Warn-and-ignore for unsupported requirements.txt options (#10420)

## Summary

Closes https://github.com/astral-sh/uv/issues/10366.

Cargo.lock

@@ -5485,6 +5485,7 @@ dependencies = [
  "uv-normalize",
  "uv-pep508",
  "uv-pypi-types",
+ "uv-warnings",
 ]
 
 [[package]]

crates/uv-requirements-txt/Cargo.toml

@@ -16,13 +16,14 @@ doctest = false
 workspace = true
 
 [dependencies]
-uv-distribution-types = { workspace = true }
-uv-pep508 = { workspace = true }
-uv-pypi-types = { workspace = true }
 uv-client = { workspace = true }
+uv-configuration = { workspace = true }
+uv-distribution-types = { workspace = true }
 uv-fs = { workspace = true }
 uv-normalize = { workspace = true }
-uv-configuration = { workspace = true }
+uv-pep508 = { workspace = true }
+uv-pypi-types = { workspace = true }
+uv-warnings = { workspace = true }
 
 fs-err = { workspace = true }
 regex = { workspace = true }

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

@@ -88,6 +88,8 @@ enum RequirementsTxtStatement {
     NoBinary(NoBinary),
     /// `--only-binary`
     OnlyBinary(NoBuild),
+    /// An unsupported option (e.g., `--trusted-host`).
+    UnsupportedOption(UnsupportedOption),
 }
 
 /// A [Requirement] with additional metadata from the `requirements.txt`, currently only hashes but in
@@ -384,6 +386,28 @@ impl RequirementsTxt {
                 RequirementsTxtStatement::OnlyBinary(only_binary) => {
                     data.only_binary.extend(only_binary);
                 }
+                RequirementsTxtStatement::UnsupportedOption(flag) => {
+                    if requirements_txt == Path::new("-") {
+                        if flag.cli() {
+                            uv_warnings::warn_user!("Ignoring unsupported option from stdin: `{flag}` (hint: pass `{flag}` on the command line instead)", flag = flag.green());
+                        } else {
+                            uv_warnings::warn_user!(
+                                "Ignoring unsupported option from stdin: `{flag}`",
+                                flag = flag.green()
+                            );
+                        }
+                    } else {
+                        if flag.cli() {
+                            uv_warnings::warn_user!("Ignoring unsupported option in `{path}`: `{flag}` (hint: pass `{flag}` on the command line instead)", path = requirements_txt.user_display().cyan(), flag = flag.green());
+                        } else {
+                            uv_warnings::warn_user!(
+                                "Ignoring unsupported option in `{path}`: `{flag}`",
+                                path = requirements_txt.user_display().cyan(),
+                                flag = flag.green()
+                            );
+                        }
+                    }
+                }
             }
         }
         Ok(data)
@@ -416,15 +440,70 @@ impl RequirementsTxt {
     }
 }
 
+/// An unsupported option (e.g., `--trusted-host`).
+///
+/// See: <https://pip.pypa.io/en/stable/reference/requirements-file-format/#global-options>
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+enum UnsupportedOption {
+    PreferBinary,
+    RequireHashes,
+    Pre,
+    TrustedHost,
+    UseFeature,
+}
+
+impl UnsupportedOption {
+    /// The name of the unsupported option.
+    fn name(self) -> &'static str {
+        match self {
+            UnsupportedOption::PreferBinary => "--prefer-binary",
+            UnsupportedOption::RequireHashes => "--require-hashes",
+            UnsupportedOption::Pre => "--pre",
+            UnsupportedOption::TrustedHost => "--trusted-host",
+            UnsupportedOption::UseFeature => "--use-feature",
+        }
+    }
+
+    /// Returns `true` if the option is supported on the CLI.
+    fn cli(self) -> bool {
+        match self {
+            UnsupportedOption::PreferBinary => false,
+            UnsupportedOption::RequireHashes => true,
+            UnsupportedOption::Pre => true,
+            UnsupportedOption::TrustedHost => true,
+            UnsupportedOption::UseFeature => false,
+        }
+    }
+
+    /// Returns an iterator over all unsupported options.
+    fn iter() -> impl Iterator<Item = UnsupportedOption> {
+        [
+            UnsupportedOption::PreferBinary,
+            UnsupportedOption::RequireHashes,
+            UnsupportedOption::Pre,
+            UnsupportedOption::TrustedHost,
+            UnsupportedOption::UseFeature,
+        ]
+        .iter()
+        .copied()
+    }
+}
+
+impl Display for UnsupportedOption {
+    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+        write!(f, "{}", self.name())
+    }
+}
+
 /// Returns `true` if the character is a newline or a comment character.
 const fn is_terminal(c: char) -> bool {
     matches!(c, '\n' | '\r' | '#')
 }
 
-/// Parse a single entry, that is a requirement, an inclusion or a comment line
+/// Parse a single entry, that is a requirement, an inclusion or a comment line.
 ///
-/// Consumes all preceding trivia (whitespace and comments). If it returns None, we've reached
-/// the end of file
+/// Consumes all preceding trivia (whitespace and comments). If it returns `None`, we've reached
+/// the end of file.
 fn parse_entry(
     s: &mut Scanner,
     content: &str,
@@ -595,14 +674,20 @@ fn parse_entry(
             hashes,
         })
     } else if let Some(char) = s.peek() {
-        let (line, column) = calculate_row_column(content, s.cursor());
-        return Err(RequirementsTxtParserError::Parser {
-            message: format!(
-                "Unexpected '{char}', expected '-c', '-e', '-r' or the start of a requirement"
-            ),
-            line,
-            column,
-        });
+        // Identify an unsupported option, like `--trusted-host`.
+        if let Some(option) = UnsupportedOption::iter().find(|option| s.eat_if(option.name())) {
+            s.eat_while(|c: char| !is_terminal(c));
+            RequirementsTxtStatement::UnsupportedOption(option)
+        } else {
+            let (line, column) = calculate_row_column(content, s.cursor());
+            return Err(RequirementsTxtParserError::Parser {
+                message: format!(
+                    "Unexpected '{char}', expected '-c', '-e', '-r' or the start of a requirement"
+                ),
+                line,
+                column,
+            });
+        }
     } else {
         // EOF
         return Ok(None);

crates/uv/tests/it/pip_install.rs

@@ -486,6 +486,39 @@ fn install_requirements_txt() -> Result<()> {
     Ok(())
 }
 
+/// Warn (but don't fail) when unsupported flags are set in the `requirements.txt`.
+#[test]
+fn install_unsupported_flag() -> Result<()> {
+    let context = TestContext::new("3.12");
+
+    let requirements_txt = context.temp_dir.child("requirements.txt");
+    requirements_txt.write_str(indoc! {r"
+        --pre
+        --prefer-binary :all:
+        iniconfig
+    "})?;
+
+    uv_snapshot!(context.pip_install()
+        .arg("-r")
+        .arg("requirements.txt")
+        .arg("--strict"), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    warning: Ignoring unsupported option in `requirements.txt`: `--pre` (hint: pass `--pre` on the command line instead)
+    warning: Ignoring unsupported option in `requirements.txt`: `--prefer-binary`
+    Resolved 1 package in [TIME]
+    Prepared 1 package in [TIME]
+    Installed 1 package in [TIME]
+     + iniconfig==2.0.0
+    "###
+    );
+
+    Ok(())
+}
+
 /// Install a requirements file with pins that conflict
 ///
 /// This is likely to occur in the real world when compiled on one platform then installed on another.