[clang-tidy] readability-function-size: fix nesting level calculation

Summary:
A followup for D32942.

Malcolm Parsons has provided a valid testcase that the initial version of the check complained about nested `if`'s.
As it turns out, the culprit is the **partially** un-intentional `switch` fallthrough.
So rewrite the NestingThreshold logic without ab-using+mis-using that switch with fallthrough, and add testcases with nested `if`' where there should be a warning and shouldn't be a warning. This results in a cleaner, simpler code, too.

I guess, now it would be actually possible to pick some reasonable default for `NestingThreshold` setting.

Fixes PR33454.

Reviewers: malcolm.parsons, alexfh

Reviewed By: malcolm.parsons

Subscribers: sbenza, xazax.hun, cfe-commits, aaron.ballman

Tags: #clang-tools-extra

Differential Revision: https://reviews.llvm.org/D34202

llvm-svn: 305554

1 files changed, 54 insertions, 3 deletions

diff --git a/clang-tools-extra/test/clang-tidy/readability-function-size.cpp b/clang-tools-extra/test/clang-tidy/readability-function-size.cpp
index 9a07eae7628..c75f5b6b70f 100644
--- a/clang-tools-extra/test/clang-tidy/readability-function-size.cpp
+++ b/clang-tools-extra/test/clang-tidy/readability-function-size.cpp
@@ -63,8 +63,9 @@ void bar2() { class A { void barx() {;;} }; }
 #define macro() {int x; {int y; {int z;}}}
 
 void baz0() { // 1
-// CHECK-MESSAGES: :[[@LINE-1]]:6: warning: function 'baz0' exceeds recommended size/complexity
-// CHECK-MESSAGES: :[[@LINE-2]]:6: note: 9 statements (threshold 0)
+  // CHECK-MESSAGES: :[[@LINE-1]]:6: warning: function 'baz0' exceeds recommended size/complexity
+  // CHECK-MESSAGES: :[[@LINE-2]]:6: note: 27 lines including whitespace and comments (threshold 0)
+  // CHECK-MESSAGES: :[[@LINE-3]]:6: note: 9 statements (threshold 0)
   int a;
   { // 2
     int b;
@@ -87,5 +88,55 @@ void baz0() { // 1
   }
   macro()
 // CHECK-MESSAGES: :[[@LINE-1]]:3: note: nesting level 3 starts here (threshold 2)
-// CHECK-MESSAGES: :[[@LINE-27]]:25: note: expanded from macro 'macro'
+// CHECK-MESSAGES: :[[@LINE-28]]:25: note: expanded from macro 'macro'
+}
+
+// check that nested if's are not reported. this was broken initially
+void nesting_if() { // 1
+  // CHECK-MESSAGES: :[[@LINE-1]]:6: warning: function 'nesting_if' exceeds recommended size/complexity
+  // CHECK-MESSAGES: :[[@LINE-2]]:6: note: 22 lines including whitespace and comments (threshold 0)
+  // CHECK-MESSAGES: :[[@LINE-3]]:6: note: 18 statements (threshold 0)
+  // CHECK-MESSAGES: :[[@LINE-4]]:6: note: 6 branches (threshold 0)
+  if (true) { // 2
+     int j;
+  } else if (true) { // 2
+     int j;
+     if (true) { // 3
+       // CHECK-MESSAGES: :[[@LINE-1]]:16: note: nesting level 3 starts here (threshold 2)
+       int j;
+     }
+  } else if (true) { // 2
+     int j;
+     if (true) { // 3
+       // CHECK-MESSAGES: :[[@LINE-1]]:16: note: nesting level 3 starts here (threshold 2)
+       int j;
+     }
+  } else if (true) { // 2
+     int j;
+  }
+}
+
+// however this should warn
+void bad_if_nesting() { // 1
+// CHECK-MESSAGES: :[[@LINE-1]]:6: warning: function 'bad_if_nesting' exceeds recommended size/complexity
+// CHECK-MESSAGES: :[[@LINE-2]]:6: note: 22 lines including whitespace and comments (threshold 0)
+// CHECK-MESSAGES: :[[@LINE-3]]:6: note: 12 statements (threshold 0)
+// CHECK-MESSAGES: :[[@LINE-4]]:6: note: 4 branches (threshold 0)
+  if (true) {    // 2
+    int j;
+  } else { // 2
+    if (true) { // 3
+      // CHECK-MESSAGES: :[[@LINE-1]]:15: note: nesting level 3 starts here (threshold 2)
+      int j;
+    } else { // 3
+      // CHECK-MESSAGES: :[[@LINE-1]]:12: note: nesting level 3 starts here (threshold 2)
+      if (true) { // 4
+        int j;
+      } else { // 4
+        if (true) { // 5
+          int j;
+        }
+      }
+    }
+  }
 }