Implement Span::line() and Span::column() for proc-macro server

Add proper line/column resolution for proc-macro spans via a callback
mechanism. Previously these methods returned hardcoded 1 values.

The implementation adds:
- SubRequest::LineColumn and SubResponse::LineColumnResult to the
  bidirectional protocol
- ProcMacroClientInterface::line_column() method
- Callback handling in load-cargo using LineIndex
- Server implementation in RaSpanServer that uses the callback
- a test for Span::line() and Span::column() in proc-macro server

Add fn_like_span_line_column test proc-macro that exercises the new
line/column API, and a corresponding test with a mock callback.

Author: tilladam

Cargo.lock

@@ -554,21 +554,31 @@ impl ProcMacroExpander for Expander {
                 Ok(SubResponse::LocalFilePathResult { name })
             }
             SubRequest::SourceText { file_id, ast_id, start, end } => {
-                let ast_id = span::ErasedFileAstId::from_raw(ast_id);
-                let editioned_file_id = span::EditionedFileId::from_raw(file_id);
-                let span = Span {
-                    range: TextRange::new(TextSize::from(start), TextSize::from(end)),
-                    anchor: SpanAnchor { file_id: editioned_file_id, ast_id },
-                    ctx: SyntaxContext::root(editioned_file_id.edition()),
-                };
-                let range = db.resolve_span(span);
+                let range = resolve_sub_span(
+                    db,
+                    file_id,
+                    ast_id,
+                    TextRange::new(TextSize::from(start), TextSize::from(end)),
+                );
                 let source = db.file_text(range.file_id.file_id(db)).text(db);
                 let text = source
                     .get(usize::from(range.range.start())..usize::from(range.range.end()))
                     .map(ToOwned::to_owned);
 
                 Ok(SubResponse::SourceTextResult { text })
             }
+            SubRequest::LineColumn { file_id, ast_id, offset } => {
+                let range =
+                    resolve_sub_span(db, file_id, ast_id, TextRange::empty(TextSize::from(offset)));
+                let source = db.file_text(range.file_id.file_id(db)).text(db);
+                let line_index = ide_db::line_index::LineIndex::new(source);
+                let (line, column) = line_index
+                    .try_line_col(range.range.start())
+                    .map(|lc| (lc.line as u32 + 1, lc.col as u32 + 1))
+                    .unwrap_or((1, 1));
+                // proc_macro::Span line/column are 1-based
+                Ok(SubResponse::LineColumnResult { line, column })
+            }
             SubRequest::FilePath { file_id } => {
                 let file_id = FileId::from_raw(file_id);
                 let source_root_id = db.file_source_root(file_id).source_root_id(db);
@@ -603,6 +613,22 @@ impl ProcMacroExpander for Expander {
     }
 }
 
+fn resolve_sub_span(
+    db: &dyn ExpandDatabase,
+    file_id: u32,
+    ast_id: u32,
+    range: TextRange,
+) -> hir_expand::FileRange {
+    let ast_id = span::ErasedFileAstId::from_raw(ast_id);
+    let editioned_file_id = span::EditionedFileId::from_raw(file_id);
+    let span = Span {
+        range,
+        anchor: SpanAnchor { file_id: editioned_file_id, ast_id },
+        ctx: SyntaxContext::root(editioned_file_id.edition()),
+    };
+    db.resolve_span(span)
+}
+
 #[cfg(test)]
 mod tests {
     use ide_db::base_db::RootQueryDb;

crates/load-cargo/src/lib.rs

@@ -13,13 +13,25 @@ pub enum SubRequest {
     FilePath { file_id: u32 },
     SourceText { file_id: u32, ast_id: u32, start: u32, end: u32 },
     LocalFilePath { file_id: u32 },
+    LineColumn { file_id: u32, ast_id: u32, offset: u32 },
 }
 
 #[derive(Debug, Serialize, Deserialize)]
 pub enum SubResponse {
-    FilePathResult { name: String },
-    SourceTextResult { text: Option<String> },
-    LocalFilePathResult { name: Option<String> },
+    FilePathResult {
+        name: String,
+    },
+    SourceTextResult {
+        text: Option<String>,
+    },
+    LocalFilePathResult {
+        name: Option<String>,
+    },
+    /// Line and column are 1-based.
+    LineColumnResult {
+        line: u32,
+        column: u32,
+    },
 }
 
