Replace toml with tomllib & tomli (#857)

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------------------------------------------------------------------------------------------------------------

**Context:**
Prefer `tomlkit` over `toml` for building Lightning wheels, and choose
`tomli` and `tomllib` over `toml` when installing the package.

**Description of the Change:**

**Benefits:**
- `tomli` and `tomllib` (for python > 3.10) provides a read-only,
lightweight and fast toml parser compare to `toml`
- `tomlkit` gets regular updates and provides support for all the toml
updates and new standards. `toml` [hasn't been updated since Oct
2020](https://pypi.org/project/toml/).
**Possible Drawbacks:**

**Related GitHub Issues:**
[sc-71707]

---------

Co-authored-by: ringo-but-quantum <github-ringo-but-quantum@xanadu.ai>
Co-authored-by: Amintor Dusko <87949283+AmintorDusko@users.noreply.github.com>

.github/CHANGELOG.md

@@ -15,6 +15,9 @@
 
 ### Improvements
 
+* Prefer `tomlkit` over `toml` for building Lightning wheels, and choose `tomli` and `tomllib` over `toml` when installing the package.
+  [(#857)](https://github.com/PennyLaneAI/pennylane-lightning/pull/857)
+
 * Update GitHub actions in response to a high-severity vulnerability.
   [(#887)](https://github.com/PennyLaneAI/pennylane-lightning/pull/887)
 

.github/workflows/wheel_linux_aarch64.yml

@@ -125,7 +125,7 @@ jobs:
           cp -rf ${{ github.workspace }}/Kokkos_install/${{ matrix.exec_model }}/* Kokkos/
 
       - name: Install dependencies
-        run: python -m pip install cibuildwheel~=2.16.0 toml
+        run: python -m pip install cibuildwheel~=2.16.0 tomlkit
 
       - name: Configure pyproject.toml file
         run: PL_BACKEND="${{ matrix.pl_backend }}" python scripts/configure_pyproject_toml.py

.github/workflows/wheel_linux_aarch64_cuda.yml

@@ -49,7 +49,7 @@ jobs:
         uses: actions/checkout@v4
 
       - name: Install cibuildwheel
-        run: python -m pip install cibuildwheel~=2.16.0 toml
+        run: python -m pip install cibuildwheel~=2.16.0 tomlkit
 
       - name: Configure pyproject.toml file
         run: PL_BACKEND="${{ matrix.pl_backend }}" python scripts/configure_pyproject_toml.py

.github/workflows/wheel_linux_ppc64le.yml

@@ -124,7 +124,7 @@ jobs:
           cp -rf ${{ github.workspace }}/Kokkos_install/${{ matrix.exec_model }}/* Kokkos/
 
       - name: Install dependencies
-        run: python -m pip install cibuildwheel~=2.16.0 toml
+        run: python -m pip install cibuildwheel~=2.16.0 tomlkit
 
       - uses: docker/setup-qemu-action@v3
         name: Set up QEMU

.github/workflows/wheel_linux_x86_64.yml

@@ -141,7 +141,7 @@ jobs:
           dnf update -y && dnf install -y podman
 
       - name: Install dependencies
-        run: python3.10 -m pip install cibuildwheel~=2.16.0 toml
+        run: python3.10 -m pip install cibuildwheel~=2.16.0 tomlkit
 
       - name: Configure pyproject.toml file
         run: PL_BACKEND="${{ matrix.pl_backend }}" python3.10 scripts/configure_pyproject_toml.py

.github/workflows/wheel_linux_x86_64_cuda.yml

@@ -68,7 +68,7 @@ jobs:
           dnf update -y && dnf install -y podman
 
       - name: Install dependencies
-        run: python3.10 -m pip install cibuildwheel~=2.16.0 toml
+        run: python3.10 -m pip install cibuildwheel~=2.16.0 tomlkit
 
       - name: Configure pyproject.toml file
         run: PL_BACKEND="${{ matrix.pl_backend }}" python3.10 scripts/configure_pyproject_toml.py

.github/workflows/wheel_macos_arm64.yml

@@ -81,7 +81,7 @@ jobs:
           python-version: '3.10'
 
       - name: Install dependencies
-        run: python -m pip install cibuildwheel~=2.16.0 toml
+        run: python -m pip install cibuildwheel~=2.16.0 tomlkit
 
       - name: Configure pyproject.toml file
         run: PL_BACKEND="${{ matrix.pl_backend }}" python scripts/configure_pyproject_toml.py

.github/workflows/wheel_macos_x86_64.yml

@@ -130,7 +130,7 @@ jobs:
           python-version: '3.10'
 
       - name: Install dependencies
-        run: python -m pip install cibuildwheel~=2.16.0 toml
+        run: python -m pip install cibuildwheel~=2.16.0 tomlkit
 
       - name: Configure pyproject.toml file
         run: PL_BACKEND="${{ matrix.pl_backend }}" python scripts/configure_pyproject_toml.py

.github/workflows/wheel_noarch.yml

@@ -65,7 +65,7 @@ jobs:
       - name: Install dependencies
         if: ${{ matrix.pl_backend == 'lightning_qubit'}}
         run: |
-          python -m pip install toml
+          python -m pip install tomlkit
 
