ziglang · achan1989 · Apr 13, 2025
diff --git a/lib/docs/main.js b/lib/docs/main.js
@@ -56,6 +56,9 @@
     const domErrors = document.getElementById("errors");
     const domErrorsText = document.getElementById("errorsText");
 
+    // Chosen to prevent collisions with the IDs above.
+    const navPrefix = "nav_";
+
     var searchTimer = null;
 
     const curNav = {
@@ -67,6 +70,8 @@
       decl: null,
       // string file name matching tarball path
       path: null,
+      // string decl path within source file
+      scrollToDeclPath: null,
 
       // when this is populated, pressing the "view source" command will
       // navigate to this hash.
@@ -180,7 +185,7 @@
             } else {
               return renderDecl(curNav.decl);
             }
-          case 2: return renderSource(curNav.path);
+          case 2: return renderSource(curNav.path, curNav.scrollToDeclPath);
           default: throw new Error("invalid navigation state");
         }
     }
@@ -224,22 +229,44 @@
       }
     }
 
-    function renderSource(path) {
-      const decl_index = findFileRoot(path);
-      if (decl_index == null) return renderNotFound();
+    function renderSource(path, scroll_to_decl_path) {
+      const root_index = findFileRoot(path);
+      if (root_index == null) return renderNotFound();
 
-      renderNavFancy(decl_index, [{
+      renderNavFancy(root_index, [{
         name: "[src]",
         href: location.hash,
       }]);
 
-      domSourceText.innerHTML = declSourceHtml(decl_index);
-
+      domSourceText.innerHTML = declSourceHtml(root_index, true);
       domSectSource.classList.remove("hidden");
+
+      const scroll_to_decl_index = findDeclPathInNamespace(root_index, scroll_to_decl_path);
+      if (scroll_to_decl_index !== null) {
+        const to_elem = document.getElementById(navPrefix + scroll_to_decl_index);
+        if (to_elem != null) {
+          setTimeout(function() {
+            to_elem.scrollIntoView();
+          }, 0);
+        }
+      }
     }
 
     function renderDeclHeading(decl_index) {
       curNav.viewSourceHash = "#src/" + unwrapString(wasm_exports.decl_file_path(decl_index));
+      const is_root = wasm_exports.decl_is_root(decl_index);
+      if (!is_root) {
+        // E.g. if `decl_index` corresponds to `root.foo.bar` we want `foo.bar`
+        var subcomponents = [];
+        let decl_it = decl_index;
+        while (decl_it != null) {
+          subcomponents.push(declIndexName(decl_it));
+          decl_it = declParent(decl_it);
+        }
+        subcomponents.pop();
+        subcomponents.reverse();
+        curNav.viewSourceHash += ":" + subcomponents.join(".");
+      }
 
       const hdrNameSpan = domHdrName.children[0];
       const srcLink = domHdrName.children[1];
@@ -384,7 +411,7 @@
       if (members.length !== 0 || fields.length !== 0) {
         renderNamespace(decl_index, members, fields);
       } else {
-        domSourceText.innerHTML = declSourceHtml(decl_index);
+        domSourceText.innerHTML = declSourceHtml(decl_index, false);
         domSectSource.classList.remove("hidden");
       }
     }
@@ -414,7 +441,7 @@
         renderErrorSet(base_decl, errorSetNodeList(decl_index, errorSetNode));
       }
 
-      domSourceText.innerHTML = declSourceHtml(decl_index);
+      domSourceText.innerHTML = declSourceHtml(decl_index, false);
       domSectSource.classList.remove("hidden");
     }
 
@@ -428,7 +455,7 @@
         domTldDocs.classList.remove("hidden");
       }
 
-      domSourceText.innerHTML = declSourceHtml(decl_index);
+      domSourceText.innerHTML = declSourceHtml(decl_index, false);
       domSectSource.classList.remove("hidden");
     }
 
@@ -615,6 +642,7 @@
         curNav.tag = 0;
         curNav.decl = null;
         curNav.path = null;
+        curNav.scrollToDeclPath = null;
         curNav.viewSourceHash = null;
         curNavSearch = "";
 
