Rust: Handle path attributes in path resolution

rust/ql/lib/codeql/files/FileSystem.qll

@@ -34,6 +34,8 @@ class Container = Impl::Container;
 
 class Folder = Impl::Folder;
 
+module Folder = Impl::Folder;
+
 /** A file. */
 class File extends Container, Impl::File {
   /** Holds if this file was extracted from ordinary source code. */

rust/ql/lib/codeql/rust/internal/PathResolution.qll

@@ -655,6 +655,11 @@ private predicate fileModule(SourceFile f, string name, Folder folder) {
   )
 }
 
+private Meta getPathAttrMeta(Module m) {
+  result = m.getAnAttr().getMeta() and
+  result.getPath().getText() = "path"
+}
+
 /**
  * Holds if `m` is a `mod name;` module declaration, where the corresponding
  * module file needs to be looked up in `lookup` or one of its descandants.
@@ -663,12 +668,7 @@ private predicate modImport0(Module m, string name, Folder lookup) {
   exists(File f, Folder parent, string fileName |
     f = m.getFile() and
     not m.hasItemList() and
-    // TODO: handle
-    // ```
-    // #[path = "foo.rs"]
-    // mod bar;
-    // ```
-    not m.getAnAttr().getMeta().getPath().getText() = "path" and
+    not exists(getPathAttrMeta(m)) and
     name = m.getName().getText() and
     parent = f.getParentContainer() and
     fileName = f.getStem()
@@ -717,6 +717,16 @@ private predicate modImportNestedLookup(Module m, ModuleItemNode ancestor, Folde
   )
 }
 
+private predicate pathAttrImport(Folder f, Module m, string relativePath) {
+  exists(Meta meta |
+    f = m.getFile().getParentContainer() and
+    meta = getPathAttrMeta(m) and
+    relativePath = meta.getExpr().(LiteralExpr).getTextValue().regexpCapture("\"(.+)\"", 1)
+  )
+}
+
+private predicate append(Folder f, string relativePath) { pathAttrImport(f, _, relativePath) }
+
 /** Holds if `m` is a `mod name;` item importing file `f`. */
 private predicate fileImport(Module m, SourceFile f) {
   exists(string name, Folder parent |
@@ -730,6 +740,11 @@ private predicate fileImport(Module m, SourceFile f) {
     // `m` is inside a nested module
     modImportNestedLookup(m, m, parent)
   )
+  or
+  exists(Folder folder, string relativePath |
+    pathAttrImport(folder, m, relativePath) and
+    f.getFile() = Folder::Append<append/2>::append(folder, relativePath)
+  )
 }
 
 /**

rust/ql/test/library-tests/path-resolution/my2/mod.rs

@@ -14,4 +14,4 @@ pub mod my3;
 #[path = "renamed.rs"]
 mod mymod;
 
-use mymod::f; // $ MISSING: item=I1001
+use mymod::f; // $ item=I1001

rust/ql/test/library-tests/path-resolution/path-resolution.expected

@@ -308,12 +308,13 @@ resolvePath
 | my2/mod.rs:10:9:10:33 | ...::nested8 | my2/nested2.rs:22:5:26:5 | mod nested8 |
 | my2/mod.rs:10:37:10:40 | self | my2/nested2.rs:22:5:26:5 | mod nested8 |
 | my2/mod.rs:17:5:17:9 | mymod | my2/mod.rs:14:1:15:10 | mod mymod |
+| my2/mod.rs:17:5:17:12 | ...::f | my2/renamed.rs:1:1:1:13 | fn f |
 | my2/my3/mod.rs:3:5:3:5 | g | my2/mod.rs:3:1:6:1 | fn g |
 | my2/my3/mod.rs:4:5:4:5 | h | main.rs:50:1:69:1 | fn h |
-| my2/my3/mod.rs:7:5:7:9 | super | my2/mod.rs:1:1:17:39 | SourceFile |
+| my2/my3/mod.rs:7:5:7:9 | super | my2/mod.rs:1:1:17:30 | SourceFile |
 | my2/my3/mod.rs:7:5:7:16 | ...::super | main.rs:1:1:578:2 | SourceFile |
 | my2/my3/mod.rs:7:5:7:19 | ...::h | main.rs:50:1:69:1 | fn h |
-| my2/my3/mod.rs:8:5:8:9 | super | my2/mod.rs:1:1:17:39 | SourceFile |
+| my2/my3/mod.rs:8:5:8:9 | super | my2/mod.rs:1:1:17:30 | SourceFile |
 | my2/my3/mod.rs:8:5:8:12 | ...::g | my2/mod.rs:3:1:6:1 | fn g |
 | my.rs:3:5:3:10 | nested | my.rs:1:1:1:15 | mod nested |
 | my.rs:3:5:3:13 | ...::g | my/nested.rs:19:1:22:1 | fn g |

shared/util/codeql/util/FileSystem.qll

@@ -218,6 +218,53 @@ module Make<InputSig Input> {
     /** Gets the URL of this file. */
     override string getURL() { result = "file://" + this.getAbsolutePath() + ":0:0:0:0" }
   }
+
+  /** Provides logic related to `Folder`s. */
+  module Folder {
+    /** Holds if `relativePath` needs to be appended to `f`. */
+    signature predicate appendSig(Folder f, string relativePath);
+
+    /** Provides the `append` predicate for appending a relative path onto a folder. */
+    module Append<appendSig/2 app> {
+      pragma[nomagic]
+      private string getComponent(string relativePath, int i) {
+        app(_, relativePath) and
+        result = relativePath.replaceAll("\\", "/").regexpFind("[^/]+", i, _)
+      }
+
+      pragma[nomagic]
+      private Container appendStep(Folder f, string relativePath, int i) {
+        i = -1 and
+        app(f, relativePath) and
+        result = f
+        or
+        exists(Container mid, string comp |
+          mid = appendStep(f, relativePath, i - 1) and
+          comp = getComponent(relativePath, i) and
+          if comp = ".."
+          then result = mid.getParentContainer()
+          else
+            if comp = "."
+            then result = mid
+            else (
+              result = mid.getAChildContainer() and
+              result.getBaseName() = comp
+            )
+        )
+      }
+
+      /**
+       * Gets the file or folder obtained by appending `relativePath` onto `f`.
+       */
+      pragma[nomagic]
+      Container append(Folder f, string relativePath) {
+        exists(int components |
+          components = (-1).maximum(max(int comp | exists(getComponent(relativePath, comp)) | comp)) and
+          result = appendStep(f, relativePath, components)
+        )
+      }
+    }
+  }
 }
 
 /** A file. */