Start implementation of support for pyproject.yml

Related to #1427

Author: rgaiacs

repo2docker/buildpacks/pyproject/__init__.py

@@ -0,0 +1,125 @@
+"""Buildpack for Git repositories with pyproject.toml
+
+Support to pyproject.toml was added to pip v10.0,
+see https://pip.pypa.io/en/latest/reference/build-system/pyproject-toml/.
+"""
+
+import os
+import re
+import tomllib
+from functools import lru_cache
+
+from ..conda import CondaBuildPack
+
+VERSION_PAT = re.compile(r"\d+(\.\d+)*")
+
+
+class PyprojectBuildPack(CondaBuildPack):
+    """Setup Python with pyproject.toml for use with a repository."""
+
+    @property
+    def python_version(self):
+        """
+        Detect the Python version declared in a `pyproject.toml`.
+        Will return 'x.y' if version is found (e.g '3.6'),
+        or a Falsy empty string '' if not found.
+        """
+
+        if hasattr(self, "_python_version"):
+            return self._python_version
+
+        pyproject_file = self.binder_path("pyproject.toml")
+        with open(pyproject_file, "rb") as _pyproject_file:
+            pyproject_toml = tomllib.load(_pyproject_file)
+
+        if "project" in pyproject_toml:
+            if "requires-python" in pyproject_toml["project"]:
+                raw_version = pyproject_toml["project"]["requires-python"]
+
+                match = VERSION_PAT.match(raw_version)
+                if match:
+                    return match.group()
+
+        return ""
+
+    @lru_cache
+    def get_preassemble_script_files(self):
+        """Return files needed for preassembly"""
+        files = super().get_preassemble_script_files()
+        path = self.binder_path("pyproject.toml")
+        if os.path.exists(path):
+            files[path] = path
+        return files
+
+    @lru_cache
+    def get_preassemble_scripts(self):
+        """scripts to run prior to staging the repo contents"""
+        scripts = super().get_preassemble_scripts()
+        # install pipenv to install dependencies within Pipfile.lock or Pipfile
+        if V(self.python_version) < V("3.6"):
+            # last pipenv version to support 2.7, 3.5
+            pipenv_version = "2021.5.29"
+        else:
+            pipenv_version = "2022.1.8"
+        scripts.append(
+            (
+                "${NB_USER}",
+                f"${{KERNEL_PYTHON_PREFIX}}/bin/pip install --no-cache-dir pipenv=={pipenv_version}",
+            )
+        )
+        return scripts
+
+    @lru_cache
+    def get_assemble_scripts(self):
+        """Return series of build-steps specific to this repository."""
+        # If we have pyproject.toml declare the
+        # use of Python 2, Python 2.7 will be made available in the *kernel*
+        # environment. The notebook servers environment on the other hand
+        # requires Python 3 but may require something additional installed in it
+        # still such as `nbgitpuller`. For this purpose, a "requirements3.txt"
+        # file will be used to install dependencies for the notebook servers
+        # environment, if Python 2 had been specified for the kernel
+        # environment.
+        assemble_scripts = super().get_assemble_scripts()
+
+        if self.separate_kernel_env:
+            # using legacy Python (e.g. 2.7) as a kernel
+
+            # requirements3.txt allows for packages to be installed to the
+            # notebook servers Python environment
+            nb_requirements_file = self.binder_path("requirements3.txt")
+            if os.path.exists(nb_requirements_file):
+                assemble_scripts.append(
+                    (
+                        "${NB_USER}",
+                        f'${{NB_PYTHON_PREFIX}}/bin/pip install --no-cache-dir -r "{nb_requirements_file}"',
+                    )
+                )
+
+        assemble_scripts.append(
+            (
+                "${NB_USER}",
+                """(cd  && \\
+                    PATH="${{KERNEL_PYTHON_PREFIX}}/bin:$PATH" \\
+                        pip install --no-cache-dir --editable {working_directory}
+                )""".format(
+                    working_directory=working_directory,
+                ),
+            )
+        )
+
+        return assemble_scripts
+
+    def detect(self):
+        """Check if current repo should be built with the pyproject.toml buildpack."""
+        # first make sure python is not explicitly unwanted
+        runtime_txt = self.binder_path("runtime.txt")
+        if os.path.exists(runtime_txt):
+            with open(runtime_txt) as f:
+                runtime = f.read().strip()
+            if not runtime.startswith("python-"):
+                return False
+
+        pyproject_file = self.binder_path("pyproject.toml")
+
+        return os.path.exists(pyproject_file)