Support granular target Python versions (#534)

## Summary

Allows, e.g., `--python-version 3.7` or `--python-version 3.7.9`. This
was also feedback I received in the original PR.

Closes https://github.com/astral-sh/puffin/issues/533.

crates/puffin-cli/src/main.rs

@@ -59,6 +59,7 @@ struct Cli {
 }
 
 #[derive(Subcommand)]
+#[allow(clippy::large_enum_variant)]
 enum Commands {
     /// Compile a `requirements.in` file to a `requirements.txt` file.
     PipCompile(PipCompileArgs),
@@ -148,7 +149,11 @@ struct PipCompileArgs {
     #[clap(long)]
     no_build: bool,
 
-    /// The minimum Python version that should be supported.
+    /// The minimum Python version that should be supported by the compiled requirements (e.g.,
+    /// `3.7` or `3.7.9`).
+    ///
+    /// If a patch version is omitted, the most recent known patch version for that minor version
+    /// is assumed. For example, `3.7` is mapped to `3.7.17`.
     #[arg(long, short, value_enum)]
     python_version: Option<PythonVersion>,
 

crates/puffin-cli/src/python_version.rs

@@ -1,54 +1,65 @@
 use std::str::FromStr;
+use tracing::debug;
 
+use pep440_rs::Version;
 use pep508_rs::{MarkerEnvironment, StringVersion};
 
-#[derive(Debug, Clone, Copy, clap::ValueEnum)]
+#[derive(Debug, Clone)]
-pub(crate) enum PythonVersion {
+pub(crate) struct PythonVersion(StringVersion);
-    Py37,
+
-    Py38,
+impl FromStr for PythonVersion {
-    Py39,
+    type Err = String;
-    Py310,
+
-    Py311,
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
-    Py312,
+        let version = StringVersion::from_str(s)?;
+        if version.is_dev() {
+            return Err(format!("Python version {s} is a development release"));
+        }
+        if version.is_local() {
+            return Err(format!("Python version {s} is a local version"));
+        }
+        if version.epoch != 0 {
+            return Err(format!("Python version {s} has a non-zero epoch"));
+        }
+        if version.version < Version::from_release(vec![3, 7]) {
+            return Err(format!("Python version {s} must be >= 3.7"));
+        }
+        if version.version >= Version::from_release(vec![4, 0]) {
+            return Err(format!("Python version {s} must be < 4.0"));
+        }
+
+        // If the version lacks a patch, assume the most recent known patch for that minor version.
+        match version.release.as_slice() {
+            [3, 7] => {
+                debug!("Assuming Python 3.7.17");
+                Ok(Self(StringVersion::from_str("3.7.17")?))
+            }
+            [3, 8] => {
+                debug!("Assuming Python 3.8.18");
+                Ok(Self(StringVersion::from_str("3.8.18")?))
+            }
+            [3, 9] => {
+                debug!("Assuming Python 3.9.18");
+                Ok(Self(StringVersion::from_str("3.9.18")?))
+            }
+            [3, 10] => {
+                debug!("Assuming Python 3.10.13");
+                Ok(Self(StringVersion::from_str("3.10.13")?))
+            }
+            [3, 11] => {
+                debug!("Assuming Python 3.11.6");
+                Ok(Self(StringVersion::from_str("3.11.6")?))
+            }
+            [3, 12] => {
+                debug!("Assuming Python 3.12.0");
+                Ok(Self(StringVersion::from_str("3.12.0")?))
+            }
+            _ => Ok(Self(version)),
+        }
+    }
 }
 
 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`].
     ///
@@ -56,15 +67,18 @@ impl PythonVersion {
     /// 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 =
+            markers.implementation_version = self.0.clone();
-                StringVersion::from_str(self.implementation_version()).unwrap();
         }
+
+        // Ex) `python_full_version == "3.12.0"`
+        markers.python_full_version = self.0.clone();
+
+        // Ex) `python_version == "3.12"`
+        markers.python_version = self.0;
+
         markers
     }
 }

crates/puffin-cli/tests/pip_compile.rs

@@ -473,7 +473,7 @@ fn compile_python_312() -> Result<()> {
             .arg("pip-compile")
             .arg("requirements.in")
             .arg("--python-version")
-            .arg("py312")
+            .arg("3.12")
             .arg("--cache-dir")
             .arg(cache_dir.path())
             .arg("--exclude-newer")
@@ -502,7 +502,7 @@ fn compile_python_37() -> Result<()> {
             .arg("pip-compile")
             .arg("requirements.in")
             .arg("--python-version")
-            .arg("py37")
+            .arg("3.7")
             .arg("--cache-dir")
             .arg(cache_dir.path())
             .arg("--exclude-newer")
@@ -514,6 +514,50 @@ fn compile_python_37() -> Result<()> {
     Ok(())
 }
 
