Prevent cycles in layout editor (and detect with lint)

If you specify <style name="Foo" parent="@style/Foo.Bar"/> then the
layout editor hangs with infinite recursion because as it walks up the
parent chains, it first goes from Foo.Bar (thanks to the style
definition), and from there it goes to Foo (because Foo is the implied
parent of Foo.Bar) and so on.

This changeset adds a visited set to the isTheme() method to prevent
boundless recursion in the presence of cycles.

It also adds a check for this condition to the lint style cycle
detector.

This fixes
http://code.google.com/p/android/issues/detail?id=24385
StackOverflowError when opening any layout xml file in Eclipse

Change-Id: I5c52e77ab7e81ea528f3b8fcdd052bff9447b2c9

3 files changed, 22 insertions, 1 deletions

diff --git a/lint/libs/lint_checks/src/com/android/tools/lint/checks/StyleCycleDetector.java b/lint/libs/lint_checks/src/com/android/tools/lint/checks/StyleCycleDetector.java
index 8c1d6d3..77de5ab 100644
--- a/lint/libs/lint_checks/src/com/android/tools/lint/checks/StyleCycleDetector.java
+++ b/lint/libs/lint_checks/src/com/android/tools/lint/checks/StyleCycleDetector.java
@@ -50,7 +50,8 @@ public class StyleCycleDetector extends ResourceXmlDetector {
             8,
             Severity.ERROR,
             StyleCycleDetector.class,
-            Scope.RESOURCE_FILE_SCOPE);
+            Scope.RESOURCE_FILE_SCOPE).setMoreInfo(
+            "http://developer.android.com/guide/topics/ui/themes.html#Inheritance"); //$NON-NLS-1$
 
     /** Constructs a new {@link StyleCycleDetector} */
     public StyleCycleDetector() {
@@ -81,6 +82,13 @@ public class StyleCycleDetector extends ResourceXmlDetector {
                     parent.equals(STYLE_RESOURCE_PREFIX + name)) {
                 context.report(ISSUE, context.getLocation(parentNode),
                         String.format("Style %1$s should not extend itself", name), null);
+            } else if (parent.startsWith(STYLE_RESOURCE_PREFIX)
+                    && parent.startsWith(name, STYLE_RESOURCE_PREFIX.length())
+                    && parent.startsWith(".", STYLE_RESOURCE_PREFIX.length() + name.length())) {
+                context.report(ISSUE, context.getLocation(parentNode),
+                        String.format("Potential cycle: %1$s is the implied parent of %2$s and " +
+                                "this defines the opposite", name,
+                                parent.substring(STYLE_RESOURCE_PREFIX.length())), null);
             }
         }
     }
diff --git a/lint/libs/lint_checks/tests/src/com/android/tools/lint/checks/StyleCycleDetectorTest.java b/lint/libs/lint_checks/tests/src/com/android/tools/lint/checks/StyleCycleDetectorTest.java
index 39126df..f31a26b 100644
--- a/lint/libs/lint_checks/tests/src/com/android/tools/lint/checks/StyleCycleDetectorTest.java
+++ b/lint/libs/lint_checks/tests/src/com/android/tools/lint/checks/StyleCycleDetectorTest.java
@@ -31,4 +31,12 @@ public class StyleCycleDetectorTest extends AbstractCheckTest {
 
             lintProject("res/values/styles.xml"));
     }
+
+    public void test2() throws Exception {
+        assertEquals(
+            "stylecycle.xml:3: Error: Potential cycle: PropertyToggle is the implied parent " +
+            "of PropertyToggle.Base and this defines the opposite",
+
+            lintProject("res/values/stylecycle.xml"));
+    }
 }
diff --git a/lint/libs/lint_checks/tests/src/com/android/tools/lint/checks/data/res/values/stylecycle.xml b/lint/libs/lint_checks/tests/src/com/android/tools/lint/checks/data/res/values/stylecycle.xml
new file mode 100644
index 0000000..448eb9c
--- /dev/null
+++ b/lint/libs/lint_checks/tests/src/com/android/tools/lint/checks/data/res/values/stylecycle.xml
@@ -0,0 +1,5 @@
+<?xml version="1.0" encoding="utf-8"?>
+<resources xmlns:android="http://schemas.android.com/apk/res/android">
+  <style name="PropertyToggle" parent="@style/PropertyToggle.Base"></style>
+  <style name="PropertyToggle.Base"></style>
+</resources>