Implement basic Documentation source to syntax range mapping

5 files changed, 149 insertions, 36 deletions

diff --git a/crates/hir_def/src/attr.rs b/crates/hir_def/src/attr.rs
index 52a2bce9b..7791402c9 100644
--- a/crates/hir_def/src/attr.rs
+++ b/crates/hir_def/src/attr.rs
@@ -1,6 +1,10 @@
 //! A higher level attributes based on TokenTree, with also some shortcuts.
 
-use std::{ops, sync::Arc};
+use std::{
+    cmp::Ordering,
+    ops::{self, Range},
+    sync::Arc,
+};
 
 use base_db::CrateId;
 use cfg::{CfgExpr, CfgOptions};
@@ -12,7 +16,7 @@ use mbe::ast_to_token_tree;
 use smallvec::{smallvec, SmallVec};
 use syntax::{
     ast::{self, AstNode, AttrsOwner},
-    match_ast, AstToken, SmolStr, SyntaxNode,
+    match_ast, AstToken, SmolStr, SyntaxNode, TextRange, TextSize,
 };
 use tt::Subtree;
 
@@ -451,6 +455,54 @@ impl AttrsWithOwner {
                 .collect(),
         }
     }
+
+    pub fn docs_with_rangemap(
+        &self,
+        db: &dyn DefDatabase,
+    ) -> Option<(Documentation, DocsRangeMap)> {
+        // FIXME: code duplication in `docs` above
+        let docs = self.by_key("doc").attrs().flat_map(|attr| match attr.input.as_ref()? {
+            AttrInput::Literal(s) => Some((s, attr.index)),
+            AttrInput::TokenTree(_) => None,
+        });
+        let indent = docs
+            .clone()
+            .flat_map(|(s, _)| s.lines())
+            .filter(|line| !line.chars().all(|c| c.is_whitespace()))
+            .map(|line| line.chars().take_while(|c| c.is_whitespace()).count())
+            .min()
+            .unwrap_or(0);
+        let mut buf = String::new();
+        let mut mapping = Vec::new();
+        for (doc, idx) in docs {
+            // str::lines doesn't yield anything for the empty string
+            if !doc.is_empty() {
+                for line in doc.split('\n') {
+                    let line = line.trim_end();
+                    let (offset, line) = match line.char_indices().nth(indent) {
+                        Some((offset, _)) => (offset, &line[offset..]),
+                        None => (0, line),
+                    };
+                    let buf_offset = buf.len();
+                    buf.push_str(line);
+                    mapping.push((
+                        Range { start: buf_offset, end: buf.len() },
+                        idx,
+                        Range { start: offset, end: line.len() },
+                    ));
+                    buf.push('\n');
+                }
+            } else {
+                buf.push('\n');
+            }
+        }
+        buf.pop();
+        if buf.is_empty() {
+            None
+        } else {
+            Some((Documentation(buf), DocsRangeMap { mapping, source: self.source_map(db).attrs }))
+        }
+    }
 }
 
