fix: Allocate ports on root nodes (#1585)

Closes #1584 

Not having ports in the root nodes caused problems when querying
information about them, as shown in #1584.
This PR changes the behaviour to instead allocate the ports, and
validate that they are always disconnected.
This should help make the API more homogeneous.

hugr-core/src/hugr.rs

@@ -176,9 +176,7 @@ impl Hugr {
  let mut graph = MultiPortGraph::with_capacity(nodes, ports);
  let hierarchy = Hierarchy::new();
  let mut op_types = UnmanagedDenseMap::with_capacity(nodes);
- let root = graph.add_node(0, 0);
- // TODO: These extensions should be open in principle, but lets wait
- // until extensions can be inferred for open sets until changing this
+ let root = graph.add_node(root_node.input_count(), root_node.output_count());
  op_types[root] = root_node;
 
  Self {

hugr-core/src/hugr/validate.rs

@@ -166,11 +166,25 @@ impl<'a, 'b> ValidationContext<'a, 'b> {
  ))?;
  }
  // The Hugr can have only one root node.
+
+ for dir in Direction::BOTH {
+ // Check that we have the correct amount of ports and edges.
+ let num_ports = self.hugr.graph.num_ports(node.pg_index(), dir);
+ if num_ports != op_type.port_count(dir) {
+ return Err(ValidationError::WrongNumberOfPorts {
+ node,
+ optype: op_type.clone(),
+ actual: num_ports,
+ expected: op_type.port_count(dir),
+ dir,
+ });
+ }
+ }
+
  if node == self.hugr.root() {
- // The root node has no edges.
- if self.hugr.graph.num_outputs(node.pg_index())
- + self.hugr.graph.num_inputs(node.pg_index())
- != 0
+ // The root node cannot have connected edges
+ if self.hugr.all_linked_inputs(node).next().is_some()
+ || self.hugr.all_linked_outputs(node).next().is_some()
  {
  return Err(ValidationError::RootWithEdges { node });
  }
@@ -190,20 +204,6 @@ impl<'a, 'b> ValidationContext<'a, 'b> {
  allowed_children,
  });
  }
-
- for dir in Direction::BOTH {
- // Check that we have the correct amount of ports and edges.
- let num_ports = self.hugr.graph.num_ports(node.pg_index(), dir);
- if num_ports != op_type.port_count(dir) {
- return Err(ValidationError::WrongNumberOfPorts {
- node,
- optype: op_type.clone(),
- actual: num_ports,
- expected: op_type.port_count(dir),
- dir,
- });
- }
- }
  }
 
  // Thirdly that the node has correct children
@@ -602,10 +602,14 @@ impl<'a, 'b> ValidationContext<'a, 'b> {
  }
 
  // Check port connections.
- for dir in Direction::BOTH {
- for (i, port_index) in self.hugr.graph.ports(node.pg_index(), dir).enumerate() {
- let port = Port::new(dir, i);
- self.validate_port(node, port, port_index, op_type, var_decls)?;
+ //
+ // Root nodes are ignored, as they cannot have connected edges.
+ if node != self.hugr.root() {
+ for dir in Direction::BOTH {
+ for (i, port_index) in self.hugr.graph.ports(node.pg_index(), dir).enumerate() {
+ let port = Port::new(dir, i);
+ self.validate_port(node, port, port_index, op_type, var_decls)?;
+ }
  }
  }
 

hugr-core/src/hugr/validate/test.rs

@@ -25,7 +25,9 @@ use crate::types::{
  CustomType, FuncValueType, PolyFuncType, PolyFuncTypeRV, Signature, Type, TypeBound, TypeRV,
  TypeRow,
 };
-use crate::{const_extension_ids, test_file, type_row, Direction, IncomingPort, Node};
+use crate::{
+ const_extension_ids, test_file, type_row, Direction, IncomingPort, Node, OutgoingPort,
+};
 
 const NAT: Type = crate::extension::prelude::USIZE_T;
 
@@ -68,36 +70,44 @@ fn add_df_children(b: &mut Hugr, parent: Node, copies: usize) -> (Node, Node, No
 
 #[test]
 fn invalid_root() {
- let declare_op: OpType = ops::FuncDecl {
- name: "main".into(),
- signature: Default::default(),
- }
- .into();
-
- let mut b = Hugr::default();
+ let mut b = Hugr::new(LogicOp::Not);
  let root = b.root();
- assert_eq!(b.validate(&EMPTY_REG), Ok(()));
+ assert_eq!(b.validate(&PRELUDE_REGISTRY), Ok(()));
+
+ // Change the number of ports in the root
+ b.set_num_ports(root, 1, 0);
+ assert_matches!(
+ b.validate(&PRELUDE_REGISTRY),
+ Err(ValidationError::WrongNumberOfPorts { node, .. }) => assert_eq!(node, root)
+ );
+ b.set_num_ports(root, 2, 2);
+
+ // Connect it to itself
+ b.connect(root, 0, root, 0);
+ assert_matches!(
+ b.validate(&PRELUDE_REGISTRY),
+ Err(ValidationError::RootWithEdges { node, .. }) => assert_eq!(node, root)
+ );
+ b.disconnect(root, OutgoingPort::from(0));
 