 #[derive(Debug, Serialize, Deserialize)]

crates/proc-macro-api/src/bidirectional_protocol/msg.rs

@@ -220,6 +220,20 @@ impl<C: Codec> proc_macro_srv::ProcMacroClientInterface for ProcMacroClientHandl
             _ => None,
         }
     }
+
+    fn line_column(&mut self, span: proc_macro_srv::span::Span) -> Option<(u32, u32)> {
+        let proc_macro_srv::span::Span { range, anchor, ctx: _ } = span;
+        match self.roundtrip(bidirectional::SubRequest::LineColumn {
+            file_id: anchor.file_id.as_u32(),
+            ast_id: anchor.ast_id.into_raw(),
+            offset: range.start().into(),
+        }) {
+            Some(bidirectional::BidirectionalMessage::SubResponse(
+                bidirectional::SubResponse::LineColumnResult { line, column },
+            )) => Some((line, column)),
+            _ => None,
+        }
+    }
 }
 
 fn handle_expand_ra<C: Codec>(

crates/proc-macro-srv-cli/src/main_loop.rs

@@ -31,6 +31,7 @@ libc.workspace = true
 
 [dev-dependencies]
 expect-test.workspace = true
+line-index.workspace = true
 
 # used as proc macro test targets
 proc-macro-test.path = "./proc-macro-test"

crates/proc-macro-srv/Cargo.toml

@@ -79,6 +79,16 @@ pub fn fn_like_span_ops(args: TokenStream) -> TokenStream {
     TokenStream::from_iter(vec![first, second, third])
 }
 
+/// Returns the line and column of the first token's span as two integer literals.
+#[proc_macro]
+pub fn fn_like_span_line_column(args: TokenStream) -> TokenStream {
+    let first = args.into_iter().next().unwrap();
+    let span = first.span();
+    let line = Literal::usize_unsuffixed(span.line());
+    let column = Literal::usize_unsuffixed(span.column());
+    TokenStream::from_iter(vec![TokenTree::Literal(line), TokenTree::Literal(column)])
+}
+
 #[proc_macro_attribute]
 pub fn attr_noop(_args: TokenStream, item: TokenStream) -> TokenStream {
     item

crates/proc-macro-srv/proc-macro-test/imp/src/lib.rs

@@ -98,6 +98,8 @@ pub trait ProcMacroClientInterface {
     fn file(&mut self, file_id: span::FileId) -> String;
     fn source_text(&mut self, span: Span) -> Option<String>;
     fn local_file(&mut self, file_id: span::FileId) -> Option<String>;
+    /// Line and column are 1-based.
+    fn line_column(&mut self, span: Span) -> Option<(u32, u32)>;
 }
 
 const EXPANDER_STACK_SIZE: usize = 8 * 1024 * 1024;

crates/proc-macro-srv/src/lib.rs

@@ -257,14 +257,12 @@ impl server::Span for RaSpanServer<'_> {
         Span { range: TextRange::empty(span.range.start()), ..span }
     }
 
-    fn line(&mut self, _span: Self::Span) -> usize {
-        // FIXME requires db to resolve line index, THIS IS NOT INCREMENTAL
-        1
+    fn line(&mut self, span: Self::Span) -> usize {
+        self.callback.as_mut().and_then(|cb| cb.line_column(span)).map_or(1, |(l, _)| l as usize)
     }
 
