refactor: modernize build & test system

.codecov.yml

@@ -12,7 +12,3 @@ comment:
   require_base: false # [true :: must have a base report to post]
   require_head: false # [true :: must have a head report to post]
   hide_project_coverage: false # [true :: only show coverage on the git diff aka patch coverage]
-
-# SCons compiles copies of the sources in build/coverage-<arch>/, map them back to src/
-fixes:
-  - "build/coverage-x86_64/::src/"

.github/ISSUE_TEMPLATE/release_checklist.md

@@ -14,8 +14,8 @@ assignees: ""
 - [ ] Locally rendered documentation contains all appropriate pages and other human-written text is up-to-date with any changes in the code.
 - [ ] Installation instructions in the README, documentation, and the website are updated.
 - [ ] Grammar and writing quality are checked (no typos).
-- [ ] Review `FALLBACK_VERSION` in `site_scons/fallback_version.py` for builds without a resolvable release tag.
-- [ ] `scons test` passes locally with the latest conda-forge compilers and dependencies.
+- [ ] Review `LIBDIFFPY_FALLBACK_VERSION` in `cmake/FallbackVersion.cmake` for builds without a resolvable release tag.
+- [ ] The unit tests pass locally (`cmake --preset debug`, `cmake --build --preset debug`, `ctest --preset debug`) with the latest conda-forge compilers and dependencies.
 - [ ] Dispatch matrix testing to test the release on all systems. If you do not have permission to run this workflow, tag the maintainer and say `@maintainer, please dispatch matrix testing workflow`. Matrix testing also runs automatically after a GitHub release is published, but it does not block the release, so check that it passes.
 
 Please tag the maintainer (e.g., @username) in the comment here when you are ready for the GitHub release. Include any additional comments necessary, such as version information and details about the pre-release here:

.github/actions/setup-tests/action.yml

@@ -7,13 +7,6 @@ runs:
       shell: bash
       run: git fetch --tags https://github.com/diffpy/libdiffpy.git
 
-    - name: Check out CxxTest 4.4
-      uses: actions/checkout@v6
-      with:
-        repository: CxxTest/cxxtest
-        ref: 191adddb3876ab389c0c856e1c03874bf70f8ee4
-        path: build/cxxtest
-
     - name: Prepare C++ test configuration
       shell: python {0}
       run: |

.github/scripts/configure-tests.py

@@ -1,4 +1,4 @@
-"""Configure SCons, CxxTest and the conda environment for CI tests."""
+"""Write the conda environment file for the CI tests."""
 
 import json
 from pathlib import Path
@@ -7,7 +7,7 @@
 for filename in ("build.txt", "conda.txt", "tests.txt"):
     for line in (Path("requirements") / filename).read_text().splitlines():
         spec = line.split("#", 1)[0].strip()
-        if spec and spec != "cxxtest":
+        if spec:
             requirements.append(spec)
 
 Path("build").mkdir(exist_ok=True)
@@ -22,34 +22,3 @@
     )
     + "\n"
 )
-
-Path("sconscript.local").write_text("""\
-Import('env')
-import os
-import sys
-
-prefix = os.environ['CONDA_PREFIX']
-cxxtest = Dir('#/build/cxxtest').abspath
-env.Replace(CXXTEST=os.path.join(cxxtest, 'bin', 'cxxtestgen'),
-            CXXTEST_INSTALL_DIR=cxxtest, CXXTEST_PYTHON=sys.executable)
-
-if env['PLATFORM'] == 'win32':
-    from SCons.Platform.win32 import exec_spawn
-
-    # The outer CI shell already activates conda and SCons configures MSVC.
-    # /D stops each compiler/test-generator child from repeating cmd AutoRun.
-    def spawn_without_autorun(sh, escape, cmd, args, child_env):
-        return exec_spawn([sh, '/D', '/C', escape(' '.join(args))], child_env)
-
-    env['SPAWN'] = spawn_without_autorun
-else:
-    env.Replace(CXX=os.environ.get('CXX', os.path.join(prefix, 'bin', 'c++')))
-    env.Prepend(CCFLAGS=['-isystem' + os.path.join(prefix, 'include')])
-    env.Append(LIBPATH=os.path.join(prefix, 'lib'))
-    env.Append(LINKFLAGS='-Wl,-rpath,' + os.path.join(prefix, 'lib'))
-    if env['PLATFORM'] == 'darwin':
-        sdk = os.environ.get('CONDA_BUILD_SYSROOT')
-        if sdk:
-            env.Append(CXXFLAGS=['-isysroot', sdk])
-            env.Append(LINKFLAGS=['-isysroot', sdk])
-""")

