JS: Deprecate getUnknownMember() and replace its uses with getArrayElement()

Although they mean slightly different things, every single call site
of getUnknownMember() just used it as a way to get array elements.

Since there is no known use-case for the original meaning of
getUnknownMember() I am deprecating it for now.

javascript/ql/lib/semmle/javascript/ApiGraphs.qll

@@ -10,6 +10,7 @@ private import semmle.javascript.dataflow.internal.FlowSteps as FlowSteps
 private import semmle.javascript.dataflow.internal.PreCallGraphStep
 private import semmle.javascript.dataflow.internal.StepSummary
 private import semmle.javascript.dataflow.internal.sharedlib.SummaryTypeTracker as SummaryTypeTracker
+private import semmle.javascript.dataflow.internal.Contents::Private as ContentPrivate
 private import internal.CachedStages
 
 /**
@@ -222,13 +223,17 @@ module API {
     }
 
     /**
-     * Gets a node representing a member of this API component where the name of the member is
-     * not known statically.
+     * DEPRECATED. Use either `getArrayElement()` or `getAMember()` instead.
+     */
+    deprecated Node getUnknownMember() { result = this.getArrayElement() }
+
+    /**
+     * Gets an array element of unknown index.
      */
     cached
-    Node getUnknownMember() {
+    Node getUnknownArrayElement() {
       Stages::ApiStage::ref() and
-      result = this.getASuccessor(Label::unknownMember())
+      result = this.getASuccessor(Label::content(ContentPrivate::MkArrayElementUnknown()))
     }
 
     cached
@@ -274,7 +279,7 @@ module API {
       Stages::ApiStage::ref() and
       result = this.getMember(_)
       or
-      result = this.getUnknownMember()
+      result = this.getUnknownArrayElement()
     }
 
     /**
@@ -1505,7 +1510,12 @@ module API {
     /** Gets the `content` edge label for content `c`. */
     LabelContent content(ContentPrivate::Content c) { result.getContent() = c }
 
-    /** Gets the `member` edge label for the unknown member. */
+    /**
+     * Gets the edge label for an unknown member.
+     *
+     * Currently this is represented the same way as an unknown array element, but this may
+     * change in the future.
+     */
     LabelContent unknownMember() { result.getContent().isUnknownArrayElement() }
 
     /**
@@ -1580,7 +1590,6 @@ module API {
     /** Gets an entry-point label for the entry-point `e`. */
     LabelEntryPoint entryPoint(API::EntryPoint e) { result.getEntryPoint() = e }
 
-    private import semmle.javascript.dataflow.internal.Contents::Private as ContentPrivate
     private import LabelImpl
 
     private module LabelImpl {
@@ -1676,7 +1685,7 @@ module API {
           or
           content instanceof ContentPrivate::MkPromiseError and result = "getPromisedError()"
           or
-          content instanceof ContentPrivate::MkArrayElementUnknown and result = "getUnknownMember()"
+          content instanceof ContentPrivate::MkArrayElementUnknown and result = "getArrayElement()"
         }
 
         override string toString() {

javascript/ql/lib/semmle/javascript/frameworks/D3.qll

@@ -80,7 +80,7 @@ module D3 {
       or
       this = d3Selection().getMember("node").getReturn().asSource()
       or
-      this = d3Selection().getMember("nodes").getReturn().getUnknownMember().asSource()
+      this = d3Selection().getMember("nodes").getReturn().getArrayElement().asSource()
     }
   }
 

javascript/ql/lib/semmle/javascript/frameworks/Puppeteer.qll

@@ -32,7 +32,7 @@ module Puppeteer {
     or
     result = [browser(), context()].getMember("newPage").getReturn().getPromised()
     or
-    result = [browser(), context()].getMember("pages").getReturn().getPromised().getUnknownMember()
+    result = [browser(), context()].getMember("pages").getReturn().getPromised().getArrayElement()
     or
     result = target().getMember("page").getReturn().getPromised()
   }
@@ -45,7 +45,7 @@ module Puppeteer {
     or
     result = [page(), browser()].getMember("target").getReturn()
     or
-    result = context().getMember("targets").getReturn().getUnknownMember()
+    result = context().getMember("targets").getReturn().getArrayElement()
     or
     result = target().getMember("opener").getReturn()
   }
@@ -58,7 +58,7 @@ module Puppeteer {
     or
     result = [page(), target()].getMember("browserContext").getReturn()
     or
-    result = browser().getMember("browserContexts").getReturn().getUnknownMember()
+    result = browser().getMember("browserContexts").getReturn().getArrayElement()
     or
     result = browser().getMember("createIncognitoBrowserContext").getReturn().getPromised()
     or

