Allow round-trip via freeze command (#1936)

## Summary

We're printing the `Display` representation of `InstalledDist`, which
isn't guaranteed to be (and in fact isn't) a valid PEP 508 requirement,
making it impossible to use the `freeze` output as an input to an
install.

Closes https://github.com/astral-sh/uv/issues/1931.

crates/uv/src/commands/pip_freeze.rs

@@ -6,7 +6,7 @@ use itertools::Itertools;
 use owo_colors::OwoColorize;
 use tracing::debug;
 
-use distribution_types::Name;
+use distribution_types::{InstalledDist, Name};
 use platform_host::Platform;
 use uv_cache::Cache;
 use uv_fs::Normalized;
@@ -34,7 +34,18 @@ pub(crate) fn pip_freeze(cache: &Cache, strict: bool, mut printer: Printer) -> R
         .iter()
         .sorted_unstable_by(|a, b| a.name().cmp(b.name()).then(a.version().cmp(b.version())))
     {
-        println!("{dist}");
+        match dist {
+            InstalledDist::Registry(dist) => {
+                println!("{}=={}", dist.name().bold(), dist.version);
+            }
+            InstalledDist::Url(dist) => {
+                if dist.editable {
+                    println!("-e {}", dist.url);
+                } else {
+                    println!("{} @ {}", dist.name().bold(), dist.url);
+                }
+            }
+        }
     }
 
     // Validate that the environment is consistent.

crates/uv/tests/pip_freeze.rs

@@ -3,6 +3,7 @@
 use std::process::Command;
 
 use anyhow::Result;
+use assert_cmd::prelude::*;
 use assert_fs::prelude::*;
 
 use crate::common::{get_bin, uv_snapshot, TestContext};
@@ -22,19 +23,6 @@ fn command(context: &TestContext) -> Command {
     command
 }
 
-/// Create a `pip sync` command with options shared across scenarios.
-fn sync_command(context: &TestContext) -> Command {
-    let mut command = Command::new(get_bin());
-    command
-        .arg("pip")
-        .arg("sync")
-        .arg("--cache-dir")
-        .arg(context.cache_dir.path())
-        .env("VIRTUAL_ENV", context.venv.as_os_str())
-        .current_dir(&context.temp_dir);
-    command
-}
-
 /// List multiple installed packages in a virtual environment.
 #[test]
 fn freeze_many() -> Result<()> {
@@ -44,20 +32,15 @@ fn freeze_many() -> Result<()> {
     requirements_txt.write_str("MarkupSafe==2.1.3\ntomli==2.0.1")?;
 
     // Run `pip sync`.
-    uv_snapshot!(sync_command(&context)
+    Command::new(get_bin())
-        .arg("requirements.txt"), @r###"
+        .arg("pip")
-    success: true
+        .arg("sync")
-    exit_code: 0
+        .arg(requirements_txt.path())
-    ----- stdout -----
+        .arg("--cache-dir")
-
+        .arg(context.cache_dir.path())
-    ----- stderr -----
+        .env("VIRTUAL_ENV", context.venv.as_os_str())
-    Resolved 2 packages in [TIME]
+        .assert()
-    Downloaded 2 packages in [TIME]
+        .success();
-    Installed 2 packages in [TIME]
-     + markupsafe==2.1.3
-     + tomli==2.0.1
-    "###
-    );
 
     // Run `pip freeze`.
     uv_snapshot!(command(&context)
@@ -79,8 +62,6 @@ fn freeze_many() -> Result<()> {
 #[test]
 #[cfg(unix)]
 fn freeze_duplicate() -> Result<()> {
-    use assert_cmd::assert::OutputAssertExt;
-
     use crate::common::{copy_dir_all, INSTA_FILTERS};
 
     // Sync a version of `pip` into a virtual environment.
@@ -157,3 +138,40 @@ fn freeze_duplicate() -> Result<()> {
 
     Ok(())
 }
+
+/// List a direct URL package in a virtual environment.
+#[test]
+fn freeze_url() -> Result<()> {
+    let context = TestContext::new("3.12");
+
+    let requirements_txt = context.temp_dir.child("requirements.txt");
+    requirements_txt.write_str("anyio\niniconfig @ https://files.pythonhosted.org/packages/ef/a6/62565a6e1cf69e10f5727360368e451d4b7f58beeac6173dc9db836a5b46/iniconfig-2.0.0-py3-none-any.whl")?;
+
+    // Run `pip sync`.
+    Command::new(get_bin())
+        .arg("pip")
+        .arg("sync")
+        .arg(requirements_txt.path())
+        .arg("--cache-dir")
+        .arg(context.cache_dir.path())
+        .env("VIRTUAL_ENV", context.venv.as_os_str())
+        .assert()
+        .success();
+
+    // Run `pip freeze`.
+    uv_snapshot!(command(&context)
+        .arg("--strict"), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+    anyio==4.3.0
+    iniconfig @ https://files.pythonhosted.org/packages/ef/a6/62565a6e1cf69e10f5727360368e451d4b7f58beeac6173dc9db836a5b46/iniconfig-2.0.0-py3-none-any.whl
+
+    ----- stderr -----
+    warning: The package `anyio` requires `idna >=2.8`, but it's not installed.
+    warning: The package `anyio` requires `sniffio >=1.1`, but it's not installed.
+    "###
+    );
+
+    Ok(())
+}