-    fn column(&mut self, _span: Self::Span) -> usize {
-        // FIXME requires db to resolve line index, THIS IS NOT INCREMENTAL
-        1
+    fn column(&mut self, span: Self::Span) -> usize {
+        self.callback.as_mut().and_then(|cb| cb.line_column(span)).map_or(1, |(_, c)| c as usize)
     }
 }
 

crates/proc-macro-srv/src/server_impl/rust_analyzer_span.rs

@@ -703,6 +703,7 @@ fn list_test_macros() {
         fn_like_mk_idents [Bang]
         fn_like_span_join [Bang]
         fn_like_span_ops [Bang]
+        fn_like_span_line_column [Bang]
         attr_noop [Attr]
         attr_panic [Attr]
         attr_error [Attr]
@@ -712,3 +713,17 @@ fn list_test_macros() {
         DeriveError [CustomDerive]"#]]
     .assert_eq(&res);
 }
+
+#[test]
+fn test_fn_like_span_line_column() {
+    assert_expand_with_callback(
+        "fn_like_span_line_column",
+        // Input text with known position: "hello" starts at offset 1 (line 2, column 1 in 1-based)
+        "
+hello",
+        expect![[r#"
+            LITER 42:Root[0000, 0]@0..100#ROOT2024 Integer 2
+            LITER 42:Root[0000, 0]@0..100#ROOT2024 Integer 1
+        "#]],
+    );
+}

crates/proc-macro-srv/src/tests/mod.rs

@@ -6,7 +6,8 @@ use span::{
 };
 
 use crate::{
-    EnvSnapshot, ProcMacroSrv, SpanId, dylib, proc_macro_test_dylib_path, token_stream::TokenStream,
+    EnvSnapshot, ProcMacroClientInterface, ProcMacroSrv, SpanId, dylib, proc_macro_test_dylib_path,
+    token_stream::TokenStream,
 };
 
 fn parse_string(call_site: SpanId, src: &str) -> TokenStream<SpanId> {
@@ -109,3 +110,66 @@ pub(crate) fn list() -> Vec<String> {
     let res = srv.list_macros(&dylib_path).unwrap();
     res.into_iter().map(|(name, kind)| format!("{name} [{kind:?}]")).collect()
 }
+
+/// A mock callback for testing that computes line/column from the input text.
+struct MockCallback<'a> {
+    text: &'a str,
+}
+
+impl ProcMacroClientInterface for MockCallback<'_> {
+    fn source_text(&mut self, span: Span) -> Option<String> {
+        self.text
+            .get(usize::from(span.range.start())..usize::from(span.range.end()))
+            .map(ToOwned::to_owned)
+    }
+
+    fn file(&mut self, _file_id: FileId) -> String {
+        String::new()
+    }
+
+    fn local_file(&mut self, _file_id: FileId) -> Option<String> {
+        None
+    }
+
+    fn line_column(&mut self, span: Span) -> Option<(u32, u32)> {
+        let line_index = line_index::LineIndex::new(self.text);
+        let line_col = line_index.try_line_col(span.range.start())?;
+        // proc_macro uses 1-based line/column
+        Some((line_col.line as u32 + 1, line_col.col as u32 + 1))
+    }
+}
+
+pub fn assert_expand_with_callback(
+    macro_name: &str,
+    #[rust_analyzer::rust_fixture] ra_fixture: &str,
+    expect_spanned: Expect,
+) {
+    let path = proc_macro_test_dylib_path();
+    let expander = dylib::Expander::new(&temp_dir::TempDir::new().unwrap(), &path).unwrap();
+
+    let def_site = Span {
+        range: TextRange::new(0.into(), 150.into()),
+        anchor: SpanAnchor {
+            file_id: EditionedFileId::current_edition(FileId::from_raw(41)),
+            ast_id: ROOT_ERASED_FILE_AST_ID,
+        },
+        ctx: SyntaxContext::root(span::Edition::CURRENT),
+    };
+    let call_site = Span {
+        range: TextRange::new(0.into(), 100.into()),
+        anchor: SpanAnchor {
+            file_id: EditionedFileId::current_edition(FileId::from_raw(42)),
+            ast_id: ROOT_ERASED_FILE_AST_ID,
+        },
+        ctx: SyntaxContext::root(span::Edition::CURRENT),
+    };
+    let mixed_site = call_site;
+
+    let fixture = parse_string_spanned(call_site.anchor, call_site.ctx, ra_fixture);
+
+    let mut callback = MockCallback { text: ra_fixture };
+    let res = expander
+        .expand(macro_name, fixture, None, def_site, call_site, mixed_site, Some(&mut callback))
+        .unwrap();
+    expect_spanned.assert_eq(&format!("{res:?}"));
+}