javascript/ql/lib/semmle/javascript/frameworks/Vuex.qll

@@ -104,8 +104,7 @@ module Vuex {
       storeName = this.getNamespace() + localName
       or
       // mapGetters(['foo', 'bar'])
-      this.getLastParameter().getUnknownMember().getAValueReachingSink().getStringValue() =
-        localName and
+      this.getLastParameter().getArrayElement().getAValueReachingSink().getStringValue() = localName and
       storeName = this.getNamespace() + localName
       or
       // mapGetters({foo: 'bar'})

javascript/ql/lib/semmle/javascript/frameworks/data/internal/ApiGraphModelsSpecific.qll

@@ -368,7 +368,7 @@ bindingset[pred]
 predicate apiGraphHasEdge(API::Node pred, string path, API::Node succ) {
   exists(string name | succ = pred.getMember(name) and path = "Member[" + name + "]")
   or
-  succ = pred.getUnknownMember() and path = "AnyMember"
+  succ = pred.getUnknownArrayElement() and path = "ArrayElement"
   or
   succ = pred.getInstance() and path = "Instance"
   or

javascript/ql/lib/semmle/javascript/internal/CachedStages.qll

@@ -297,13 +297,12 @@ module Stages {
       exists(
         API::moduleImport("foo")
             .getMember("bar")
-            .getUnknownMember()
+            .getArrayElement()
             .getAMember()
             .getAParameter()
             .getPromised()
             .getReturn()
             .getParameter(2)
-            .getUnknownMember()
             .getInstance()
             .getReceiver()
             .getForwardingFunction()

javascript/ql/lib/semmle/javascript/security/dataflow/ExternalAPIUsedWithUntrustedDataCustomizations.qll

@@ -179,7 +179,6 @@ module ExternalApiUsedWithUntrustedData {
       or
       exists(string member |
         node = base.getMember(member) and
-        not node = base.getUnknownMember() and
         not isNumericString(member) and
         not (member = "default" and base = API::moduleImport(_)) and
         not member = "then" // use the 'promised' edges for .then callbacks
@@ -189,10 +188,7 @@ module ExternalApiUsedWithUntrustedData {
         else result = basename + "['" + member.regexpReplaceAll("'", "\\'") + "']"
       )
       or
-      (
-        node = base.getUnknownMember() or
-        node = base.getMember(any(string s | isNumericString(s)))
-      ) and
+      node = base.getArrayElement() and
       result = basename + "[]"
       or
       // just collapse promises

javascript/ql/src/experimental/Security/CWE-347/JWT.qll

@@ -7,7 +7,7 @@ DataFlow::Node unverifiedDecode() {
     verify
         .getParameter(2)
         .getMember("algorithms")
-        .getUnknownMember()
+        .getArrayElement()
         .asSink()
         .mayHaveStringValue("none") and
     result = verify.getParameter(0).asSink()
@@ -32,7 +32,7 @@ DataFlow::Node verifiedDecode() {
       not verify
           .getParameter(2)
           .getMember("algorithms")
-          .getUnknownMember()
+          .getArrayElement()
           .asSink()
           .mayHaveStringValue("none") or
       not exists(verify.getParameter(2).getMember("algorithms"))

javascript/ql/src/experimental/semmle/javascript/Execa.qll

@@ -72,7 +72,7 @@ module Execa {
     override predicate isShellInterpreted(DataFlow::Node arg) {
       // if shell: true then first and second args are sinks
       // options can be third argument
-      arg = [this.getArgument(0), this.getParameter(1).getUnknownMember().asSink()] and
+      arg = [this.getArgument(0), this.getParameter(1).getArrayElement().asSink()] and
       isExecaShellEnable(this.getParameter(2))
       or
       // options can be second argument