Add test coverage for --python-version overriding UV_PYTHON entirely

crates/uv/tests/it/pip_compile.rs

@@ -1737,13 +1737,14 @@ fn compile_python_build_version_different_than_target() -> Result<()> {
         .arg("requirements.in")
         .arg("--python-version")
         .arg("3.12")
-        .env(EnvVars::UV_PYTHON, "3.11")
+        .arg("-p")
+        .arg("[email protected]")
         .env_remove(EnvVars::VIRTUAL_ENV), @r###"
     success: true
     exit_code: 0
     ----- stdout -----
     # This file was autogenerated by uv via the following command:
-    #    uv pip compile --cache-dir [CACHE_DIR] requirements.in --python-version 3.12
+    #    uv pip compile --cache-dir [CACHE_DIR] requirements.in --python-version 3.12 -p [email protected]
     black==23.10.[X]
         # via -r requirements.in
     click==8.1.7
@@ -1762,18 +1763,51 @@ fn compile_python_build_version_different_than_target() -> Result<()> {
     "###
     );
 
+    // If we can't find the interpreter, we fail
     uv_snapshot!(context.filters(), context.pip_compile()
         .arg("requirements.in")
         .arg("--python-version")
         .arg("3.12")
         .arg("-p")
-        .arg("[email protected]")
+        .arg("[email protected]")
+        .env_remove(EnvVars::VIRTUAL_ENV), @r###"
+    success: false
+    exit_code: 2
+    ----- stdout -----
+
+    ----- stderr -----
+    error: No interpreter found for PyPy 3.11 in [PYTHON SOURCES]
+    "###
+    );
+
+    uv_snapshot!(context.filters(), context.pip_compile()
+        .arg("requirements.in")
+        .arg("--python-version")
+        .arg("3.12")
+        .arg("-p")
+        .arg("3.13")
+        .env_remove(EnvVars::VIRTUAL_ENV), @r###"
+    success: false
+    exit_code: 2
+    ----- stdout -----
+
+    ----- stderr -----
+    error: No interpreter found for Python 3.13 in [PYTHON SOURCES]
+    "###
+    );
+
+    // `UV_PYTHON` is ignored if `--python-version` is set
+    uv_snapshot!(context.filters(), context.pip_compile()
+        .arg("requirements.in")
+        .arg("--python-version")
+        .arg("3.12")
+        .env(EnvVars::UV_PYTHON, "3.11")
         .env_remove(EnvVars::VIRTUAL_ENV), @r###"
     success: true
     exit_code: 0
     ----- stdout -----
     # This file was autogenerated by uv via the following command:
-    #    uv pip compile --cache-dir [CACHE_DIR] requirements.in --python-version 3.12 -p [email protected]
+    #    uv pip compile --cache-dir [CACHE_DIR] requirements.in --python-version 3.12
     black==23.10.[X]
         # via -r requirements.in
     click==8.1.7
@@ -1792,36 +1826,33 @@ fn compile_python_build_version_different_than_target() -> Result<()> {
     "###
     );
 
-    // If we can't find the interpreter, we fail
-    uv_snapshot!(context.filters(), context.pip_compile()
-        .arg("requirements.in")
-        .arg("--python-version")
-        .arg("3.12")
-        .arg("-p")
-        .arg("[email protected]")
-        .env_remove(EnvVars::VIRTUAL_ENV), @r###"
-    success: false
-    exit_code: 2
-    ----- stdout -----
-
-    ----- stderr -----
-    error: No interpreter found for PyPy 3.11 in [PYTHON SOURCES]
-    "###
-    );
-
+    // `UV_PYTHON` is ignored if `--python-version` is set
     uv_snapshot!(context.filters(), context.pip_compile()
         .arg("requirements.in")
         .arg("--python-version")
         .arg("3.12")
-        .arg("-p")
-        .arg("3.13")
+        .env(EnvVars::UV_PYTHON, "pypy")
         .env_remove(EnvVars::VIRTUAL_ENV), @r###"
-    success: false
-    exit_code: 2
+    success: true
+    exit_code: 0
     ----- stdout -----
+    # This file was autogenerated by uv via the following command:
+    #    uv pip compile --cache-dir [CACHE_DIR] requirements.in --python-version 3.12
+    black==23.10.[X]
+        # via -r requirements.in
+    click==8.1.7
+        # via black
+    mypy-extensions==1.0.0
+        # via black
+    packaging==24.0
+        # via black
+    pathspec==0.12.1
+        # via black
+    platformdirs==4.2.0
+        # via black
 
     ----- stderr -----
-    error: No interpreter found for Python 3.13 in [PYTHON SOURCES]
+    Resolved 6 packages in [TIME]
     "###
     );