Fix: Support requirements.txt files which contain a remote constraint file

crates/uv-requirements-txt/src/lib.rs

@@ -349,6 +349,16 @@ impl RequirementsTxt {
                     end,
                 } => {
                     let filename = expand_env_vars(&filename);
+
+                    // Skip remote constraints when in offline mode. This is primarily for reading
+                    // lockfiles for preferences, where constraints aren't used anyway. When doing
+                    // a real compile in offline mode, remote constraints would fail during resolution.
+                    if (filename.starts_with("http://") || filename.starts_with("https://"))
+                        && client_builder.is_offline()
+                    {
+                        continue;
+                    }
+
                     let sub_file =
                         if filename.starts_with("http://") || filename.starts_with("https://") {
                             PathBuf::from(filename.as_ref())

crates/uv/tests/it/pip_compile.rs

@@ -17850,3 +17850,88 @@ fn credentials_from_subdirectory() -> Result<()> {
 
     Ok(())
 }
+
+/// Test that recompiling with a remote constraint in the output file works.
+/// This reproduces a bug where uv would fail with "Network connectivity is disabled"
+/// when trying to recompile a requirements.txt that contains a remote --constraint directive.
+/// This is required for AWS MWAA workflows where the constraint must be in the output file.
+#[tokio::test]
+async fn compile_with_remote_constraint_in_output() -> Result<()> {
+    let context = TestContext::new("3.12");
+    let server = MockServer::start().await;
+
+    // Create a simple constraints file on the mock server
+    let constraints_content = "idna==3.3\n";
+    Mock::given(method("GET"))
+        .and(path("/constraints.txt"))
+        .respond_with(ResponseTemplate::new(200).set_body_raw(constraints_content, "text/plain"))
+        .mount(&server)
+        .await;
+
+    let requirements_in = context.temp_dir.child("requirements.in");
+    requirements_in.write_str(&format!(
+        "--constraint \"{}/constraints.txt\"\nanyio==3.7.0",
+        server.uri()
+    ))?;
+
+    let requirements_txt = context.temp_dir.child("requirements.txt");
+
+    // First compilation - should work
+    uv_snapshot!(context.filters(), context.pip_compile()
+        .arg("requirements.in")
+        .arg("--output-file")
+        .arg("requirements.txt"), @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 --output-file requirements.txt
+    anyio==3.7.0
+        # via -r requirements.in
+    idna==3.3
+        # via
+        #   -c http://[LOCALHOST]/constraints.txt
+        #   anyio
+    sniffio==1.3.1
+        # via anyio
+
+    ----- stderr -----
+    Resolved 3 packages in [TIME]
+    "###
+    );
+
+    // Append the constraint directive to the output file (simulating AWS MWAA requirement)
+    let mut output_content = fs_err::read_to_string(&requirements_txt)?;
+    output_content.push_str("--constraint \"");
+    output_content.push_str(&server.uri());
+    output_content.push_str("/constraints.txt\"\n");
+    fs_err::write(&requirements_txt, output_content)?;
+
+    // Second compilation - should also work (this is where the bug occurs)
+    // The bug is that uv tries to parse the constraint in offline mode when reading
+    // the output file for preferences, and fails with "Network connectivity is disabled"
+    uv_snapshot!(context.filters(), context.pip_compile()
+        .arg("requirements.in")
+        .arg("--output-file")
+        .arg("requirements.txt"), @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 --output-file requirements.txt
+    anyio==3.7.0
+        # via -r requirements.in
+    idna==3.3
+        # via
+        #   -c http://[LOCALHOST]/constraints.txt
+        #   anyio
+    sniffio==1.3.1
+        # via anyio
+
+    ----- stderr -----
+    Resolved 3 packages in [TIME]
+    "###
+    );
+
+    Ok(())
+}