refactor(metadata)!: Migrate all metadata keys onto the new metadata traits by maximilianruesch · Pull Request #1328 · Quantinuum/tket2

maximilianruesch · 2025-12-19T14:34:21Z

Migrates all metadata keys (that I know of) in tket to use the new metadata traits introduced in HUGR, and unifies them to be in one file. This includes some debugging metadata, unitary flags, etc. Finally, some trivial fixes / simplifications are added that come as a convenience of the new metadata system.

I would still argue that this is a refactor, even though a breaking refactor seems contradictional.

Related to Quantinuum/guppylang#1378

BREAKING CHANGE: Renamed the "unitary" key to contain the TKET prefix as is standard with all other metadata keys.

codecov · 2025-12-19T14:38:26Z

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 79.59%. Comparing base (7487e3a) to head (f48f09b).
⚠️ Report is 1 commits behind head on main.

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@@            Coverage Diff             @@
##             main    #1328      +/-   ##
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==========================================
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- Misses       3168     3203      +35     
- Partials      979      981       +2

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ss2165 · 2026-01-14T10:31:46Z

Ensure the "BREAKING CHANGE: " notice is always at the bottom of the description

ss2165 · 2026-01-14T10:36:51Z

tket/src/serialize/pytket/decoder.rs

+            .set_metadata::<metadata::Phase>(node, &serialcirc.phase);
        dfg.hugr_mut()
-            .set_metadata_any(node, METADATA_Q_REGISTERS, json!(serialcirc.qubits));
+            .set_metadata::<metadata::QubitRegisters>(node, serialcirc.qubits.clone()); // TODO Do we find something better than clone?


not clear what this todo means

The question is whether we find something that avoids the clone, whether it is inevitable, or whether it should be cheap enough to remain. Might be the last case if it is a small vec of ints.

Outcome: The clone here is not avoidable without major changes to the function interface, and it seems to be cheap. It shall be fine.

ss2165 · 2026-01-14T10:40:02Z

tket/src/serialize/pytket/tests.rs

        hugr.entrypoint(),
-        METADATA_INPUT_PARAMETERS,
-        serde_json::json!(["alpha", "beta"]),
+        vec![String::from("alpha"), String::from("beta")],


nit: "".to_string() is standard and a bit more concise

ss2165 · 2026-01-14T10:42:02Z

tket/src/metadata.rs

@@ -0,0 +1,75 @@
+//! (Incomplete) Collection of metadata keys used throughout tket.


what's missing?

Seems to be an oversight, the collection was previously incomplete, but now every key should be in here.

ss2165 · 2026-01-14T10:42:21Z

tket/src/metadata.rs

+
+/// Metadata key for the number of qubits that a HUGR node expects to be required for execution.
+///
+/// This value is only valid when set at the entrypoint function node. TODO discuss this


Outcome: The comment will be removed. We will not enforce any constraints.

ss2165 · 2026-01-14T10:42:51Z

tket/src/metadata.rs

+#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct MaxQubits;
+impl Metadata for MaxQubits {
+    const KEY: &'static str = "TKET.expected_qubits"; // TODO think about this name really hard


this doesn't line up with the name of the struct or what is used in released guppy

Also a source of discussion, since we want to rename the key. We now have yet another opportunity to rename it, before we use it in tket somewhere.

Alternatively, we could decide that we only want to introduce the key when we actually use it in tket, but we should decide on a name pretty soon imo.

Outcome: Guppy uses tket.hint.max_qubits, so we will use that.

ss2165 · 2026-01-14T10:44:58Z

tket/src/metadata.rs

+pub struct MaxQubits;
+impl Metadata for MaxQubits {
+    const KEY: &'static str = "TKET.expected_qubits"; // TODO think about this name really hard
+    type Type<'hugr> = u32;


is the 'hugr lifetime annotation required if it is not used?

Yes, since the trait specifies Type to have a generic lifetime parameter and that must be specified as far as I know, even if unused. It can have any name, but for consistency I chose 'hugr

ss2165 · 2026-01-14T10:45:17Z

tket/src/metadata.rs

+
+/// Metadata key for flagging unitarity constraints on a HUGR node
+///
+/// See crate::modifier::ModifierFlags TODO discuss this


Leftover, will be removed.

tket/src/metadata.rs

ss2165 · 2026-01-14T10:46:16Z

tket/src/metadata.rs

+    type Type<'hugr> = u8;
+}
+
+// Metadata keys migrated from TKET1


Suggested change

// Metadata keys migrated from TKET1

// Metadata keys used for TKET1 compatibility

hugrbot · 2026-01-14T11:31:51Z

This PR contains breaking changes to the public Rust API.