  // Add another hierarchy root
- let other = b.add_node(ops::Module::new().into());
+ let module = b.add_node(ops::Module::new().into());
  assert_matches!(
- b.validate(&EMPTY_REG),
- Err(ValidationError::NoParent { node }) => assert_eq!(node, other)
+ b.validate(&PRELUDE_REGISTRY),
+ Err(ValidationError::NoParent { node }) => assert_eq!(node, module)
  );
- b.set_parent(other, root);
- b.replace_op(other, declare_op).unwrap();
- b.add_ports(other, Direction::Outgoing, 1);
- assert_eq!(b.validate(&EMPTY_REG), Ok(()));
 
  // Make the hugr root not a hierarchy root
- {
- let mut hugr = b.clone();
- hugr.root = other.pg_index();
- assert_matches!(
- hugr.validate(&EMPTY_REG),
- Err(ValidationError::RootNotRoot { node }) => assert_eq!(node, other)
- );
- }
+ b.set_parent(root, module);
+ assert_matches!(
+ b.validate(&PRELUDE_REGISTRY),
+ Err(ValidationError::RootNotRoot { node }) => assert_eq!(node, root)
+ );
+
+ // Fix the root
+ b.root = module.pg_index();
+ b.remove_node(root);
+ assert_eq!(b.validate(&PRELUDE_REGISTRY), Ok(()));
 }
 
 #[test]

hugr-core/src/hugr/views.rs

@@ -24,7 +24,7 @@ use itertools::{Itertools, MapInto};
 use portgraph::render::{DotFormat, MermaidFormat};
 use portgraph::{multiportgraph, LinkView, PortView};
 
-use super::internal::{HugrInternals, HugrMutInternals};
+use super::internal::HugrInternals;
 use super::{
  Hugr, HugrError, HugrMut, NodeMetadata, NodeMetadataMap, ValidationError, DEFAULT_OPTYPE,
 };
@@ -509,7 +509,6 @@ pub trait ExtractHugr: HugrView + Sized {
  let old_root = hugr.root();
  let new_root = hugr.insert_from_view(old_root, &self).new_root;
  hugr.set_root(new_root);
- hugr.set_num_ports(new_root, 0, 0);
  hugr.remove_node(old_root);
  hugr
  }

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

@@ -3,7 +3,7 @@ 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) CFG</td></tr></table>>]
+0 [shape=plain label=<<table border="1"><tr><td port="in0" align="text" colspan="1" cellpadding="1" >0: usize</td></tr><tr><td align="text" border="0" colspan="1">(0) CFG</td></tr><tr><td port="out0" align="text" colspan="1" cellpadding="1" >0: usize</td></tr></table>>]
 1 [shape=plain label=<<table border="1"><tr><td port="in0" align="text" colspan="1" cellpadding="1" border="0">0</td></tr><tr><td align="text" border="0" colspan="1">(1) ExitBlock</td></tr></table>>]
 2 [shape=plain label=<<table border="1"><tr><td port="in0" align="text" colspan="2" cellpadding="1" border="0">0</td></tr><tr><td align="text" border="0" colspan="2">(2) DataflowBlock</td></tr><tr><td port="out0" align="text" colspan="1" cellpadding="1" border="0">0</td><td port="out1" align="text" colspan="1" cellpadding="1" border="0">1</td></tr></table>>]
 2:out0 -> 6:in0 [style="dashed"]
@@ -44,4 +44,3 @@ hier8 [shape=plain label="8"]
 hier9 [shape=plain label="9"]
 hier10 [shape=plain label="10"]
 }
-

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

@@ -1,9 +1,9 @@
 ---
-source: hugr-core/views/tests.rs
+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) DFG</td></tr></table>>]
+0 [shape=plain label=<<table border="1"><tr><td port="in0" align="text" colspan="2" cellpadding="1" >0: qubit</td><td port="in1" align="text" colspan="2" cellpadding="1" >1: qubit</td></tr><tr><td align="text" border="0" colspan="4">(0) DFG</td></tr><tr><td port="out0" align="text" colspan="2" cellpadding="1" >0: qubit</td><td port="out1" align="text" colspan="2" cellpadding="1" >1: qubit</td></tr></table>>]
 1 [shape=plain label=<<table border="1"><tr><td align="text" border="0" colspan="2">(1) Input</td></tr><tr><td port="out0" align="text" colspan="1" cellpadding="1" >0: qubit</td><td port="out1" align="text" colspan="1" cellpadding="1" >1: qubit</td></tr></table>>]
 1:out0 -> 3:in0 [style=""]
 1:out1 -> 3:in1 [style=""]

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

@@ -3,7 +3,7 @@ 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) DFG</td></tr></table>>]
+0 [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">(0) DFG</td></tr><tr><td port="out0" align="text" colspan="1" cellpadding="1" >0: []+[]</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>>]