Merge pull request #10036 from asgerf/js/exports-handling

JS: More precise handling of "exports"

javascript/ql/lib/semmle/javascript/NPM.qll

@@ -50,8 +50,23 @@ class PackageJson extends JsonObject {
   /** Gets a file for this package. */
   string getAFile() { result = this.getFiles().getElementStringValue(_) }
 
-  /** Gets the main module of this package. */
-  string getMain() { result = MainModulePath::of(this).getValue() }
+  /**
+   * Gets the main module of this package.
+   *
+   * This can be given by the `main` or `module` property, or via the
+   * `exports` property with the relative path `"."`.
+   */
+  string getMain() { result = this.getExportedPath(".") }
+
+  /**
+   * Gets the path to the file exported with the given relative path.
+   *
+   * This can be given by the `exports` property, but also considers `main` and
+   * `module` paths to be exported under the relative path `"."`.
+   */
+  string getExportedPath(string relativePath) {
+    result = MainModulePath::of(this, relativePath).getValue()
+  }
 
   /** Gets the path of a command defined for this package. */
   string getBin(string cmd) {
@@ -181,6 +196,18 @@ class PackageJson extends JsonObject {
     result = min(Module m, int prio | m.getFile() = resolveMainModule(this, prio) | m order by prio)
   }
 
+  /**
+   * Gets the module exported under the given relative path.
+   *
+   * The main module is considered exported under the path `"."`.
+   */
+  Module getExportedModule(string relativePath) {
+    relativePath = "." and
+    result = this.getMainModule()
+    or
+    result.getFile() = MainModulePath::of(this, relativePath).resolve()
+  }
+
   /**
    * Gets the `types` or `typings` field of this package.
    */

javascript/ql/lib/semmle/javascript/NodeModuleResolutionImpl.qll

@@ -93,7 +93,7 @@ private string getStem(string name) { result = name.regexpCapture("(.+?)(?:\\.([
  * Gets the main module described by `pkg` with the given `priority`.
  */
 File resolveMainModule(PackageJson pkg, int priority) {
-  exists(PathExpr main | main = MainModulePath::of(pkg) |
+  exists(PathExpr main | main = MainModulePath::of(pkg, ".") |
     result = main.resolve() and priority = 0
     or
     result = tryExtensions(main.resolve(), "index", priority)
@@ -142,21 +142,36 @@ File resolveMainModule(PackageJson pkg, int priority) {
 private string getASrcFolderName() { result = ["ts", "js", "src", "lib"] }
 
 /**
- * A JSON string in a `package.json` file specifying the path of the main
- * module of the package.
+ * A JSON string in a `package.json` file specifying the path of one of the exported
+ * modules of the package.
  */
 class MainModulePath extends PathExpr, @json_string {
   PackageJson pkg;
+  string relativePath;
 
   MainModulePath() {
+    relativePath = "." and
     this = pkg.getPropValue(["main", "module"])
     or
-    this = getAJsonChild*(pkg.getPropValue("exports"))
+    // { "exports": "path" } is sugar for { "exports": { ".": "path" }}
+    relativePath = "." and
+    this = pkg.getPropValue("exports")
+    or
+    exists(JsonValue val | val = pkg.getPropValue("exports").getPropValue(relativePath) |
+      // Either specified directly as a string: { "./path": "./path.js" }
+      this = val
+      or
+      // Or by module type: { "./path": { "require": "./path.cjs", ... }}
+      this = val.getPropValue(_)
+    )
   }
 
   /** Gets the `package.json` file in which this path occurs. */
   PackageJson getPackageJson() { result = pkg }
 
+  /** Gets the relative path under which this is exported, usually starting with a `.`. */
+  string getRelativePath() { result = relativePath }
+
   /** DEPRECATED: Alias for getPackageJson */
   deprecated PackageJSON getPackageJSON() { result = getPackageJson() }
 
@@ -168,11 +183,15 @@ class MainModulePath extends PathExpr, @json_string {
   }
 }
 
-/** Gets the value of a property from the JSON object `obj`. */
-private JsonValue getAJsonChild(JsonObject obj) { result = obj.getPropValue(_) }
-
 module MainModulePath {
-  MainModulePath of(PackageJson pkg) { result.getPackageJson() = pkg }
+  /** Gets the path to the main entry point of `pkg`. */
+  MainModulePath of(PackageJson pkg) { result = of(pkg, ".") }
+
+  /** Gets the path to the file exported from `pkg` as `relativePath`. */
+  MainModulePath of(PackageJson pkg, string relativePath) {
+    result.getPackageJson() = pkg and
+    result.getRelativePath() = relativePath
+  }
 }
 
 /**
@@ -185,7 +204,7 @@ private class FilesPath extends PathExpr, @json_string {
 
   FilesPath() {
     this = pkg.getPropValue("files").(JsonArray).getElementValue(_) and
-    not exists(MainModulePath::of(pkg))
+    not exists(MainModulePath::of(pkg, _))
   }
 
   /** Gets the `package.json` file in which this path occurs. */

javascript/ql/lib/semmle/javascript/PackageExports.qll

@@ -52,7 +52,7 @@ private import NodeModuleResolutionImpl as NodeModule
 private DataFlow::Node getAValueExportedByPackage() {
   // The base case, an export from a named `package.json` file.
   result =
-    getAnExportFromModule(any(PackageJson pack | exists(pack.getPackageName())).getMainModule())
+    getAnExportFromModule(any(PackageJson pack | exists(pack.getPackageName())).getExportedModule(_))
   or
   // module.exports.bar.baz = result;
   exists(DataFlow::PropWrite write |