       - name: Configure pyproject.toml file
         if: ${{ matrix.pl_backend == 'lightning_qubit'}}

pennylane_lightning/core/_version.py

@@ -16,4 +16,4 @@
    Version number (major.minor.patch[-label])
 """
 
-__version__ = "0.39.0-dev7"
+__version__ = "0.39.0-dev8"

pyproject.toml

@@ -1,5 +1,5 @@
 [build-system]
-requires = [ "cmake~=3.24.0", "ninja; platform_system!='Windows'", "setuptools>=42", "toml",]
+requires = ["cmake~=3.24.0", "ninja; platform_system!='Windows'", "setuptools>=42", "tomli"]
 build-backend = "setuptools.build_meta"
 
 [project]
@@ -8,7 +8,7 @@ description = "PennyLane-Lightning plugin"
 readme = "README.rst"
 requires-python = ">=3.10"
 classifiers = [ "Development Status :: 4 - Beta", "Environment :: Console", "Intended Audience :: Science/Research", "License :: OSI Approved :: Apache Software License", "Natural Language :: English", "Operating System :: MacOS :: MacOS X", "Operating System :: Microsoft :: Windows", "Operating System :: POSIX", "Operating System :: POSIX :: Linux", "Programming Language :: Python", "Programming Language :: Python :: 3", "Programming Language :: Python :: 3 :: Only", "Programming Language :: Python :: 3.10", "Programming Language :: Python :: 3.11", "Programming Language :: Python :: 3.12", "Topic :: Scientific/Engineering :: Physics",]
-dependencies = [ "pennylane>=0.37",]
+dependencies = ["pennylane>=0.37"]
 dynamic = [ "version",]
 [[project.maintainers]]
 name = "Xanadu Quantum Technologies Inc."

scripts/configure_pyproject_toml.py

@@ -16,9 +16,10 @@
 """
 import argparse
 import os
+from importlib import import_module
+from importlib.util import find_spec
 from pathlib import Path
 
-import toml
 from backend_support import backend, device_name
 
 path_to_project = Path(__file__).parent.parent.absolute()
@@ -28,6 +29,19 @@
     version = f.readlines()[-1].split()[-1].strip("\"'")
 
 
+# ------------------------
+# Find the toml parser.
+# ------------------------
+has_toml = False
+toml_libs = ["tomlkit", "toml"]  # "tomllib" and "tomli" do not implement 'dump'.
+for pkg in toml_libs:
+    spec = find_spec(pkg)
+    if spec:
+        toml = import_module(pkg)
+        has_toml = True
+        break
+
+
 ########################################################################
 # Parsing arguments
 ########################################################################
@@ -57,7 +71,19 @@ def parse_args():
 
     pyproject_path = os.path.join(parsed_args.path, "pyproject.toml")
 
-    pyproject = toml.load(pyproject_path)
+    if not has_toml:
+        raise ImportError(
+            "A TOML parser is required to configure 'pyproject.toml'. "
+            f"We support any of the following TOML parsers: {toml_libs} "
+            "You can install tomlkit via `pip install tomlkit`."
+        )
+
+    try:
+        with open(pyproject_path, "rb") as f:
+            pyproject = toml.load(f)
+    except TypeError:
+        # To support toml and tomli APIs
+        pyproject = toml.load(pyproject_path)
 
     # ------------------------
     # Configure Build.
@@ -66,7 +92,7 @@ def parse_args():
         "cmake~=3.24.0",
         "ninja; platform_system!='Windows'",
         "setuptools>=42",
-        "toml",
+        "tomli",
     ]
     if backend == "lightning_gpu":
         requires.append("custatevec-cu12")

setup.py

@@ -16,13 +16,39 @@
 import subprocess
 import shutil
 import sys
-import toml
+
+from importlib import import_module
+from importlib.util import find_spec
 
 from pathlib import Path
 from setuptools import setup, Extension, find_namespace_packages
 from setuptools.command.build_ext import build_ext
 
-project_name = toml.load("pyproject.toml")['project']['name']
+
+has_toml = False
+toml_libs = ["tomli", "tomllib", "tomlkit", "toml"]
+for pkg in toml_libs:
+    spec = find_spec(pkg)
+    if spec:
+        toml = import_module(pkg)
+        has_toml = True
+        break
+
+if not has_toml:
+    raise ImportError(
+        "A TOML parser is required to configure 'pyproject.toml'. "
+        f"We support any of the following TOML parsers: {toml_libs} "
+        "You can install tomlkit via `pip install tomlkit`, or tomli via `pip install tomli`, "
+        "or use Python 3.11 or above which natively offers the tomllib library."
+    )
+
+try:
+    with open("pyproject.toml", "rb") as f:
+        project_name = toml.load(f)['project']['name']
+except TypeError:
+    # To support toml and tomli APIs
+    project_name = toml.load("pyproject.toml")['project']['name']
+
 backend = project_name.replace("PennyLane_", "").lower()
 if (backend == "lightning"): backend = "lightning_qubit"