Merge pull request #19726 from Napalys/js/quality/string_interpolation

JS: Promote `js/template-syntax-in-string-literal` to the Code Quality suite.

Author: Napalys

javascript/ql/integration-tests/query-suite/javascript-code-quality.qls.expected

@@ -3,6 +3,7 @@ ql/javascript/ql/src/Declarations/SuspiciousMethodNameDeclaration.ql
 ql/javascript/ql/src/Expressions/ExprHasNoEffect.ql
 ql/javascript/ql/src/Expressions/MissingAwait.ql
 ql/javascript/ql/src/LanguageFeatures/SpuriousArguments.ql
+ql/javascript/ql/src/LanguageFeatures/TemplateSyntaxInStringLiteral.ql
 ql/javascript/ql/src/Quality/UnhandledErrorInStreamPipeline.ql
 ql/javascript/ql/src/RegExp/DuplicateCharacterInCharacterClass.ql
 ql/javascript/ql/src/RegExp/RegExpAlwaysMatches.ql

javascript/ql/src/LanguageFeatures/TemplateSyntaxInStringLiteral.ql

@@ -5,7 +5,10 @@
  * @problem.severity warning
  * @id js/template-syntax-in-string-literal
  * @precision high
- * @tags correctness
+ * @tags quality
+ *       reliability
+ *       correctness
+ *       language-features
  */
 
 import javascript
@@ -74,8 +77,8 @@ class CandidateStringLiteral extends StringLiteral {
  */
 predicate hasObjectProvidingTemplateVariables(CandidateStringLiteral lit) {
   exists(DataFlow::CallNode call, DataFlow::ObjectLiteralNode obj |
-    call.getAnArgument().getALocalSource() = obj and
-    call.getAnArgument().asExpr() = lit and
+    call.getAnArgument() = [lit.flow(), StringConcatenation::getRoot(lit.flow())] and
+    obj.flowsTo(call.getAnArgument()) and
     forex(string name | name = lit.getAReferencedVariable() | exists(obj.getAPropertyWrite(name)))
   )
 }
@@ -91,12 +94,38 @@ VarDecl getDeclIn(Variable v, Scope scope, string name, CandidateTopLevel tl) {
   result.getTopLevel() = tl
 }
 
+/**
+ * Tracks data flow from a string literal that may flow to a replace operation.
+ */
+DataFlow::SourceNode trackStringWithTemplateSyntax(
+  CandidateStringLiteral lit, DataFlow::TypeTracker t
+) {
+  t.start() and result = lit.flow() and exists(lit.getAReferencedVariable())
+  or
+  exists(DataFlow::TypeTracker t2 | result = trackStringWithTemplateSyntax(lit, t2).track(t2, t))
+}
+
+/**
+ * Gets a string literal that flows to a replace operation.
+ */
+DataFlow::SourceNode trackStringWithTemplateSyntax(CandidateStringLiteral lit) {
+  result = trackStringWithTemplateSyntax(lit, DataFlow::TypeTracker::end())
+}
+
+/**
+ * Holds if the string literal flows to a replace method call.
+ */
+predicate hasReplaceMethodCall(CandidateStringLiteral lit) {
+  trackStringWithTemplateSyntax(lit).getAMethodCall() instanceof StringReplaceCall
+}
+
 from CandidateStringLiteral lit, Variable v, Scope s, string name, VarDecl decl
 where
   decl = getDeclIn(v, s, name, lit.getTopLevel()) and
   lit.getAReferencedVariable() = name and
   lit.isInScope(s) and
   not hasObjectProvidingTemplateVariables(lit) and
-  not lit.getStringValue() = "${" + name + "}"
+  not lit.getStringValue() = "${" + name + "}" and
+  not hasReplaceMethodCall(lit)
 select lit, "This string is not a template literal, but appears to reference the variable $@.",
   decl, v.getName()

javascript/ql/src/change-notes/2025-06-12-string-interpolation.md

@@ -0,0 +1,4 @@
+---
+category: minorAnalysis
+---
+* Fixed false positives in the `js/template-syntax-in-string-literal` query where template syntax in string concatenation and "manual string interpolation" patterns were incorrectly flagged.

javascript/ql/src/change-notes/2025-06-12-template-syntax-metadata.md

@@ -0,0 +1,4 @@
+---
+category: queryMetadata
+---
+* Added `reliability` and `language-features` tags to the `js/template-syntax-in-string-literal` query.

javascript/ql/test/query-tests/LanguageFeatures/TemplateSyntaxInStringLiteral/TemplateSyntaxInStringLiteral.js

@@ -40,4 +40,30 @@ function foo1() {
     writer.emit("Name: ${name}, Date: ${date}.", data);
 
     writer.emit("Name: ${name}, Date: ${date}, ${foobar}", data); // $ Alert - `foobar` is not in `data`.
-}
+}
+
+function a(actual, expected, description) {
+    assert(false, "a", description, "expected (" +
+        typeof expected + ") ${expected} but got (" + typeof actual + ") ${actual}", {
+            expected: expected,
+            actual: actual
+        });
+}
+
+function replacer(str, name) {
+    return str.replace("${name}", name);
+}
+
+function replacerAll(str, name) {
+    return str.replaceAll("${name}", name);
+}
+
+function manualInterpolation(name) {
+    let str = "Name: ${name}";
+    let result1 = replacer(str, name);
+    console.log(result1); 
+
+    str = "Name: ${name} and again: ${name}";
+    let result2 = replacerAll(str, name);
+    console.log(result2);
+}