cargo-semver-checks summary

    Building tket v0.16.0 (current)
     Built [  45.587s] (current)
   Parsing tket v0.16.0 (current)
    Parsed [   0.105s] (current)
  Building tket v0.16.0 (baseline)
     Built [  43.919s] (baseline)
   Parsing tket v0.16.0 (baseline)
    Parsed [   0.086s] (baseline)
  Checking tket v0.16.0 -> v0.16.0 (assume minor change)
   Checked [   0.081s] 159 checks: 158 pass, 1 fail, 0 warn, 41 skip

--- failure pub_module_level_const_missing: pub module-level const is missing ---

Description:
A public const is missing or renamed
      ref: https://doc.rust-lang.org/cargo/reference/semver.html#item-remove
     impl: https://github.com/obi1kenobi/cargo-semver-checks/tree/v0.45.0/src/lints/pub_module_level_const_missing.ron

Failed in:
METADATA_Q_REGISTERS in file /home/runner/work/tket2/tket2/BASELINE_BRANCH/tket/src/serialize/pytket.rs:52
METADATA_INPUT_PARAMETERS in file /home/runner/work/tket2/tket2/BASELINE_BRANCH/tket/src/serialize/pytket.rs:58
METADATA_REWRITES in file /home/runner/work/tket2/tket2/BASELINE_BRANCH/tket/src/rewrite/trace.rs:14
METADATA_PREFIX in file /home/runner/work/tket2/tket2/BASELINE_BRANCH/tket/src/serialize/pytket.rs:48
METADATA_OPGROUP in file /home/runner/work/tket2/tket2/BASELINE_BRANCH/tket/src/serialize/pytket.rs:56
METADATA_B_REGISTERS in file /home/runner/work/tket2/tket2/BASELINE_BRANCH/tket/src/serialize/pytket.rs:54
METADATA_PHASE in file /home/runner/work/tket2/tket2/BASELINE_BRANCH/tket/src/serialize/pytket.rs:50

   Summary semver requires new major version: 1 major and 0 minor checks failed
  Finished [  91.863s] tket
  Building tket-qsystem v0.22.0 (current)
     Built [  45.784s] (current)
   Parsing tket-qsystem v0.22.0 (current)
    Parsed [   0.029s] (current)
  Building tket-qsystem v0.22.0 (baseline)
     Built [  45.631s] (baseline)
   Parsing tket-qsystem v0.22.0 (baseline)
    Parsed [   0.029s] (baseline)
  Checking tket-qsystem v0.22.0 -> v0.22.0 (assume minor change)
   Checked [   0.047s] 159 checks: 159 pass, 41 skip
   Summary no semver update required
  Finished [  93.583s] tket-qsystem

## 🤖 New release * `tket`: 0.16.0 -> 0.17.0 (✓ API compatible changes) * `tket-qsystem`: 0.22.0 -> 0.23.0 (✓ API compatible changes) <details><summary>Changelog</summary> ## `tket` <blockquote> ## [0.17.0](tket-v0.16.0...tket-v0.17.0) - 2026-02-02 ### Bug Fixes - *(encoded-circ)* Track unsupported wires between input and output ([#1224](#1224)) - Multiple fixes to the pytket encoder ([#1226](#1226)) - Don't use opgroup in pytket barrier encoding ([#1251](#1251)) - guppy_to_circuit always returns num_operations = 0 ([#1200](#1200)) - *(pytket-decoder)* Avoid QAllocating and immediately freeing qubits ([#1256](#1256)) - Encoding of opaque subgraphs with no associated qubit/bit ([#1295](#1295)) - [**breaking**] Don't rely on command params for pytket barriers ([#1298](#1298)) - Track output qubits in CircuitInfo ([#1304](#1304)) - Wrongly reused qubit IDs in pytket encoding ([#1358](#1358)) ### New Features - Deprecate local find_tuple_unpack rewrite ([#1188](#1188)) - Add CopyableExpressionAST ([#1209](#1209)) - `NormalizeGuppy` pass to simplify generated structure ([#1220](#1220)) - [**breaking**] pytket EncodedCircuit struct for in-place pytket optimisation ([#1211](#1211)) - [**breaking**] Interval is independent of resource IDs and scope position ([#1205](#1205)) - Don't translate usizes to pytket ([#1241](#1241)) - BorrowSquashPass to elide redundant borrow/return ops ([#1159](#1159)) - [**breaking**] Bump hugr to 0.25.0 ([#1325](#1325)) - Remove order edges in NormalizeGuppy pass ([#1326](#1326)) - [**breaking**] Remove deprecated unpack tuple pass ([#1387](#1387)) ### Refactor - Remove contain_qubits, use TypeUnpacker ([#1283](#1283)) - [**breaking**] Replace Subcircuit with SiblingSubgraph ([#1288](#1288)) - *(metadata)* [**breaking**] Migrate all metadata keys onto the new metadata traits ([#1328](#1328)) </blockquote> ## `tket-qsystem` <blockquote> ## [0.23.0](tket-qsystem-v0.22.0...tket-qsystem-v0.23.0) - 2026-02-02 ### Bug Fixes - [**breaking**] Don't rely on command params for pytket barriers ([#1298](#1298)) - Wrongly reused qubit IDs in pytket encoding ([#1358](#1358)) ### New Features - `NormalizeGuppy` pass to simplify generated structure ([#1220](#1220)) - Allow running arbitrary serializable pytket passes on hugrs ([#1266](#1266)) - BorrowSquashPass to elide redundant borrow/return ops ([#1159](#1159)) - [**breaking**] Bump hugr to 0.25.0 ([#1325](#1325)) - Remove order edges in NormalizeGuppy pass ([#1326](#1326)) - hide new public funcs introduced by linearization ([#1333](#1333)) ### Testing - regenerate guppy_opt examples, and count gates ([#1249](#1249)) - run pytket on guppy_opt tests, measure (very limited) success ([#1250](#1250)) </blockquote> </details> --- This PR was generated with [release-plz](https://github.com/release-plz/release-plz/).

