Bias towards local directories for bare editable requirements (#3995)

## Summary

Given `install -e dagster`, we need to assume that the user meant
`install -e ./dagster`, even though `install dagster` should _not_ be
treated as `install ./dagster`. I suspect pip will change this in the
future (since `pip install dagster` does _not_ meant `pip install
./dagster`) but for now it's what users expect.

Closes https://github.com/astral-sh/uv/issues/3994.

crates/requirements-txt/src/lib.rs

@@ -44,7 +44,6 @@ use tracing::instrument;
 use unscanny::{Pattern, Scanner};
 use url::Url;
 
-use crate::requirement::EditableError;
 use distribution_types::{UnresolvedRequirement, UnresolvedRequirementSpecification};
 use pep508_rs::{
     expand_env_vars, split_scheme, strip_host, Pep508Error, RequirementOrigin, Scheme, VerbatimUrl,
@@ -57,11 +56,12 @@ use uv_configuration::{NoBinary, NoBuild, PackageNameSpecifier};
 use uv_fs::{normalize_url_path, Simplified};
 use uv_warnings::warn_user;
 
+use crate::requirement::EditableError;
 pub use crate::requirement::RequirementsTxtRequirement;
 
 mod requirement;
 
-/// We emit one of those for each requirements.txt entry
+/// We emit one of those for each `requirements.txt` entry.
 enum RequirementsTxtStatement {
     /// `-r` inclusion filename
     Requirements {
@@ -500,7 +500,8 @@ fn parse_entry(
             Some(requirements_txt)
         };
 
-        let (requirement, hashes) = parse_requirement_and_hashes(s, content, source, working_dir)?;
+        let (requirement, hashes) =
+            parse_requirement_and_hashes(s, content, source, working_dir, true)?;
         let requirement =
             requirement
                 .into_editable()
@@ -579,7 +580,8 @@ fn parse_entry(
             Some(requirements_txt)
         };
 
-        let (requirement, hashes) = parse_requirement_and_hashes(s, content, source, working_dir)?;
+        let (requirement, hashes) =
+            parse_requirement_and_hashes(s, content, source, working_dir, false)?;
         RequirementsTxtStatement::RequirementEntry(RequirementEntry {
             requirement,
             hashes,
@@ -643,6 +645,7 @@ fn parse_requirement_and_hashes(
     content: &str,
     source: Option<&Path>,
     working_dir: &Path,
+    editable: bool,
 ) -> Result<(RequirementsTxtRequirement, Vec<String>), RequirementsTxtParserError> {
     // PEP 508 requirement
     let start = s.cursor();
@@ -699,7 +702,7 @@ fn parse_requirement_and_hashes(
         }
     }
 
-    let requirement = RequirementsTxtRequirement::parse(requirement, working_dir)
+    let requirement = RequirementsTxtRequirement::parse(requirement, working_dir, editable)
         .map(|requirement| {
             if let Some(source) = source {
                 requirement.with_origin(RequirementOrigin::File(source.to_path_buf()))

crates/requirements-txt/src/requirement.rs

@@ -119,10 +119,22 @@ impl RequirementsTxtRequirement {
     pub fn parse(
         input: &str,
         working_dir: impl AsRef<Path>,
+        editable: bool,
     ) -> Result<Self, Box<Pep508Error<VerbatimParsedUrl>>> {
         // Attempt to parse as a PEP 508-compliant requirement.
         match pep508_rs::Requirement::parse(input, &working_dir) {
-            Ok(requirement) => Ok(Self::Named(requirement)),
+            Ok(requirement) => {
+                // As a special-case, interpret `dagster` as `./dagster` if we're in editable mode.
+                if editable && requirement.version_or_url.is_none() {
+                    Ok(Self::Unnamed(UnnamedRequirement::parse(
+                        input,
+                        &working_dir,
+                        &mut TracingReporter,
+                    )?))
+                } else {
+                    Ok(Self::Named(requirement))
+                }
+            }
             Err(err) => match err.message {
                 Pep508ErrorSource::UnsupportedRequirement(_) => {
                     // If that fails, attempt to parse as a direct URL requirement.

crates/uv-requirements/src/specification.rs

@@ -86,16 +86,18 @@ impl RequirementsSpecification {
     ) -> Result<Self> {
         Ok(match source {
             RequirementsSource::Package(name) => {
-                let requirement = RequirementsTxtRequirement::parse(name, std::env::current_dir()?)
-                    .with_context(|| format!("Failed to parse: `{name}`"))?;
+                let requirement =
+                    RequirementsTxtRequirement::parse(name, std::env::current_dir()?, false)
+                        .with_context(|| format!("Failed to parse: `{name}`"))?;
                 Self {
                     requirements: vec![UnresolvedRequirementSpecification::from(requirement)],
                     ..Self::default()
                 }
             }
             RequirementsSource::Editable(name) => {
-                let requirement = RequirementsTxtRequirement::parse(name, std::env::current_dir()?)
-                    .with_context(|| format!("Failed to parse: `{name}`"))?;
+                let requirement =
+                    RequirementsTxtRequirement::parse(name, std::env::current_dir()?, true)
+                        .with_context(|| format!("Failed to parse: `{name}`"))?;
                 Self {
                     requirements: vec![UnresolvedRequirementSpecification::from(
                         requirement.into_editable()?,

crates/uv/tests/pip_install.rs

@@ -1114,22 +1114,50 @@ fn install_editable_pep_508_cli() {
 }
 
 #[test]
-fn invalid_editable_no_version() -> Result<()> {
+fn install_editable_bare_cli() {
     let context = TestContext::new("3.12");
 
-    let requirements_txt = context.temp_dir.child("requirements.txt");
-    requirements_txt.write_str("-e black")?;
+    let packages_dir = context.workspace_root.join("scripts/packages");
 
     uv_snapshot!(context.filters(), context.install()
-        .arg("-r")
-        .arg("requirements.txt"), @r###"
-    success: false
-    exit_code: 2
+        .arg("-e")
+        .arg("black_editable")
+        .current_dir(&packages_dir), @r###"
+    success: true
+    exit_code: 0
     ----- stdout -----
 
     ----- stderr -----
-    error: Unsupported editable requirement in `requirements.txt`
-      Caused by: Editable `black` must refer to a local directory
+    Resolved 1 package in [TIME]
+    Downloaded 1 package in [TIME]
+    Installed 1 package in [TIME]
+     + black==0.1.0 (from file://[WORKSPACE]/scripts/packages/black_editable)
+    "###
+    );
+}
+
+#[test]
+fn install_editable_bare_requirements_txt() -> Result<()> {
+    let context = TestContext::new("3.12");
+
+    let requirements_txt = context.temp_dir.child("requirements.txt");
+    requirements_txt.write_str("-e black_editable")?;
+
+    let packages_dir = context.workspace_root.join("scripts/packages");
+
+    uv_snapshot!(context.filters(), context.install()
+        .arg("-r")
+        .arg(requirements_txt.path())
+        .current_dir(&packages_dir), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    Resolved 1 package in [TIME]
+    Downloaded 1 package in [TIME]
+    Installed 1 package in [TIME]
+     + black==0.1.0 (from file://[WORKSPACE]/scripts/packages/black_editable)
     "###
     );