 fn inner_attributes(
@@ -507,6 +559,59 @@ impl AttrSourceMap {
     }
 }
 
+/// A struct to map text ranges from [`Documentation`] back to TextRanges in the syntax tree.
+pub struct DocsRangeMap {
+    source: Vec<InFile<Either<ast::Attr, ast::Comment>>>,
+    // (docstring-line-range, attr_index, attr-string-range)
+    // a mapping from the text range of a line of the [`Documentation`] to the attribute index and
+    // the original (untrimmed) syntax doc line
+    mapping: Vec<(Range<usize>, u32, Range<usize>)>,
+}
+
+impl DocsRangeMap {
+    pub fn map(&self, range: Range<usize>) -> Option<InFile<TextRange>> {
+        let found = self
+            .mapping
+            .binary_search_by(|(probe, ..)| {
+                if probe.contains(&range.start) {
+                    Ordering::Equal
+                } else {
+                    probe.start.cmp(&range.end)
+                }
+            })
+            .ok()?;
+        let (line_docs_range, idx, original_line_src_range) = self.mapping[found].clone();
+        if range.end > line_docs_range.end {
+            return None;
+        }
+
+        let relative_range = Range {
+            start: range.start - line_docs_range.start,
+            end: range.end - line_docs_range.start,
+        };
+        let range_len = TextSize::from((range.end - range.start) as u32);
+
+        let &InFile { file_id, value: ref source } = &self.source[idx as usize];
+        match source {
+            Either::Left(_) => None, // FIXME, figure out a nice way to handle doc attributes here
+            // as well as for whats done in syntax highlight doc injection
+            Either::Right(comment) => {
+                let text_range = comment.syntax().text_range();
+                let range = TextRange::at(
+                    text_range.start()
+                        + TextSize::from(
+                            (comment.prefix().len()
+                                + original_line_src_range.start
+                                + relative_range.start) as u32,
+                        ),
+                    text_range.len().min(range_len),
+                );
+                Some(InFile { file_id, value: range })
+            }
+        }
+    }
+}
+
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub struct Attr {
     index: u32,
diff --git a/crates/ide/src/goto_definition.rs b/crates/ide/src/goto_definition.rs
index 4e4d1b200..1951c599f 100644
--- a/crates/ide/src/goto_definition.rs
+++ b/crates/ide/src/goto_definition.rs
@@ -32,6 +32,7 @@ pub(crate) fn goto_definition(
     let parent = token.parent()?;
     if let Some(comment) = ast::Comment::cast(token) {
         let docs = doc_owner_to_def(&sema, &parent)?.docs(db)?;
+
         let (_, link, ns) = extract_positioned_link_from_comment(position.offset, &comment, docs)?;
         let def = doc_owner_to_def(&sema, &parent)?;
         let nav = resolve_doc_path_for_def(db, def, &link, ns)?.try_to_nav(db)?;
diff --git a/crates/ide/src/syntax_highlighting/inject.rs b/crates/ide/src/syntax_highlighting/inject.rs
index b62d43256..504783f31 100644
--- a/crates/ide/src/syntax_highlighting/inject.rs
+++ b/crates/ide/src/syntax_highlighting/inject.rs
@@ -1,6 +1,6 @@
 //! "Recursive" Syntax highlighting for code in doctests and fixtures.
 
-use std::{mem, ops::Range};
+use std::mem;
 
 use either::Either;
 use hir::{HasAttrs, InFile, Semantics};
@@ -139,8 +139,28 @@ pub(super) fn doc_comment(
     // Replace the original, line-spanning comment ranges by new, only comment-prefix
     // spanning comment ranges.
     let mut new_comments = Vec::new();
-    let mut intra_doc_links = Vec::new();
     let mut string;
+
+    if let Some((docs, doc_mapping)) = attributes.docs_with_rangemap(sema.db) {
+        extract_definitions_from_markdown(docs.as_str())
+            .into_iter()
+            .filter_map(|(range, link, ns)| {
+                let def = resolve_doc_path_for_def(sema.db, def, &link, ns)?;
+                let InFile { file_id, value: range } = doc_mapping.map(range)?;
+                (file_id == node.file_id).then(|| (range, def))
+            })
+            .for_each(|(range, def)| {
+                hl.add(HlRange {
+                    range,
+                    highlight: module_def_to_hl_tag(def)
+                        | HlMod::Documentation
+                        | HlMod::Injected
+                        | HlMod::IntraDocLink,
+                    binding_hash: None,
+                })
+            });
+    }
+
     for attr in attributes.by_key("doc").attrs() {
         let InFile { file_id, value: src } = attrs_source_map.source_of(&attr);
         if file_id != node.file_id {
@@ -186,25 +206,7 @@ pub(super) fn doc_comment(
                     is_doctest = is_codeblock && is_rust;
                     continue;
                 }
-                None if !is_doctest => {
-                    intra_doc_links.extend(
-                        extract_definitions_from_markdown(line)
-                            .into_iter()
-                            .filter_map(|(range, link, ns)| {
-                                Some(range).zip(resolve_doc_path_for_def(sema.db, def, &link, ns))
-                            })
-                            .map(|(Range { start, end }, def)| {
-                                (
-                                    def,
-                                    TextRange::at(
-                                        prev_range_start + TextSize::from(start as u32),
-                                        TextSize::from((end - start) as u32),
-                                    ),
-                                )
-                            }),
-                    );
-                    continue;
-                }
+                None if !is_doctest => continue,
                 None => (),
             }
 