@@ -633,7 +661,13 @@
               const source_mode = nonSearchPart.startsWith("src/");
               if (source_mode) {
                 curNav.tag = 2;
-                curNav.path = nonSearchPart.substring(4);
+                const idpos = nonSearchPart.indexOf(":");
+                if (idpos === -1) {
+                  curNav.path = nonSearchPart.substring(4);
+                } else {
+                  curNav.path = nonSearchPart.substring(4, idpos);
+                  curNav.scrollToDeclPath = nonSearchPart.substring(idpos + 1);
+                }
               } else {
                 curNav.tag = 1;
                 curNav.decl = findDecl(nonSearchPart);
@@ -904,8 +938,8 @@
       return unwrapString(wasm_exports.decl_name(decl_index));
     }
 
-    function declSourceHtml(decl_index) {
-      return unwrapString(wasm_exports.decl_source_html(decl_index));
+    function declSourceHtml(decl_index, decl_nav_targets) {
+      return unwrapString(wasm_exports.decl_source_html(decl_index, decl_nav_targets));
     }
 
     function declDoctestHtml(decl_index) {
@@ -973,6 +1007,13 @@
       return result;
     }
 
+    function findDeclPathInNamespace(namespace_decl_index, path) {
+      setInputString(path);
+      const result = wasm_exports.find_decl_path_in_namespace(namespace_decl_index);
+      if (result === -1) return null;
+      return result;
+    }
+
     function findFileRoot(path) {
       setInputString(path);
       const result = wasm_exports.find_file_root();

diff --git a/lib/docs/wasm/Walk.zig b/lib/docs/wasm/Walk.zig
@@ -53,6 +53,27 @@ pub const File = struct {
     /// struct/union/enum/opaque decl node => its namespace scope
     /// local var decl node => its local variable scope
     scopes: std.AutoArrayHashMapUnmanaged(Ast.Node.Index, *Scope) = .empty,
+    /// Last decl in the file (exclusive).
+    decl_end: Decl.Index = .none,
+
+    pub const DeclIter = struct {
+        idx: DeclIndexTagType,
+        end: DeclIndexTagType,
+
+        const DeclIndexTagType = @typeInfo(Decl.Index).@"enum".tag_type;
+
+        pub fn next(iter: *DeclIter) ?Decl.Index {
+            if (iter.idx >= iter.end) return null;
+            const decl_idx = iter.idx;
+            iter.idx += 1;
+            return @enumFromInt(decl_idx);
+        }
+
+        pub fn remaining(iter: DeclIter) usize {
+            if (iter.idx >= iter.end) return 0;
+            return iter.end - iter.idx;
+        }
+    };
 
     pub fn lookup_token(file: *File, token: Ast.TokenIndex) Decl.Index {
         const decl_node = file.ident_decls.get(token) orelse return .none;
@@ -89,6 +110,18 @@ pub const File = struct {
             return file_index.get().node_decls.values()[0];
         }
 
+        /// Excludes the root decl.
+        /// Only valid after `Walk.add_file()`.
+        pub fn iterDecls(file_index: File.Index) DeclIter {
+            const root_idx = @intFromEnum(file_index.findRootDecl());
+            const end_idx = file_index.get().decl_end;
+            assert(end_idx != .none);
+            return DeclIter{
+                .idx = root_idx + 1,
+                .end = @intFromEnum(end_idx),
+            };
+        }
+
         pub fn categorize_decl(file_index: File.Index, node: Ast.Node.Index) Category {
             const ast = file_index.get_ast();
             switch (ast.nodeTag(node)) {
@@ -405,6 +438,7 @@ pub fn add_file(file_name: []const u8, bytes: []u8) !File.Index {
     try struct_decl(&w, scope, decl_index, .root, ast.containerDeclRoot());
 
     const file = file_index.get();
+    file.decl_end = @enumFromInt(decls.items.len);
     shrinkToFit(&file.ident_decls);
     shrinkToFit(&file.token_parents);
     shrinkToFit(&file.node_decls);

diff --git a/lib/docs/wasm/html_render.zig b/lib/docs/wasm/html_render.zig
@@ -11,10 +11,15 @@ const Oom = error{OutOfMemory};
 /// Delete this to find out where URL escaping needs to be added.
 pub const missing_feature_url_escape = true;
 
