Support resolving for an alternate Python distribution (#364)

## Summary Low-priority but fun thing to end the day. You can now pass `--target-version py37`, and we'll generate a resolution for Python 3.7. See: https://github.com/astral-sh/puffin/issues/183.
2023-11-08 15:19:16 -08:00
parent d407bbbee6
commit cfd84d6365
6 changed files with 245 additions and 10 deletions
@@ -0,0 +1,70 @@
+use std::str::FromStr;
+
+use pep508_rs::{MarkerEnvironment, StringVersion};
+
+#[derive(Debug, Clone, Copy, clap::ValueEnum)]
+pub(crate) enum PythonVersion {
+    Py37,
+    Py38,
+    Py39,
+    Py310,
+    Py311,
+    Py312,
+}
+
+impl PythonVersion {
+    /// Return the `python_version` marker for a [`PythonVersion`].
+    fn python_version(self) -> &'static str {
+        match self {
+            Self::Py37 => "3.7",
+            Self::Py38 => "3.8",
+            Self::Py39 => "3.9",
+            Self::Py310 => "3.10",
+            Self::Py311 => "3.11",
+            Self::Py312 => "3.12",
+        }
+    }
+
+    /// Return the `python_full_version` marker for a [`PythonVersion`].
+    fn python_full_version(self) -> &'static str {
+        match self {
+            Self::Py37 => "3.7.0",
+            Self::Py38 => "3.8.0",
+            Self::Py39 => "3.9.0",
+            Self::Py310 => "3.10.0",
+            Self::Py311 => "3.11.0",
+            Self::Py312 => "3.12.0",
+        }
+    }
+
+    /// Return the `implementation_version` marker for a [`PythonVersion`].
+    fn implementation_version(self) -> &'static str {
+        match self {
+            Self::Py37 => "3.7.0",
+            Self::Py38 => "3.8.0",
+            Self::Py39 => "3.9.0",
+            Self::Py310 => "3.10.0",
+            Self::Py311 => "3.11.0",
+            Self::Py312 => "3.12.0",
+        }
+    }
+
+    /// Return a [`MarkerEnvironment`] compatible with the given [`PythonVersion`], based on
+    /// a base [`MarkerEnvironment`].
+    ///
+    /// The returned [`MarkerEnvironment`] will preserve the base environment's platform markers,
+    /// but override its Python version markers.
+    pub(crate) fn markers(self, base: &MarkerEnvironment) -> MarkerEnvironment {
+        let mut markers = base.clone();
+        // Ex) `python_version == "3.12"`
+        markers.python_version = StringVersion::from_str(self.python_version()).unwrap();
+        // Ex) `python_full_version == "3.12.0"`
+        markers.python_full_version = StringVersion::from_str(self.python_full_version()).unwrap();
+        // Ex) `implementation_version == "3.12.0"`
+        if markers.implementation_name == "cpython" {
+            markers.implementation_version =
+                StringVersion::from_str(self.implementation_version()).unwrap();
+        }
+        markers
+    }
+}