fix(frontmatter): Report script manifest errors for the right line number

Author: epage

src/cargo/util/frontmatter.rs

@@ -6,8 +6,10 @@ type Span = std::ops::Range<usize>;
 pub struct ScriptSource<'s> {
     raw: &'s str,
     shebang: Option<Span>,
+    open: Option<Span>,
     info: Option<Span>,
     frontmatter: Option<Span>,
+    close: Option<Span>,
     content: Span,
 }
 
@@ -22,8 +24,10 @@ impl<'s> ScriptSource<'s> {
         let mut source = Self {
             raw,
             shebang: None,
+            open: None,
             info: None,
             frontmatter: None,
+            close: None,
             content: 0..content_end,
         };
 
@@ -61,7 +65,10 @@ impl<'s> ScriptSource<'s> {
             }
             _ => {}
         }
+        let open_start = input.current_token_start();
         let fence_pattern = input.next_slice(fence_length);
+        let open_end = input.current_token_start();
+        source.open = Some(open_start..open_end);
         let Some(info_nl) = input.find_slice("\n") else {
             anyhow::bail!("no closing `{fence_pattern}` found for frontmatter");
         };
@@ -82,7 +89,10 @@ impl<'s> ScriptSource<'s> {
         let _ = input.next_slice(frontmatter_nl.start + 1);
         let frontmatter_end = input.current_token_start();
         source.frontmatter = Some(frontmatter_start..frontmatter_end);
+        let close_start = input.current_token_start();
         let _ = input.next_slice(fence_length);
+        let close_end = input.current_token_start();
+        source.close = Some(close_start..close_end);
 
         let nl = input.find_slice("\n");
         let after_closing_fence = input.next_slice(
@@ -114,6 +124,10 @@ impl<'s> ScriptSource<'s> {
         self.shebang.clone()
     }
 
+    pub fn open_span(&self) -> Option<Span> {
+        self.open.clone()
+    }
+
     pub fn info(&self) -> Option<&'s str> {
         self.info.clone().map(|span| &self.raw[span])
     }
@@ -130,6 +144,10 @@ impl<'s> ScriptSource<'s> {
         self.frontmatter.clone()
     }
 
+    pub fn close_span(&self) -> Option<Span> {
+        self.close.clone()
+    }
+
     pub fn content(&self) -> &'s str {
         &self.raw[self.content.clone()]
     }

src/cargo/util/toml/embedded.rs

@@ -6,7 +6,7 @@ use crate::util::restricted_names;
 
 pub(super) fn expand_manifest(content: &str) -> CargoResult<String> {
     let source = ScriptSource::parse(content)?;
-    if let Some(frontmatter) = source.frontmatter() {
+    if let Some(span) = source.frontmatter_span() {
         match source.info() {
             Some("cargo") | None => {}
             Some(other) => {
@@ -22,10 +22,21 @@ pub(super) fn expand_manifest(content: &str) -> CargoResult<String> {
             }
         }
 
-        Ok(frontmatter.to_owned())
+        // Include from file start to frontmatter end when we parse the TOML to get line numbers
+        // correct and so if a TOML error says "entire file", it shows the existing content, rather
+        // than blank lines.
+        //
+        // HACK: Since frontmatter open isn't valid TOML, we insert a comment
+        let mut frontmatter = content[0..span.end].to_owned();
+        let open_span = source.open_span().unwrap();
+        frontmatter.insert(open_span.start, '#');
+        Ok(frontmatter)
     } else {
-        let frontmatter = "";
-        Ok(frontmatter.to_owned())
+        // Consider the shebang to be part of the frontmatter
+        // so if a TOML error says "entire file", it shows the existing content, rather
+        // than blank lines.
+        let span = source.shebang_span().unwrap_or(0..0);
+        Ok(content[span].to_owned())
     }
 }
 
@@ -88,11 +99,12 @@ time="0.1.25"
 fn main() {}
 "#
             ),
-            str![[r#"
+            str![[r##"
+#---cargo
 [dependencies]
 time="0.1.25"
 
-"#]]
+"##]]
         );
     }
 }

tests/testsuite/script/cargo.rs

@@ -209,9 +209,9 @@ fn main() {
         .with_stdout_data(str![""])
         .with_stderr_data(str![[r#"
 [ERROR] invalid type: integer `3`, expected a version string like "0.9.8" or a detailed dependency like { version = "0.9.8" }
- --> script.rs:2:7
+ --> script.rs:9:7
   |
-2 | bar = 3
+9 | bar = 3
   |       ^
 
 "#]])

tests/testsuite/script/rustc_fixtures/frontmatter-contains-whitespace.stderr

@@ -1,5 +1,5 @@
 [ERROR] invalid multi-line basic string, expected `/`, characters
- --> script:8:2
-  |
-8 | 4␌+
-  |  ^
+  --> script:10:2
+   |
+10 | 4␌+
+   |  ^