Allow reading `--with-requirements` from stdin in `uv add` and `uv run` (#10447)

For some reason this was banned when originally added (I did not see
discussion about it). I think it's fine to allow. With `uv run`, there's
a bit of nuance because we also allow the script to be read from stdin.

crates/uv/src/commands/project/add.rs

@@ -98,11 +98,6 @@ pub(crate) async fn add(
             RequirementsSource::SetupCfg(_) => {
                 bail!("Adding requirements from a `setup.cfg` is not supported in `uv add`");
             }
-            RequirementsSource::RequirementsTxt(path) => {
-                if path == Path::new("-") {
-                    bail!("Reading requirements from stdin is not supported in `uv add`");
-                }
-            }
             _ => {}
         }
     }

crates/uv/src/commands/project/run.rs

@@ -93,6 +93,7 @@ pub(crate) async fn run(
 ) -> anyhow::Result<ExitStatus> {
     // These cases seem quite complex because (in theory) they should change the "current package".
     // Let's ban them entirely for now.
+    let mut requirements_from_stdin: bool = false;
     for source in &requirements {
         match source {
             RequirementsSource::PyprojectToml(_) => {
@@ -106,13 +107,22 @@ pub(crate) async fn run(
             }
             RequirementsSource::RequirementsTxt(path) => {
                 if path == Path::new("-") {
-                    bail!("Reading requirements from stdin is not supported in `uv run`");
+                    requirements_from_stdin = true;
                 }
             }
             _ => {}
         }
     }
 
+    // Fail early if stdin is used for multiple purposes.
+    if matches!(
+        command,
+        Some(RunCommand::PythonStdin(..) | RunCommand::PythonGuiStdin(..))
+    ) && requirements_from_stdin
+    {
+        bail!("Cannot read both requirements file and script from stdin");
+    }
+
     // Initialize any shared state.
     let state = SharedState::default();
 
@@ -169,6 +179,9 @@ pub(crate) async fn run(
                 )?;
             }
             Pep723Item::Stdin(_) => {
+                if requirements_from_stdin {
+                    bail!("Cannot read both requirements file and script from stdin");
+                }
                 writeln!(
                     printer.stderr(),
                     "Reading inline script metadata from `{}`",

crates/uv/tests/it/edit.rs

@@ -1,3 +1,5 @@
+#![allow(clippy::disallowed_types)]
+
 use anyhow::Result;
 use assert_cmd::assert::OutputAssertExt;
 use assert_fs::prelude::*;
@@ -4611,6 +4613,17 @@ fn add_requirements_file() -> Result<()> {
         );
     });
 
+    // Passing stdin should succeed
+    uv_snapshot!(context.filters(), context.add().arg("-r").arg("-").stdin(std::fs::File::open(requirements_txt)?), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    Resolved [N] packages in [TIME]
+    Audited [N] packages in [TIME]
+    "###);
+
     // Passing a `setup.py` should fail.
     uv_snapshot!(context.filters(), context.add().arg("-r").arg("setup.py"), @r###"
     success: false

crates/uv/tests/it/run.rs

@@ -2124,19 +2124,51 @@ fn run_requirements_txt() -> Result<()> {
      + sniffio==1.3.1
     "###);
 
-    // But reject `-` as a requirements file.
+    // Allow `-` for stdin.
     uv_snapshot!(context.filters(), context.run()
         .arg("--with-requirements")
         .arg("-")
         .arg("--with")
         .arg("iniconfig")
-        .arg("main.py"), @r###"
+        .arg("main.py")
+        .stdin(std::fs::File::open(&requirements_txt)?), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    Resolved 6 packages in [TIME]
+    Audited 4 packages in [TIME]
+    Resolved 2 packages in [TIME]
+    "###);
+
+    // But not in combination with reading the script from stdin
+    uv_snapshot!(context.filters(), context.run()
+        .arg("--with-requirements")
+        .arg("-")
+        // The script to run
+        .arg("-")
+        .stdin(std::fs::File::open(&requirements_txt)?), @r###"
     success: false
     exit_code: 2
     ----- stdout -----
 
     ----- stderr -----
-    error: Reading requirements from stdin is not supported in `uv run`
+    error: Cannot read both requirements file and script from stdin
+    "###);
+
+    uv_snapshot!(context.filters(), context.run()
+        .arg("--with-requirements")
+        .arg("-")
+        .arg("--script")
+        .arg("-")
+        .stdin(std::fs::File::open(&requirements_txt)?), @r###"
+    success: false
+    exit_code: 2
+    ----- stdout -----
+
+    ----- stderr -----
+    error: Cannot read both requirements file and script from stdin
     "###);
 
     Ok(())