@@ -223,17 +225,6 @@ pub(super) fn doc_comment(
         }
     }
 
-    for (def, range) in intra_doc_links {
-        hl.add(HlRange {
-            range,
-            highlight: module_def_to_hl_tag(def)
-                | HlMod::Documentation
-                | HlMod::Injected
-                | HlMod::IntraDocLink,
-            binding_hash: None,
-        });
-    }
-
     if new_comments.is_empty() {
         return; // no need to run an analysis on an empty file
     }
diff --git a/crates/ide/src/syntax_highlighting/test_data/highlight_doctest.html b/crates/ide/src/syntax_highlighting/test_data/highlight_doctest.html
index 045162eb8..b6d1cac4e 100644
--- a/crates/ide/src/syntax_highlighting/test_data/highlight_doctest.html
+++ b/crates/ide/src/syntax_highlighting/test_data/highlight_doctest.html
@@ -100,10 +100,18 @@ pre                 { color: #DCDCCC; background: #3F3F3F; font-size: 22px; padd
 <span class="brace">}</span>
 
 <span class="comment documentation">/// </span><span class="struct documentation intra_doc_link injected">[`Foo`](Foo)</span><span class="comment documentation"> is a struct</span>
-<span class="comment documentation">/// </span><span class="function documentation intra_doc_link injected">[`all_the_links`](all_the_links)</span><span class="comment documentation"> is this function</span>
+<span class="comment documentation">/// This function is &gt; </span><span class="function documentation intra_doc_link injected">[`all_the_links`](all_the_links)</span><span class="comment documentation"> &lt;</span>
 <span class="comment documentation">/// [`noop`](noop) is a macro below</span>
+<span class="comment documentation">/// </span><span class="struct documentation intra_doc_link injected">[`Item`]</span><span class="comment documentation"> is a struct in the module </span><span class="module documentation intra_doc_link injected">[`module`]</span>
+<span class="comment documentation">///</span>
+<span class="comment documentation">/// [`Item`]: module::Item</span>
+<span class="comment documentation">/// [mix_and_match]: ThisShouldntResolve</span>
 <span class="keyword">pub</span> <span class="keyword">fn</span> <span class="function declaration">all_the_links</span><span class="parenthesis">(</span><span class="parenthesis">)</span> <span class="brace">{</span><span class="brace">}</span>
 
+<span class="keyword">pub</span> <span class="keyword">mod</span> <span class="module declaration">module</span> <span class="brace">{</span>
+    <span class="keyword">pub</span> <span class="keyword">struct</span> <span class="struct declaration">Item</span><span class="semicolon">;</span>
+<span class="brace">}</span>
+
 <span class="comment documentation">/// ```</span>
 <span class="comment documentation">/// </span><span class="macro injected">noop!</span><span class="parenthesis injected">(</span><span class="numeric_literal injected">1</span><span class="parenthesis injected">)</span><span class="semicolon injected">;</span>
 <span class="comment documentation">/// ```</span>
diff --git a/crates/ide/src/syntax_highlighting/tests.rs b/crates/ide/src/syntax_highlighting/tests.rs
index 369ae0972..1b02857ec 100644
--- a/crates/ide/src/syntax_highlighting/tests.rs
+++ b/crates/ide/src/syntax_highlighting/tests.rs
@@ -544,10 +544,18 @@ impl Foo {
 }
 
 /// [`Foo`](Foo) is a struct
-/// [`all_the_links`](all_the_links) is this function
+/// This function is > [`all_the_links`](all_the_links) <
 /// [`noop`](noop) is a macro below
+/// [`Item`] is a struct in the module [`module`]
+///
+/// [`Item`]: module::Item
+/// [mix_and_match]: ThisShouldntResolve
 pub fn all_the_links() {}
 
+pub mod module {
+    pub struct Item;
+}
+
 /// ```
 /// noop!(1);
 /// ```