/src/hugr/views/snapshots/hugr_core__hugr__views__tests__dot_func.snap

@@ -0,0 +1,15 @@
+---
+source: hugr-core/src/hugr/views/tests.rs
+expression: h.dot_string()
+---
+digraph {
+0 [shape=plain label=<<table border="1"><tr><td align="text" border="0" colspan="1">(0) FuncDefn: "test"</td></tr><tr><td port="out0" align="text" colspan="1" cellpadding="1" >0: [[]+[]] -&gt; [[]][[]+[]]</td></tr></table>>]
+1 [shape=plain label=<<table border="1"><tr><td align="text" border="0" colspan="1">(1) Input</td></tr><tr><td port="out0" align="text" colspan="1" cellpadding="1" >0: []+[]</td></tr></table>>]
+1:out0 -> 2:in0 [style=""]
+2 [shape=plain label=<<table border="1"><tr><td port="in0" align="text" colspan="1" cellpadding="1" >0: []+[]</td></tr><tr><td align="text" border="0" colspan="1">(2) Output</td></tr></table>>]
+hier0 [shape=plain label="0"]
+hier0 -> hier1  [style = "dashed"] 
+hier0 -> hier2  [style = "dashed"] 
+hier1 [shape=plain label="1"]
+hier2 [shape=plain label="2"]
+}

hugr-core/src/hugr/views/snapshots/hugr_core__hugr__views__tests__dot_module.snap

@@ -0,0 +1,11 @@
+---
+source: hugr-core/src/hugr/views/tests.rs
+expression: h.dot_string()
+---
+digraph {
+0 [shape=plain label=<<table border="1"><tr><td align="text" border="0" colspan="1">(0) Module</td></tr></table>>]
+1 [shape=plain label=<<table border="1"><tr><td align="text" border="0" colspan="1">(1) FuncDecl: "test"</td></tr><tr><td port="out0" align="text" colspan="1" cellpadding="1" >0: [[]+[]] -&gt; [[]][[]+[]]</td></tr></table>>]
+hier0 [shape=plain label="0"]
+hier0 -> hier1  [style = "dashed"] 
+hier1 [shape=plain label="1"]
+}

hugr-core/src/hugr/views/snapshots/hugr_core__hugr__views__tests__mmd_func.snap

@@ -0,0 +1,11 @@
+---
+source: hugr-core/src/hugr/views/tests.rs
+expression: h.mermaid_string()
+---
+graph LR
+    subgraph 0 ["(0) FuncDefn: #quot;test#quot;"]
+        direction LR
+        1["(1) Input"]
+        2["(2) Output"]
+        1--"0:0<br>[]+[]"-->2
+    end

hugr-core/src/hugr/views/snapshots/hugr_core__hugr__views__tests__mmd_module.snap

@@ -0,0 +1,9 @@
+---
+source: hugr-core/src/hugr/views/tests.rs
+expression: h.mermaid_string()
+---
+graph LR
+    subgraph 0 ["(0) Module"]
+        direction LR
+        1["(1) FuncDecl: #quot;test#quot;"]
+    end

hugr-core/src/hugr/views/tests.rs

@@ -71,6 +71,8 @@ fn node_connections(
 #[case::dfg("dot_dfg", sample_hugr().0)]
 #[case::cfg("dot_cfg", crate::builder::test::simple_cfg_hugr())]
 #[case::empty_dfg("dot_empty_dfg", crate::builder::test::simple_dfg_hugr())]
+#[case::func("dot_func", crate::builder::test::simple_funcdef_hugr())]
+#[case::module("dot_module", crate::builder::test::simple_module_hugr())]
 #[cfg_attr(miri, ignore)] // Opening files is not supported in (isolated) miri
 fn dot_string(#[case] test_name: &str, #[case] h: Hugr) {
     insta::assert_snapshot!(test_name, h.dot_string());
@@ -84,6 +86,8 @@ fn dot_string(#[case] test_name: &str, #[case] h: Hugr) {
 #[case::dfg("mmd_dfg", sample_hugr().0)]
 #[case::cfg("mmd_cfg", crate::builder::test::simple_cfg_hugr())]
 #[case::empty_dfg("mmd_empty_dfg", crate::builder::test::simple_dfg_hugr())]
+#[case::func("mmd_func", crate::builder::test::simple_funcdef_hugr())]
+#[case::module("mmd_module", crate::builder::test::simple_module_hugr())]
 #[cfg_attr(miri, ignore)] // Opening files is not supported in (isolated) miri
 fn mermaid_string(#[case] test_name: &str, #[case] h: Hugr) {
     insta::assert_snapshot!(test_name, h.mermaid_string());

hugr-core/src/types/poly_func.rs

@@ -1,5 +1,7 @@
 //! Polymorphic Function Types
 
+use itertools::Itertools;
+
 use crate::extension::{ExtensionRegistry, SignatureError};
 #[cfg(test)]
 use {
@@ -22,11 +24,7 @@ use super::{signature::FuncTypeBase, MaybeRV, NoRV, RowVariable};
     Clone, PartialEq, Debug, Eq, Hash, derive_more::Display, serde::Serialize, serde::Deserialize,
 )]
 #[cfg_attr(test, derive(Arbitrary), proptest(params = "RecursionDepth"))]
-#[display(
-    "forall {}. {}",
-    "params.iter().map(ToString::to_string).join(\" \")",
-    "body"
-)]
+#[display("{}{body}", self.display_params())]
 pub struct PolyFuncTypeBase<RV: MaybeRV> {
     /// The declared type parameters, i.e., these must be instantiated with
     /// the same number of [TypeArg]s before the function can be called. This
@@ -136,6 +134,17 @@ impl<RV: MaybeRV> PolyFuncTypeBase<RV> {
         // TODO https://github.com/CQCL/hugr/issues/624 validate TypeParams declared here, too
         self.body.validate(reg, &self.params)
     }
+
+    /// Helper function for the Display implementation
+    fn display_params(&self) -> String {
+        if self.params.is_empty() {
+            return String::new();
+        }
+        format!(
+            "forall {}. ",
+            self.params.iter().map(ToString::to_string).join(" ")
+        )
+    }
 }
 
 #[cfg(test)]