Add backtracking tests for distribution incompatibilities (#2839)

## Summary

Demonstrates some suboptimal behavior in how we handle invalid metadata,
which are fixed in https://github.com/astral-sh/uv/pull/2834.

The included wheels were modified by-hand to include invalid structures.

crates/uv/tests/pip_compile.rs

@@ -4397,6 +4397,50 @@ fn offline_registry() -> Result<()> {
     Ok(())
 }
 
+/// Resolve a registry package without network access via the `--offline` flag. We should backtrack
+/// to the latest version of the package that's available in the cache.
+#[test]
+fn offline_registry_backtrack() -> Result<()> {
+    let context = TestContext::new("3.12");
+    let requirements_in = context.temp_dir.child("requirements.in");
+    requirements_in.write_str("iniconfig==1.1.1")?;
+
+    // Populate the cache.
+    uv_snapshot!(context.compile()
+            .arg("requirements.in"), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+    # This file was autogenerated by uv via the following command:
+    #    uv pip compile --cache-dir [CACHE_DIR] --exclude-newer 2024-03-25T00:00:00Z requirements.in
+    iniconfig==1.1.1
+
+    ----- stderr -----
+    Resolved 1 package in [TIME]
+    "###
+    );
+
+    // Resolve with `--offline`, with a looser requirement. We should backtrack to `1.1.1`, but
+    // we don't right now.
+    let requirements_in = context.temp_dir.child("requirements.in");
+    requirements_in.write_str("iniconfig")?;
+
+    uv_snapshot!(context.compile()
+            .arg("requirements.in")
+            .arg("--offline"), @r###"
+    success: false
+    exit_code: 2
+    ----- stdout -----
+
+    ----- stderr -----
+    error: Failed to download: iniconfig==2.0.0
+      Caused by: Network connectivity is disabled, but the requested data wasn't found in the cache for: `https://files.pythonhosted.org/packages/ef/a6/62565a6e1cf69e10f5727360368e451d4b7f58beeac6173dc9db836a5b46/iniconfig-2.0.0-py3-none-any.whl.metadata`
+    "###
+    );
+
+    Ok(())
+}
+
 /// Resolve a package without network access via the `--offline` flag, using `--find-links` for an
 /// HTML registry.
 #[test]
@@ -4504,6 +4548,90 @@ fn offline_direct_url() -> Result<()> {
     Ok(())
 }
 
+/// Resolve a package with invalid metadata, by way of an invalid `Requires-Python` field in the
+/// `METADATA` file.
+#[test]
+fn invalid_metadata_requires_python() -> Result<()> {
+    let context = TestContext::new("3.12");
+    let requirements_in = context.temp_dir.child("requirements.in");
+    requirements_in.write_str("validation==2.0.0")?;
+
+    // `2.0.0` has invalid metadata.
+    uv_snapshot!(context.compile()
+            .arg("requirements.in")
+            .arg("--no-index")
+            .arg("--find-links")
+            .arg(context.workspace_root.join("scripts").join("links")), @r###"
+    success: false
+    exit_code: 2
+    ----- stdout -----
+
+    ----- stderr -----
+    error: Failed to download: validation==2.0.0
+      Caused by: Couldn't parse metadata of validation-2.0.0-py3-none-any.whl from validation==2.0.0
+      Caused by: Failed to parse version: Unexpected end of version specifier, expected operator:
+    12
+    ^^
+
+    "###
+    );
+
+    Ok(())
+}
+
+/// Resolve a package with multiple `.dist-info` directories.
+#[test]
+fn invalid_metadata_multiple_dist_info() -> Result<()> {
+    let context = TestContext::new("3.12");
+    let requirements_in = context.temp_dir.child("requirements.in");
+    requirements_in.write_str("validation==3.0.0")?;
+
+    // `3.0.0` has an invalid structure (multiple `.dist-info` directories).
+    uv_snapshot!(context.compile()
+            .arg("requirements.in")
+            .arg("--no-index")
+            .arg("--find-links")
+            .arg(context.workspace_root.join("scripts").join("links")), @r###"
+    success: false
+    exit_code: 2
+    ----- stdout -----
+
+    ----- stderr -----
+    error: Failed to download: validation==3.0.0
+      Caused by: Multiple .dist-info directories found: validation-2.0.0, validation-3.0.0
+    "###
+    );
+
+    Ok(())
+}
+
+/// Resolve a package, but backtrack past versions with invalid metadata.
+#[test]
+fn invalid_metadata_backtrack() -> Result<()> {
+    let context = TestContext::new("3.12");
+    let requirements_in = context.temp_dir.child("requirements.in");
+    requirements_in.write_str("validation")?;
+
+    // `2.0.0` and `3.0.0` have invalid metadata. We should backtrack to `1.0.0` (the preceding
+    // version, which has valid metadata), but we don't right now.
+    uv_snapshot!(context.compile()
+            .arg("requirements.in")
+            .arg("--no-index")
+            .arg("--find-links")
+            .arg(context.workspace_root.join("scripts").join("links")), @r###"
+    success: false
+    exit_code: 2
+    ----- stdout -----
+
+    ----- stderr -----
+    error: Failed to download: validation==3.0.0
+      Caused by: Multiple .dist-info directories found: validation-2.0.0, validation-3.0.0
+    "###
+    );
+
+    Ok(())
+}
+
 /// Resolve nested `-r` requirements files with relative paths.
 #[test]
 fn compile_relative_subfile() -> Result<()> {