JS: Overhaul import resolution

javascript/ql/lib/semmle/javascript/TSConfig.qll

@@ -0,0 +1,180 @@
+/**
+ * Provides a class for working with `tsconfig.json` files.
+ */
+
+private import javascript
+
+/**
+ * A TypeScript configuration file, usually named `tsconfig.json`.
+ */
+class TSConfig extends JsonObject {
+  TSConfig() {
+    this.getJsonFile().getBaseName().matches("%tsconfig%.json") and
+    this.isTopLevel()
+  }
+
+  /** Gets the folder containing this file. */
+  Folder getFolder() { result = this.getJsonFile().getParentContainer() }
+
+  /** Gets the `compilerOptions` object. */
+  JsonObject getCompilerOptions() { result = this.getPropValue("compilerOptions") }
+
+  /** Gets the string value in the `extends` property. */
+  string getExtendsPath() { result = this.getPropStringValue("extends") }
+
+  /** Gets the file referred to by the `extends` property. */
+  File getExtendedFile() { result = Resolver::resolve(this.getFolder(), this.getExtendsPath()) }
+
+  /** Gets the `TSConfig` file referred to by the `extends` property. */
+  TSConfig getExtendedTSConfig() { result.getJsonFile() = this.getExtendedFile() }
+
+  /** Gets the string value in the `baseUrl` property. */
+  string getBaseUrlPath() { result = this.getCompilerOptions().getPropStringValue("baseUrl") }
+
+  /** Gets the folder referred to by the `baseUrl` property in this file, not taking `extends` into account. */
+  Folder getOwnBaseUrlFolder() {
+    result = Resolver::resolve(this.getFolder(), this.getBaseUrlPath())
+  }
+
+  /** Gets the effective baseUrl folder for this tsconfig file. */
+  Folder getBaseUrlFolder() {
+    result = this.getOwnBaseUrlFolder()
+    or
+    not exists(this.getOwnBaseUrlFolder()) and
+    result = this.getExtendedTSConfig().getBaseUrlFolder()
+  }
+
+  /** Gets the effective baseUrl folder for this tsconfig file, or its enclosing folder if there is no baseUrl. */
+  Folder getBaseUrlFolderOrOwnFolder() {
+    result = this.getBaseUrlFolder()
+    or
+    not exists(this.getBaseUrlFolder()) and
+    result = this.getFolder()
+  }
+
+  /** Gets a path mentioned in the `include` property. */
+  string getAnIncludePath() {
+    result = this.getPropStringValue("include")
+    or
+    result = this.getPropValue("include").(JsonArray).getElementStringValue(_)
+  }
+
+  /**
+   * Gets a file or folder refenced by a path the `include` property, possibly
+   * inherited from an extended tsconfig file.
+   *
+   * Does not include all the files within includes directories, use `getAnIncludedContainer` for that.
+   */
+  Container getAnIncludePathTarget() {
+    result = Resolver::resolve(this.getFolder(), this.getAnIncludePath())
+    or
+    not exists(this.getPropValue("include")) and
+    result = this.getExtendedTSConfig().getAnIncludePathTarget()
+  }
+
+  /**
+   * Gets a file or folder inside the directory tree mentioned in the `include` property.
+   */
+  Container getAnIncludedContainer() {
+    result = this.getAnIncludePathTarget()
+    or
+    result = this.getAnIncludedContainer().getAChildContainer()
+  }
+
+  /** Gets the path mentioned in the `rootDir` property. */
+  string getRootDirPath() { result = this.getCompilerOptions().getPropStringValue("rootDir") }
+
+  private Container getOwnRootDir() {
+    result = Resolver::resolve(this.getFolder(), this.getRootDirPath())
+  }
+
+  /** Gets the file or folder referenced by the `rootDir` property. */
+  Container getRootDir() {
+    result = this.getOwnRootDir()
+    or
+    not exists(this.getRootDirPath()) and
+    result = this.getExtendedTSConfig().getOwnRootDir()
+  }
+
+  private string getATopLevelIncludePath() {
+    result = this.getAnIncludePath().(FilePath).getComponent(0)
+  }
+
+  private string getUniqueTopLevelIncludePath() {
+    result = unique( | | this.getATopLevelIncludePath())
+  }
+
+  /**
+   * Gets the folder referred to by the `rootDir` property, or if absent, an effective root dir
+   * derived from `include` paths.
+   */
+  Container getEffectiveRootDir() {
+    result = this.getRootDir()
+    or
+    not exists(this.getRootDir()) and
+    (
+      result = this.getFolder().getFolder(this.getUniqueTopLevelIncludePath())
+      or
+      not exists(this.getUniqueTopLevelIncludePath()) and
+      exists(this.getATopLevelIncludePath()) and
+      result = this.getFolder()
+      or
+      not exists(this.getATopLevelIncludePath()) and
+      result = this.getExtendedTSConfig().getEffectiveRootDir()
+    )
+  }
+
+  private JsonObject getPathMappings() { result = this.getCompilerOptions().getPropValue("paths") }
+
+  /**
+   * Holds if this has a path mapping from `pattern` to `newPath`.
+   *
+   * For example, `"paths": { "@/*": "./src/*" }` maps the `@/*` pattern to `./src/*`.
+   *
+   * Does not include path mappings from extended tsconfig files.
+   */
+  predicate hasPathMapping(string pattern, string newPath) {
+    this.getPathMappings().getPropStringValue(pattern) = newPath
+    or
+    this.getPathMappings().getPropValue(pattern).(JsonArray).getElementStringValue(_) = newPath
+  }
+
+  /**
+   * Holds if this has an exact path mapping from `pattern` to `newPath`.
+   *
+   * For example, `"paths": { "@": "./src/index.ts" }` maps the `@` path to `./src/index.ts`.
+   *
+   * Does not include path mappings from extended tsconfig files.
+   */
+  predicate hasExactPathMapping(string pattern, string newPath) {
+    this.hasPathMapping(pattern, newPath) and
+    not pattern.matches("%*%")
+  }
+
+  /**
+   * Holds if this has a path mapping from the `pattern` prefix to the `newPath` prefix.
+   * The trailing `*` is not included.
+   *
+   * For example, `"paths": { "@/*": "./src/*" }` maps the `@/` pattern to `./src/`.
+   *
+   * Does not include path mappings from extended tsconfig files.
+   */
+  predicate hasPrefixPathMapping(string pattern, string newPath) {
+    this.hasPathMapping(pattern + "*", newPath + "*")
+  }
+}
+
+/** For resolving paths in a tsconfig file, except `paths` mappings. */
+private module ResolverConfig implements Folder::ResolveSig {
+  predicate shouldResolve(Container base, string path) {
+    exists(TSConfig cfg |
+      base = cfg.getFolder() and
+      path =
+        [cfg.getExtendsPath(), cfg.getBaseUrlPath(), cfg.getRootDirPath(), cfg.getAnIncludePath()]
+    )
+  }
+
+  predicate allowGlobs() { any() } // "include" can use globs
+}
+
+private module Resolver = Folder::Resolve<ResolverConfig>;