JS: Add support for Promise.try

Author: asgerf

javascript/ql/lib/semmle/javascript/internal/flow_summaries/FlowSummaryUtil.qll

@@ -49,3 +49,10 @@ string getAnArrayContent() {
   // Values stored at an unknown index
   result = "ArrayElement[?]"
 }
+
+/**
+ * Gets an argument position up to a certain limit.
+ *
+ * This can be used to generate flow summaries that should preserve such positions.
+ */
+int getAnArgumentPosition() { result = [0 .. 10] }

javascript/ql/lib/semmle/javascript/internal/flow_summaries/Promises.qll

@@ -368,3 +368,29 @@ private class PromiseWithResolversLike extends SummarizedCallable {
     )
   }
 }
+
+class PromiseTry extends DataFlow::SummarizedCallable {
+  PromiseTry() { this = "Promise.try()" }
+
+  override DataFlow::CallNode getACallSimple() {
+    result = promiseConstructorRef().getAMemberCall(["try", "attempt"])
+    or
+    result = DataFlow::moduleImport(["p-try", "es6-promise-try"]).getACall()
+  }
+
+  override predicate propagatesFlow(string input, string output, boolean preservesValue) {
+    preservesValue = true and
+    (
+      exists(int i | i = getAnArgumentPosition() |
+        input = "Argument[" + (i + 1) + "]" and
+        output = "Argument[0].Parameter[" + i + "]"
+      )
+      or
+      input = "Argument[0].ReturnValue" and
+      output = "ReturnValue.Awaited"
+      or
+      input = "Argument[0].ReturnValue[exception]" and
+      output = "ReturnValue.Awaited[error]"
+    )
+  }
+}

javascript/ql/test/library-tests/TripleDot/promise-try.js

@@ -0,0 +1,29 @@
+async function t1() {
+    const promise = Promise.try(() => {
+        return source('try.1');
+    });
+    sink(await promise); // $ hasValueFlow=try.1
+}
+
+async function t2() {
+    const promise = Promise.try((x) => {
+        return x
+    }, source('try.2'));
+    sink(await promise); // $ hasValueFlow=try.2
+}
+
+async function t3() {
+    const promise = Promise.try((x) => {
+        throw x;
+    }, source('try.3'));
+    promise.catch(err => {
+        sink(err); // $ hasValueFlow=try.3
+    });
+}
+
+async function t4() {
+    const promise = Promise.try((x, y) => {
+        return y;
+    }, source('try.4.1'), source('try.4.2'));
+    sink(await promise); //  $ hasValueFlow=try.4.2
+}