+/// Prevents collisions with IDs in index.html
+/// Keep in sync with the `navPrefix` constant in `main.js`.
+pub const nav_prefix: []const u8 = "nav_";
+
 pub const RenderSourceOptions = struct {
     skip_doc_comments: bool = false,
     skip_comments: bool = false,
     collapse_whitespace: bool = false,
+    /// Render a specific function as a link to its documentation.
     fn_link: Decl.Index = .none,
     /// Assumed to be sorted ascending.
     source_location_annotations: []const Annotation = &.{},

diff --git a/lib/docs/wasm/main.zig b/lib/docs/wasm/main.zig
@@ -6,7 +6,8 @@ const Walk = @import("Walk");
 const markdown = @import("markdown.zig");
 const Decl = Walk.Decl;
 
-const fileSourceHtml = @import("html_render.zig").fileSourceHtml;
+const html_render = @import("html_render.zig");
+const fileSourceHtml = html_render.fileSourceHtml;
 const appendEscaped = @import("html_render.zig").appendEscaped;
 const resolveDeclLink = @import("html_render.zig").resolveDeclLink;
 const missing_feature_url_escape = @import("html_render.zig").missing_feature_url_escape;
@@ -541,11 +542,38 @@ export fn decl_fn_proto_html(decl_index: Decl.Index, linkify_fn_name: bool) Stri
     return String.init(string_result.items);
 }
 
-export fn decl_source_html(decl_index: Decl.Index) String {
+/// `decl_nav_targets`: create targets for jumping to decls. If true, asserts `decl_index` is the
+/// root decl of a file.
+export fn decl_source_html(decl_index: Decl.Index, decl_nav_targets: bool) String {
     const decl = decl_index.get();
 
+    var sla: std.ArrayListUnmanaged(html_render.Annotation) = .empty;
+    defer sla.deinit(gpa);
+    if (decl_nav_targets) {
+        const root_file = decl_index.get().file;
+        assert(decl_index == root_file.findRootDecl());
+
+        const ast = root_file.get_ast();
+        var it = root_file.iterDecls();
+        sla.ensureTotalCapacityPrecise(gpa, it.remaining()) catch @panic("OOM");
+        while (true) {
+            const inner_decl_index = (it.next() orelse break);
+            const inner_decl = inner_decl_index.get();
+            if (!inner_decl.is_pub()) continue;
+            const decl_tok = ast.firstToken(inner_decl.ast_node);
+            const tok_start = ast.tokenStart(decl_tok);
+            sla.appendAssumeCapacity(.{
+                .file_byte_offset = tok_start,
+                .dom_id = @intFromEnum(inner_decl_index),
+            });
+        }
+    }
+
     string_result.clearRetainingCapacity();
-    fileSourceHtml(decl.file, &string_result, decl.ast_node, .{}) catch |err| {
+    fileSourceHtml(decl.file, &string_result, decl.ast_node, .{
+        .source_location_annotations = sla.items,
+        .annotation_prefix = html_render.nav_prefix,
+    }) catch |err| {
         std.debug.panic("unable to render source: {s}", .{@errorName(err)});
     };
     return String.init(string_result.items);
@@ -841,6 +869,11 @@ export fn find_file_root() Decl.Index {
     return file.findRootDecl();
 }
 
+/// Does the decl correspond to the root struct of a file?
+export fn decl_is_root(decl_index: Decl.Index) bool {
+    return decl_index.get().file.findRootDecl() == decl_index;
+}
+
 /// Uses `input_string`.
 /// Tries to look up the Decl component-wise but then falls back to a file path
 /// based scan.
@@ -863,6 +896,13 @@ export fn find_decl() Decl.Index {
     return .none;
 }
 
+/// Uses `input_string` as a decl path.
+/// Start in the namespace corresponding to `decl_index`, find a child decl by path.
+/// The path can contain multiple components e.g. `foo.bar`.
+export fn find_decl_path_in_namespace(decl_index: Decl.Index) Decl.Index {
+    return resolve_decl_path(decl_index, input_string.items) orelse .none;
+}
+
 /// Set only by `categorize_decl`; read only by `get_aliasee`, valid only
 /// when `categorize_decl` returns `.alias`.
 var global_aliasee: Decl.Index = .none;