.github/workflows/matrix-and-codecov.yml

@@ -27,19 +27,21 @@ jobs:
         include:
           - os: ubuntu-latest
             shell: bash -l {0}
-            build: coverage
+            build-type: Debug
+            coverage: "ON"
             jobs: 4
           - os: windows-latest
             shell: cmd /C CALL {0}
-            build: fast
             jobs: 4
           - os: macos-latest
             shell: bash -l {0}
-            build: fast
+            build-type: Release
+            coverage: "OFF"
             jobs: 2
           - os: macos-15-intel
             shell: bash -l {0}
-            build: fast
+            build-type: Release
+            coverage: "OFF"
             jobs: 4
     defaults:
       run:
@@ -55,13 +57,29 @@ jobs:
         uses: ./.github/actions/setup-tests
 
       - name: Build and run C++ tests
-        run: scons -j${{ matrix.jobs }} build=${{ matrix.build }} test
+        if: runner.os != 'Windows'
+        run: |
+          cmake -S . -B build/ci -G Ninja $CMAKE_ARGS \
+            -DCMAKE_BUILD_TYPE=${{ matrix.build-type }} \
+            -DLIBDIFFPY_COVERAGE=${{ matrix.coverage }} \
+            -DLIBDIFFPY_BUILD_TESTS=ON
+          cmake --build build/ci --parallel ${{ matrix.jobs }}
+          ctest --test-dir build/ci --output-on-failure
+
+      # The conda cxx-compiler activation configures MSVC for Ninja in cmd.
+      - name: Build and run C++ tests (Windows)
+        if: runner.os == 'Windows'
+        run: |
+          where cl.exe || exit /b 1
+          cmake --preset release -DLIBDIFFPY_BUILD_TESTS=ON || exit /b 1
+          cmake --build --preset release --parallel ${{ matrix.jobs }} || exit /b 1
+          ctest --test-dir build\release --output-on-failure --no-tests=error
 
       - name: Generate coverage report
         if: runner.os == 'Linux'
         run: >-
           gcovr --gcov-executable "$CONDA_PREFIX/bin/gcov"
-          --root . --filter 'build/coverage-.*/diffpy/'
+          --root . --filter 'src/diffpy/'
           --xml coverage.xml
 
       - name: Save coverage report

.github/workflows/tests-on-pr.yml

@@ -27,12 +27,15 @@ jobs:
       - name: Build and run C++ tests with coverage
         run: |
           "$CONDA_PREFIX/bin/c++" --version
-          scons -j4 build=coverage test
+          cmake --preset coverage $CMAKE_ARGS \
+            -DCMAKE_INSTALL_LIBDIR=lib/x86_64-linux-gnu
+          cmake --build --preset coverage --parallel 4
+          ctest --preset coverage
 
       - name: Generate coverage report
         run: >-
           gcovr --gcov-executable "$CONDA_PREFIX/bin/gcov"
-          --root . --filter 'build/coverage-.*/diffpy/'
+          --root . --filter 'src/diffpy/'
           --xml coverage.xml
 
       - name: Upload coverage to Codecov

.gitignore

@@ -19,11 +19,8 @@ __pycache__/
 *.la
 *.a
 
-# SCons build files
-.sconf_temp/
-.sconsign.dblite
-/sconscript.local
-/sconsvars.py
+# CMake user settings
+/CMakeUserPresets.json
 .gdb_history
 tags
 

.pre-commit-config.yaml

@@ -9,10 +9,9 @@ ci:
   autoupdate_schedule: monthly
   skip: [no-commit-to-branch]
   submodules: false
-# Leave the vendored CxxTest SCons tool and the data tables untouched.
+# Leave the data tables untouched.
 exclude: |
   (?x)^(
-    site_scons/site_tools/cxxtest\.py|
     .*\.(cif|dat)
   )$
 repos:

.readthedocs.yaml

@@ -4,6 +4,9 @@ build:
   os: "ubuntu-22.04"
   tools:
     python: "latest"
+  # cmake resolves the documentation version from git tags.
+  apt_packages:
+    - cmake
 
 python:
   install: