[Backport] Move visualize overloads to package extension; bump to v0.21.2 (#369)

## Summary

Backport of #367 onto the new `release-0.21` branch.

Replaces the in-source `visualize(::AbstractITensorNetwork, ...)` method
(in `src/abstractitensornetwork.jl`) and the two type-piracy methods on
`AbstractNamedGraph` / `AbstractDataGraph` (in `src/visualize.jl`) with
a single `ITensorNetworksITensorVisualizationBaseExt` package extension
that overloads `visualize(::AbstractITensorNetwork, ...)` only. The
type-piracy methods migrate upstream:

- `NamedGraphs.jl` v0.11.1
([#166](ITensor/NamedGraphs.jl#166)) adds the
`AbstractNamedGraph` overload via its own
`NamedGraphsITensorVisualizationBaseExt`.
- `DataGraphs.jl` v0.4.1
([#119](ITensor/DataGraphs.jl#119)) adds the
`AbstractDataGraph` overload via
`DataGraphsITensorVisualizationBaseExt`.

## Motivation for backporting

Once NamedGraphs v0.11.1 and DataGraphs v0.4.1 register, any user on
legacy ITensorNetworks v0.21.x alongside the new NamedGraphs/DataGraphs
would hit method-overwrite warnings on the two type-pirated `visualize`
methods. v0.22 may take a while to ship (its prerelease accumulator is
still receiving changes), so we publish a v0.21.2 patch carrying the
equivalent fix.

## Changes

- Adds `ext/ITensorNetworksITensorVisualizationBaseExt/`.
- Removes `src/visualize.jl` (and its `include` from
`src/ITensorNetworks.jl`).
- Removes the `visualize(::AbstractITensorNetwork, ...)` block from
`src/abstractitensornetwork.jl`.
- Adds `ITensorVisualizationBase` to `[weakdeps]` / `[extensions]` /
`[compat]`.
- Bumps `[compat]` floors: `NamedGraphs = "0.11.1"`, `DataGraphs =
"0.4.1"`.
- Bumps package version `0.21.1` → `0.21.2`.

## Release-branch workflow

This is the first PR against the new `release-0.21` branch, modeled on
Julia's `release-X.Y` convention (simplified — no
`backports-release-X.Y` staging tier, since we expect only 1–2 backports
before v0.22 ships).

After merge, registration needs to be triggered manually via a
`/register <merge-sha>` commit comment on the merge commit (the
`Registrator.yml` workflow's `push` trigger only fires on
`main`/`master` by default; the `issue_comment` path uses `force=true`
and works regardless of branch).

## Status

CI will be red until NamedGraphs v0.11.1 and DataGraphs v0.4.1 actually
land in the registry. Opening the PR now mostly for tracking.

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: mtfishman

Project.toml

@@ -1,6 +1,6 @@
 name = "ITensorNetworks"
 uuid = "2919e153-833c-4bdc-8836-1ea460a35fc7"
-version = "0.21.1"
+version = "0.21.2"
 authors = ["Matthew Fishman <mfishman@flatironinstitute.org>, Joseph Tindall <jtindall@flatironinstitute.org> and contributors"]
 
 [workspace]
@@ -38,10 +38,12 @@ TimerOutputs = "a759f4b9-e2f1-59dc-863e-4aeb61b1ea8f"
 TupleTools = "9d95972d-f1c8-5527-a6e0-b4b365fa01f6"
 
 [weakdeps]
+ITensorVisualizationBase = "cd2553d2-8bef-4d93-8a38-c62f17d5ad23"
 OMEinsumContractionOrders = "6f22d1fd-8eed-4bb7-9776-e7d684900715"
 TensorOperations = "6aa20fa7-93e2-5fca-9bc0-fbd0db3c71a2"
 
 [extensions]
+ITensorNetworksITensorVisualizationBaseExt = "ITensorVisualizationBase"
 ITensorNetworksOMEinsumContractionOrdersExt = "OMEinsumContractionOrders"
 ITensorNetworksTensorOperationsExt = "TensorOperations"
 
@@ -52,18 +54,19 @@ Adapt = "4"
 Combinatorics = "1"
 Compat = "3, 4"
 ConstructionBase = "1.6"
-DataGraphs = "0.4"
+DataGraphs = "0.4.1"
 Dictionaries = "0.4"
 Distributions = "0.25.86"
 DocStringExtensions = "0.9"
 Graphs = "1.8"
+ITensorVisualizationBase = "0.1"
 ITensors = "0.7, 0.8, 0.9"
 IsApprox = "0.1, 1, 2"
 IterTools = "1.4"
 KrylovKit = "0.6, 0.7, 0.8, 0.9, 0.10"
 MacroTools = "0.5"
 NDTensors = "0.3, 0.4"
-NamedGraphs = "0.11"
+NamedGraphs = "0.11.1"
 OMEinsumContractionOrders = "0.8.3, 0.9, 1"
 SerializedElementArrays = "0.1"
 SimpleTraits = "0.9"

ext/ITensorNetworksITensorVisualizationBaseExt/ITensorNetworksITensorVisualizationBaseExt.jl

@@ -0,0 +1,22 @@
+module ITensorNetworksITensorVisualizationBaseExt
+
+using Graphs: vertices
+using ITensorNetworks: AbstractITensorNetwork
+using ITensorVisualizationBase: ITensorVisualizationBase
+
+function ITensorVisualizationBase.visualize(
+        tn::AbstractITensorNetwork,
+        args...;
+        vertex_labels_prefix = nothing,
+        vertex_labels = nothing,
+        kwargs...
+    )
+    if !isnothing(vertex_labels_prefix)
+        vertex_labels = [vertex_labels_prefix * string(v) for v in vertices(tn)]
+    end
+    return ITensorVisualizationBase.visualize(
+        [tn[v] for v in vertices(tn)], args...; vertex_labels, kwargs...
+    )
+end
+
+end

src/ITensorNetworks.jl

@@ -2,7 +2,6 @@ module ITensorNetworks
 
 include("lib/BaseExtensions/src/BaseExtensions.jl")
 include("lib/ITensorsExtensions/src/ITensorsExtensions.jl")
-include("visualize.jl")
 include("abstractindsnetwork.jl")
 include("indextags.jl")
 include("indsnetwork.jl")

src/abstractitensornetwork.jl

@@ -791,24 +791,6 @@ end
 
 Base.show(io::IO, graph::AbstractITensorNetwork) = show(io, MIME"text/plain"(), graph)
 
-# TODO: Move to an `ITensorNetworksVisualizationInterfaceExt`
-# package extension (and define a `VisualizationInterface` package
-# based on `ITensorVisualizationCore`.).
-using ITensors.ITensorVisualizationCore: ITensorVisualizationCore, visualize
-function ITensorVisualizationCore.visualize(
-        tn::AbstractITensorNetwork,
-        args...;
-        vertex_labels_prefix = nothing,
-        vertex_labels = nothing,
-        kwargs...
-    )
-    if !isnothing(vertex_labels_prefix)
-        vertex_labels = [vertex_labels_prefix * string(v) for v in vertices(tn)]
-    end
-    # TODO: Use `tokenize_vertex`.
-    return visualize([tn[v] for v in vertices(tn)], args...; vertex_labels, kwargs...)
-end
-
 #
 # Link dimensions
 #

src/visualize.jl

@@ -12,6 +12,7 @@ GraphsFlows = "06909019-6f44-4949-96fc-b9d9aaa02889"
 ITensorMPS = "0d1a4710-d33b-49a5-8f18-73bdf49b47e2"
 ITensorNetworks = "2919e153-833c-4bdc-8836-1ea460a35fc7"
 ITensorPkgSkeleton = "3d388ab1-018a-49f4-ae50-18094d5f71ea"
+ITensorVisualizationBase = "cd2553d2-8bef-4d93-8a38-c62f17d5ad23"
 ITensors = "9136182c-28ba-11e9-034c-db9fb085ebd5"
 KrylovKit = "0b1a1467-8014-51b9-945f-bf0ae24f4b77"
 LinearAlgebra = "37e2e46d-f89d-539d-b4ee-838fcccc9c8e"
@@ -38,7 +39,7 @@ AbstractTrees = "0.4.5"
 Adapt = "4.3"
 Aqua = "0.8.11"
 Compat = "4.16"
-DataGraphs = "0.4"
+DataGraphs = "0.4.1"
 Dictionaries = "0.4.4"
 Distributions = "0.25.118"
 Glob = "1.3.1"
@@ -47,12 +48,13 @@ GraphsFlows = "0.1.1"
 ITensorMPS = "0.3.6, 0.4"
 ITensorNetworks = "0.21"
 ITensorPkgSkeleton = "0.3.42"
+ITensorVisualizationBase = "0.1"
 ITensors = "0.7, 0.8, 0.9"
 KrylovKit = "0.8, 0.9, 0.10"
 LinearAlgebra = "1.10"
 Metis = "1.5"
 NDTensors = "0.3, 0.4"
-NamedGraphs = "0.11"
+NamedGraphs = "0.11.1"
 OMEinsumContractionOrders = "0.9.5, 1"
 Pkg = "1.10"
 Random = "1.10"

test/Project.toml

@@ -0,0 +1,12 @@
+using ITensorNetworks: AbstractITensorNetwork, ITensorNetwork
+using ITensorVisualizationBase: ITensorVisualizationBase
+using ITensors: ITensor, Index
+using Test: @test, @testset
+
+@testset "ITensorNetworksITensorVisualizationBaseExt" begin
+    i, j, k = Index(2, "i"), Index(2, "j"), Index(2, "k")
+    tn = ITensorNetwork([ITensor(i, j), ITensor(j, k)])
+    @test hasmethod(ITensorVisualizationBase.visualize, Tuple{AbstractITensorNetwork})
+    @test isnothing(ITensorVisualizationBase.visualize(tn))
+    @test isnothing(ITensorVisualizationBase.visualize(tn; vertex_labels_prefix = "v"))
+end