+/// Resolve a specific version of Black against an invalid Python version.
+#[test]
+fn compile_python_invalid_version() -> Result<()> {
+    let temp_dir = TempDir::new()?;
+
+    let requirements_in = temp_dir.child("requirements.in");
+    requirements_in.write_str("black==23.10.1")?;
+
+    insta::with_settings!({
+        filters => INSTA_FILTERS.to_vec()
+    }, {
+        assert_cmd_snapshot!(Command::new(get_cargo_bin(BIN_NAME))
+            .arg("pip-compile")
+            .arg("requirements.in")
+            .arg("--python-version")
+            .arg("3.7.x")
+            .current_dir(&temp_dir));
+    });
+
+    Ok(())
+}
+
+/// Resolve a specific version of Black against an invalid Python version.
+#[test]
+fn compile_python_dev_version() -> Result<()> {
+    let temp_dir = TempDir::new()?;
+
+    let requirements_in = temp_dir.child("requirements.in");
+    requirements_in.write_str("black==23.10.1")?;
+
+    insta::with_settings!({
+        filters => INSTA_FILTERS.to_vec()
+    }, {
+        assert_cmd_snapshot!(Command::new(get_cargo_bin(BIN_NAME))
+            .arg("pip-compile")
+            .arg("requirements.in")
+            .arg("--python-version")
+            .arg("3.7-dev")
+            .current_dir(&temp_dir));
+    });
+
+    Ok(())
+}
+
 /// Test that we select the last 3.8 compatible numpy version instead of trying to compile an
 /// incompatible sdist <https://github.com/astral-sh/puffin/issues/388>
 #[test]

crates/puffin-cli/tests/snapshots/pip_compile__compile_python_312.snap

@@ -6,17 +6,19 @@ info:
     - pip-compile
     - requirements.in
     - "--python-version"
-    - py312
+    - "3.12"
     - "--cache-dir"
-    - /tmp/.tmp4asOTQ
+    - /var/folders/nt/6gf2v7_s3k13zq_t3944rwz40000gn/T/.tmpBGkaCR
+    - "--exclude-newer"
+    - "2023-11-18T12:00:00Z"
   env:
-    VIRTUAL_ENV: /tmp/.tmpjRCdtR/.venv
+    VIRTUAL_ENV: /var/folders/nt/6gf2v7_s3k13zq_t3944rwz40000gn/T/.tmpfxl60Y/.venv
 ---
 success: true
 exit_code: 0
 ----- stdout -----
 # This file was autogenerated by Puffin v0.0.1 via the following command:
-#    puffin pip-compile requirements.in --python-version py312 --cache-dir [CACHE_DIR]
+#    puffin pip-compile requirements.in --python-version 3.12 --cache-dir [CACHE_DIR]
 black==23.10.1
 click==8.1.7
     # via black

crates/puffin-cli/tests/snapshots/pip_compile__compile_python_dev_version.snap

@@ -0,0 +1,19 @@
+---
+source: crates/puffin-cli/tests/pip_compile.rs
+info:
+  program: puffin
+  args:
+    - pip-compile
+    - requirements.in
+    - "--python-version"
+    - 3.7-dev
+---
+success: false
+exit_code: 2
+----- stdout -----
+
+----- stderr -----
+error: invalid value '3.7-dev' for '--python-version <PYTHON_VERSION>': Python version 3.7-dev is a development release
+
+For more information, try '--help'.
+

crates/puffin-cli/tests/snapshots/pip_compile__compile_python_invalid_version.snap

@@ -0,0 +1,19 @@
+---
+source: crates/puffin-cli/tests/pip_compile.rs
+info:
+  program: puffin
+  args:
+    - pip-compile
+    - requirements.in
+    - "--python-version"
+    - 3.7.x
+---
+success: false
+exit_code: 2
+----- stdout -----
+
+----- stderr -----
+error: invalid value '3.7.x' for '--python-version <PYTHON_VERSION>': Version `3.7.x` doesn't match PEP 440 rules
+
+For more information, try '--help'.
+