Error on missing argument in `requirements.txt` (#12354)

Closes https://github.com/astral-sh/uv/issues/12348.

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

@@ -522,7 +522,7 @@ fn parse_entry(
 
     let start = s.cursor();
     Ok(Some(if s.eat_if("-r") || s.eat_if("--requirement") {
-        let filename = parse_value(content, s, |c: char| !is_terminal(c))?;
+        let filename = parse_value("--requirement", content, s, |c: char| !is_terminal(c))?;
         let filename = unquote(filename)
             .ok()
             .flatten()
@@ -534,7 +534,7 @@ fn parse_entry(
             end,
         }
     } else if s.eat_if("-c") || s.eat_if("--constraint") {
-        let filename = parse_value(content, s, |c: char| !is_terminal(c))?;
+        let filename = parse_value("--constraint", content, s, |c: char| !is_terminal(c))?;
         let filename = unquote(filename)
             .ok()
             .flatten()
@@ -581,7 +581,7 @@ fn parse_entry(
             hashes,
         })
     } else if s.eat_if("-i") || s.eat_if("--index-url") {
-        let given = parse_value(content, s, |c: char| !is_terminal(c))?;
+        let given = parse_value("--index-url", content, s, |c: char| !is_terminal(c))?;
         let given = unquote(given)
             .ok()
             .flatten()
@@ -612,7 +612,7 @@ fn parse_entry(
         };
         RequirementsTxtStatement::IndexUrl(url.with_given(given))
     } else if s.eat_if("--extra-index-url") {
-        let given = parse_value(content, s, |c: char| !is_terminal(c))?;
+        let given = parse_value("--extra-index-url", content, s, |c: char| !is_terminal(c))?;
         let given = unquote(given)
             .ok()
             .flatten()
@@ -645,7 +645,7 @@ fn parse_entry(
     } else if s.eat_if("--no-index") {
         RequirementsTxtStatement::NoIndex
     } else if s.eat_if("--find-links") || s.eat_if("-f") {
-        let given = parse_value(content, s, |c: char| !is_terminal(c))?;
+        let given = parse_value("--find-links", content, s, |c: char| !is_terminal(c))?;
         let given = unquote(given)
             .ok()
             .flatten()
@@ -676,7 +676,7 @@ fn parse_entry(
         };
         RequirementsTxtStatement::FindLinks(url.with_given(given))
     } else if s.eat_if("--no-binary") {
-        let given = parse_value(content, s, |c: char| !is_terminal(c))?;
+        let given = parse_value("--no-binary", content, s, |c: char| !is_terminal(c))?;
         let given = unquote(given)
             .ok()
             .flatten()
@@ -692,7 +692,7 @@ fn parse_entry(
         })?;
         RequirementsTxtStatement::NoBinary(NoBinary::from_pip_arg(specifier))
     } else if s.eat_if("--only-binary") {
-        let given = parse_value(content, s, |c: char| !is_terminal(c))?;
+        let given = parse_value("--only-binary", content, s, |c: char| !is_terminal(c))?;
         let given = unquote(given)
             .ok()
             .flatten()
@@ -878,14 +878,14 @@ fn parse_hashes(content: &str, s: &mut Scanner) -> Result<Vec<String>, Requireme
             column,
         });
     }
-    let hash = parse_value(content, s, |c: char| !c.is_whitespace())?;
+    let hash = parse_value("--hash", content, s, |c: char| !c.is_whitespace())?;
     hashes.push(hash.to_string());
     loop {
         eat_wrappable_whitespace(s);
         if !s.eat_if("--hash") {
             break;
         }
-        let hash = parse_value(content, s, |c: char| !c.is_whitespace())?;
+        let hash = parse_value("--hash", content, s, |c: char| !c.is_whitespace())?;
         hashes.push(hash.to_string());
     }
     Ok(hashes)
@@ -893,25 +893,37 @@ fn parse_hashes(content: &str, s: &mut Scanner) -> Result<Vec<String>, Requireme
 
 /// In `-<key>=<value>` or `-<key> value`, this parses the part after the key
 fn parse_value<'a, T>(
+    option: &str,
     content: &str,
     s: &mut Scanner<'a>,
     while_pattern: impl Pattern<T>,
 ) -> Result<&'a str, RequirementsTxtParserError> {
-    if s.eat_if('=') {
+    let value = if s.eat_if('=') {
         // Explicit equals sign.
-        Ok(s.eat_while(while_pattern).trim_end())
+        s.eat_while(while_pattern).trim_end()
     } else if s.eat_if(char::is_whitespace) {
         // Key and value are separated by whitespace instead.
         s.eat_whitespace();
-        Ok(s.eat_while(while_pattern).trim_end())
+        s.eat_while(while_pattern).trim_end()
     } else {
         let (line, column) = calculate_row_column(content, s.cursor());
-        Err(RequirementsTxtParserError::Parser {
+        return Err(RequirementsTxtParserError::Parser {
             message: format!("Expected '=' or whitespace, found {:?}", s.peek()),
             line,
             column,
-        })
+        });
+    };
+
+    if value.is_empty() {
+        let (line, column) = calculate_row_column(content, s.cursor());
+        return Err(RequirementsTxtParserError::Parser {
+            message: format!("`{option}` must be followed by an argument"),
+            line,
+            column,
+        });
     }
+
+    Ok(value)
 }
 
 /// Fetch the contents of a URL and return them as a string.
@@ -1780,6 +1792,35 @@ mod test {
         Ok(())
     }
 
+    #[tokio::test]
+    async fn missing_value() -> Result<()> {
+        let temp_dir = assert_fs::TempDir::new()?;
+        let requirements_txt = temp_dir.child("requirements.txt");
+        requirements_txt.write_str(indoc! {"
+            flask
+            --no-binary
+        "})?;
+
+        let error = RequirementsTxt::parse(
+            requirements_txt.path(),
+            temp_dir.path(),
+            &BaseClientBuilder::new(),
+        )
+        .await
+        .unwrap_err();
+        let errors = anyhow::Error::new(error).chain().join("\n");
+
+        let requirement_txt = regex::escape(&requirements_txt.path().user_display().to_string());
+        let filters = vec![(requirement_txt.as_str(), "<REQUIREMENTS_TXT>")];
+        insta::with_settings!({
+            filters => filters
+        }, {
+            insta::assert_snapshot!(errors, @"`--no-binary` must be followed by an argument at <REQUIREMENTS_TXT>:3:1");
+        });
+
+        Ok(())
+    }
+
     #[tokio::test]
     async fn missing_r() -> Result<()> {
         let temp_dir = assert_fs::TempDir::new()?;