provide Twig type for "loop" variable inside "foreach"

src/main/java/fr/adrienbrault/idea/symfony2plugin/templating/util/TwigTypeResolveUtil.java

@@ -25,6 +25,7 @@
 import fr.adrienbrault.idea.symfony2plugin.templating.variable.TwigTypeContainer;
 import fr.adrienbrault.idea.symfony2plugin.templating.variable.collector.StaticVariableCollector;
 import fr.adrienbrault.idea.symfony2plugin.templating.variable.dict.PsiVariable;
+import fr.adrienbrault.idea.symfony2plugin.templating.variable.resolver.ForEachLoopResolver;
 import fr.adrienbrault.idea.symfony2plugin.templating.variable.resolver.FormFieldResolver;
 import fr.adrienbrault.idea.symfony2plugin.templating.variable.resolver.FormVarsResolver;
 import fr.adrienbrault.idea.symfony2plugin.templating.variable.resolver.TwigTypeResolver;
@@ -83,6 +84,7 @@ public class TwigTypeResolveUtil {
     private static TwigTypeResolver[] TWIG_TYPE_RESOLVERS = new TwigTypeResolver[] {
         new FormVarsResolver(),
         new FormFieldResolver(),
+        new ForEachLoopResolver(),
     };
 
     @NotNull
@@ -366,6 +368,8 @@ private static void collectForArrayScopeVariables(@NotNull PsiElement psiElement
             return;
         }
 
+        globalVars.put("loop", new PsiVariable("\\loop"));
+
         // {% for user in "users" %}
         PsiElement forTag = twigCompositeElement.getFirstChild();
         PsiElement inVariable = PsiElementUtils.getChildrenOfType(forTag, TwigPattern.getForTagInVariablePattern());

src/main/java/fr/adrienbrault/idea/symfony2plugin/templating/variable/TwigTypeContainer.java

@@ -47,6 +47,11 @@ public static Collection<TwigTypeContainer> fromCollection(Project project, Coll
             if(phpClass.size() > 0) {
                 twigTypeContainerList.add(new TwigTypeContainer(phpClass.iterator().next()));
             }
+
+            // inside {% for ... %}{% endfor %} we have a "loop" var; fake an internal type here
+            if (phpNamedElement.getTypes().contains("\\loop")) {
+                twigTypeContainerList.add(new TwigTypeContainer("\\loop"));
+            }
         }
 
         return twigTypeContainerList;

src/main/java/fr/adrienbrault/idea/symfony2plugin/templating/variable/resolver/ForEachLoopResolver.java

@@ -0,0 +1,34 @@
+package fr.adrienbrault.idea.symfony2plugin.templating.variable.resolver;
+
+import fr.adrienbrault.idea.symfony2plugin.templating.variable.TwigTypeContainer;
+import fr.adrienbrault.idea.symfony2plugin.templating.variable.dict.PsiVariable;
+import org.jetbrains.annotations.Nullable;
+
+import java.util.Collection;
+import java.util.List;
+
+/**
+ * Provide the loop.XXX types inside foreach block if previous element is named loop with the type "\loop" {% for ... %}{% endfor %}
+ *
+ * @author Daniel Espendiller <[email protected]>
+ */
+public class ForEachLoopResolver implements TwigTypeResolver {
+
+    /**
+     * @link https://twig.symfony.com/doc/3.x/tags/for.html#the-loop-variable
+     */
+    public static final String[] LOOP_VARIABLES = {
+        "index", "index0", "revindex", "revindex0", "first", "last", "length", "parent"
+    };
+
+    @Override
+    public void resolve(Collection<TwigTypeContainer> targets, @Nullable Collection<TwigTypeContainer> previousElement, String typeName, Collection<List<TwigTypeContainer>> previousElements, @Nullable Collection<PsiVariable> psiVariables) {
+        if (previousElement == null || previousElement.stream().noneMatch(p -> "\\loop".equals(p.getStringElement()))) {
+            return;
+        }
+
+        for(String string: LOOP_VARIABLES) {
+            targets.add(new TwigTypeContainer(string));
+        }
+    }
+}

src/test/java/fr/adrienbrault/idea/symfony2plugin/tests/templating/util/TwigTypeResolveUtilTest.java

@@ -9,11 +9,15 @@
 import com.jetbrains.twig.TwigFileType;
 import com.jetbrains.twig.TwigLanguage;
 import fr.adrienbrault.idea.symfony2plugin.templating.util.TwigTypeResolveUtil;
+import fr.adrienbrault.idea.symfony2plugin.templating.variable.TwigTypeContainer;
 import fr.adrienbrault.idea.symfony2plugin.templating.variable.dict.PsiVariable;
 import fr.adrienbrault.idea.symfony2plugin.tests.SymfonyLightCodeInsightFixtureTestCase;
 import org.jetbrains.annotations.NotNull;
 
+import java.util.Collection;
 import java.util.Map;
+import java.util.Set;
+import java.util.stream.Collectors;
 
 /**
  * @author Daniel Espendiller <[email protected]>
@@ -84,6 +88,41 @@ public void testCollectScopeVariables() {
         assertContainsElements(stringPsiVariableMap.get("b").getTypes(), "\\Foo\\Bar");
     }
 
+    /**
+     * @see TwigTypeResolveUtil#collectScopeVariables
+     */
+    public void testForeachMustProvideLoopVariable() {
+        myFixture.configureByText(TwigFileType.INSTANCE,
+            "{% for foo in foo %}" +
+                "{{ <caret> }}" +
+                "{% endfor %}"
+        );
+
+        PsiElement psiElement = myFixture.getFile().findElementAt(myFixture.getCaretOffset());
+
+        Map<String, PsiVariable> stringPsiVariableMap = TwigTypeResolveUtil.collectScopeVariables(psiElement);
+        assertContainsElements(stringPsiVariableMap.keySet(), "loop");
+    }
+
+    /**
+     * @see TwigTypeResolveUtil#resolveTwigMethodName
+     */
+    public void testForeachMustProvideLoopTypeVariable() {
+        myFixture.configureByText(TwigFileType.INSTANCE,
+            "{% for foo in foo %}" +
+                "{{ loop.i<caret> }}" +
+                "{% endfor %}"
+        );
+
+        PsiElement psiElement = myFixture.getFile().findElementAt(myFixture.getCaretOffset());
+        Collection<String> beforeLeaf = TwigTypeResolveUtil.formatPsiTypeName(psiElement);
+
+        Collection<TwigTypeContainer> stringPsiVariableMap = TwigTypeResolveUtil.resolveTwigMethodName(psiElement.getPrevSibling(), beforeLeaf);
+
+        Set<String> types = stringPsiVariableMap.stream().map(TwigTypeContainer::getStringElement).collect(Collectors.toSet());
+        assertContainsElements(types, "last", "index", "index0");
+    }
+
     private void assertMatches(@NotNull String content, @NotNull String... regularExpressions) {
         for (String regularExpression : regularExpressions) {
             if(content.matches(regularExpression)) {