From 9d0308febcff56fa2ac8f4e62e1738c570ed54f4 Mon Sep 17 00:00:00 2001
From: Hong Jiarong <me@jrhim.com>
Date: Mon, 15 Dec 2025 21:28:57 +0800
Subject: [PATCH] fix(lint): refine dead-code exported handling

- Treat module-level exported symbols as exported when configured

- De-duplicate decl diagnostics across scopes

- Replace docstring suppression with a softer hint
---
 crates/tinymist-lint/src/dead_code.rs         | 28 ++++++++++---
 .../tinymist-lint/src/dead_code/diagnostic.rs | 39 +++++--------------
 crates/tinymist-lint/src/lib.rs               |  5 +++
 3 files changed, 37 insertions(+), 35 deletions(-)

diff --git a/crates/tinymist-lint/src/dead_code.rs b/crates/tinymist-lint/src/dead_code.rs
index 7d5a1d605..668389650 100644
--- a/crates/tinymist-lint/src/dead_code.rs
+++ b/crates/tinymist-lint/src/dead_code.rs
@@ -68,20 +68,31 @@ pub fn check_dead_code(
         module_used_decls,
     } = compute_import_usage(&definitions, ei);
 
-    let mut seen_module_aliases = HashSet::new();
+    let mut seen_decls = HashSet::new();
 
     for def_info in definitions {
-        if matches!(def_info.decl.as_ref(), Decl::ModuleAlias(_))
-            && !seen_module_aliases.insert(def_info.decl.clone())
+        let def_info = if config.check_exported
+            && matches!(def_info.scope, DefScope::File)
+            && is_exported_symbol_candidate(def_info.decl.as_ref())
+            && ei.is_exported(&def_info.decl)
         {
-            continue;
-        }
+            DefInfo {
+                scope: DefScope::Exported,
+                ..def_info
+            }
+        } else {
+            def_info
+        };
+
         if shadowed.contains(&def_info.decl) {
             continue;
         }
         if should_skip_definition(&def_info, config) {
             continue;
         }
+        if !seen_decls.insert(def_info.decl.clone()) {
+            continue;
+        }
 
         let is_unused = match def_info.decl.as_ref() {
             Decl::Import(_) | Decl::ImportAlias(_) => !used.contains(&def_info.decl),
@@ -213,6 +224,13 @@ fn compute_import_usage(definitions: &[DefInfo], ei: &ExprInfo) -> ImportUsageIn
     }
 }
 
+fn is_exported_symbol_candidate(decl: &Decl) -> bool {
+    matches!(
+        decl,
+        Decl::Func(_) | Decl::Var(_) | Decl::Module(_) | Decl::Closure(_)
+    )
+}
+
 fn is_wildcard_module_import_decl(ei: &ExprInfo, decl: &Interned<Decl>) -> bool {
     let span = decl.span();
     if span.is_detached() {
diff --git a/crates/tinymist-lint/src/dead_code/diagnostic.rs b/crates/tinymist-lint/src/dead_code/diagnostic.rs
index 47ac8554f..2f849e94b 100644
--- a/crates/tinymist-lint/src/dead_code/diagnostic.rs
+++ b/crates/tinymist-lint/src/dead_code/diagnostic.rs
@@ -6,11 +6,11 @@
 use tinymist_analysis::syntax::{Decl, DefKind, ExprInfo};
 use tinymist_project::LspWorld;
 use typst::diag::{SourceDiagnostic, eco_format};
-use typst::syntax::ast::AstNode;
-use typst::syntax::{LinkedNode, Span, ast};
 
 use super::collector::{DefInfo, DefScope};
 
+use crate::DOCUMENTED_EXPORTED_FUNCTION_HINT;
+
 /// Generates a diagnostic for an unused definition.
 ///
 /// Creates a warning with contextual information about the unused symbol,
@@ -51,14 +51,12 @@ pub fn generate_diagnostic(
     }
 
     // Create the base diagnostic
-    let highlight_span = binding_span(def_info, ei).unwrap_or(def_info.span);
-
     let mut diag = if is_module_import {
-        SourceDiagnostic::warning(highlight_span, eco_format!("unused module import"))
+        SourceDiagnostic::warning(def_info.span, eco_format!("unused module import"))
     } else if is_import_item {
-        SourceDiagnostic::warning(highlight_span, eco_format!("unused import: `{name}`"))
+        SourceDiagnostic::warning(def_info.span, eco_format!("unused import: `{name}`"))
     } else {
-        SourceDiagnostic::warning(highlight_span, eco_format!("unused {kind_str}: `{name}`"))
+        SourceDiagnostic::warning(def_info.span, eco_format!("unused {kind_str}: `{name}`"))
     };
 
     // Add helpful hints based on the scope and kind
@@ -84,12 +82,13 @@ pub fn generate_diagnostic(
 
     // Add kind-specific hints
     if let DefKind::Function = def_info.kind {
-        // Check if there's a docstring - documented functions might be intentional API
         if matches!(def_info.scope, DefScope::Exported)
             && ei.docstrings.contains_key(&def_info.decl)
         {
-            // Reduce severity for documented functions (they might be public API)
-            return None;
+            diag = diag.with_hint(DOCUMENTED_EXPORTED_FUNCTION_HINT);
+            diag = diag.with_hint(
+                "if this is intended public API, you can ignore this diagnostic; otherwise consider removing it",
+            );
         }
     }
 
@@ -99,23 +98,3 @@ pub fn generate_diagnostic(
 
     Some(diag)
 }
-
-fn binding_span(def_info: &DefInfo, ei: &ExprInfo) -> Option<Span> {
-    if !matches!(def_info.kind, DefKind::Variable | DefKind::Constant) {
-        return None;
-    }
-    if !matches!(def_info.scope, DefScope::File | DefScope::Local) {
-        return None;
-    }
-
-    let node = LinkedNode::new(ei.source.root()).find(def_info.span)?;
-    let mut current = Some(node);
-    while let Some(node) = current {
-        if let Some(binding) = node.cast::<ast::LetBinding>() {
-            return Some(binding.span());
-        }
-        current = node.parent().cloned();
-    }
-
-    None
-}
diff --git a/crates/tinymist-lint/src/lib.rs b/crates/tinymist-lint/src/lib.rs
index d91391808..7640ac276 100644
--- a/crates/tinymist-lint/src/lib.rs
+++ b/crates/tinymist-lint/src/lib.rs
@@ -4,6 +4,11 @@ mod dead_code;
 
 pub use dead_code::DeadCodeConfig;
 
+/// Hint added to diagnostics for documented exported functions, to mark them as
+/// likely public API.
+pub const DOCUMENTED_EXPORTED_FUNCTION_HINT: &str =
+    "this function is exported and documented; it may be part of the public API";
+
 use std::sync::Arc;
 
 use tinymist_analysis::{