aborgna-q and others added 24 commits December 16, 2025 10:29

feat! Bump hugr to 0.25.0

9fef0b6

drive-by: Fix justfile setup

4060c73

Update envelope / read errors

9ae7961

Update metadata method calls

ee01fea

SiblingSubgraph requires RootChecked

350057b

Extension definitions return an Arc rather than Weak<Extension>

d572aa4

Replace deprecated ReplaceTypes::replace_op

ba45b19

inkwell breaking changes

7944c50

downgrade non-weak extensions

91ead38

pyo3 breaking changes

a193513

More deprecated fns

45d5bc3

More changes/deprecations

4844b87

drop op in replacer

ecea580

rollback one of the replaceTypes fixes

13a21b4

fix unwrap

b8210fa

one fewer deprecated call

76e0059

last deprecated call

2070eb5

Update snapshots

31e2338

Add metadata module and first key

5048978

Migrate a bunch of keys most of the way

0f26c40

Migrate tracing

3b3aee6

Fix rewrite traces

5826aa6

Fix rewrite traces (yet again)

68c4a0c

Fix rewrite traces (yet again * 2)

2d3fe8e

maximilianruesch mentioned this pull request Dec 19, 2025

feat!: Add qubit hints on Guppy functions, allowing elision when building emulators Quantinuum/guppylang#1378

Merged

aborgna-q force-pushed the ab/bump-hugr-0.25 branch 3 times, most recently from 3b4efbe to c7a2221 Compare December 30, 2025 16:59

Base automatically changed from ab/bump-hugr-0.25 to main December 30, 2025 17:45

maximilianruesch added 2 commits January 13, 2026 10:18

Merge branch 'main' into mr/feat/migrate-metadata

ad817c5

Merge branch 'main' into mr/feat/migrate-metadata

3dee032

maximilianruesch marked this pull request as ready for review January 13, 2026 11:09

maximilianruesch requested a review from a team as a code owner January 13, 2026 11:09

maximilianruesch requested a review from ss2165 January 13, 2026 11:09

ss2165 reviewed Jan 14, 2026

View reviewed changes

maximilianruesch added 2 commits January 14, 2026 11:22

Trivial comment changes

6808b66

Use canonical to_string

bee72cb

maximilianruesch mentioned this pull request Jan 14, 2026

Rename metadata key prefix to its lowercase equivalent #1355

Open

maximilianruesch added 3 commits January 15, 2026 13:32

Remove unused todos

8ffddbc

Use max_qubits hint key from guppylang

6683f45

Merge branch 'main' into mr/feat/migrate-metadata

f48f09b

maximilianruesch requested a review from ss2165 January 15, 2026 13:43

ss2165 approved these changes Jan 15, 2026

View reviewed changes

maximilianruesch added this pull request to the merge queue Jan 15, 2026

Merged via the queue into main with commit 60ce5e2 Jan 15, 2026
24 checks passed

maximilianruesch deleted the mr/feat/migrate-metadata branch January 15, 2026 14:37

hugrbot mentioned this pull request Jan 15, 2026

chore: release #1189

Merged

hugrbot mentioned this pull request Feb 5, 2026

chore: release #1394

Merged

		@@ -0,0 +1,75 @@
		//! (Incomplete) Collection of metadata keys used throughout tket.

	// Metadata keys migrated from TKET1
	// Metadata keys used for TKET1 compatibility

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