From d144ea2f1ccdce53e775ac2b67b211762aff7700 Mon Sep 17 00:00:00 2001
From: Anders Schack-Mulligen <schack@semmle.com>
Date: Thu, 4 Apr 2019 11:01:00 +0200
Subject: [PATCH] Java: Exclude slf4j calls in PrintLnArray as it supports
 array formatting.

---
 change-notes/1.21/analysis-java.md                          | 1 +
 .../Undesirable Calls/PrintLnArray.ql                       | 6 +++++-
 java/ql/src/semmle/code/java/StringFormat.qll               | 3 +++
 3 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/change-notes/1.21/analysis-java.md b/change-notes/1.21/analysis-java.md
index 523c227e26e..efd4b302ae3 100644
--- a/change-notes/1.21/analysis-java.md
+++ b/change-notes/1.21/analysis-java.md
@@ -9,6 +9,7 @@
 
 | **Query**                  | **Expected impact**    | **Change**                                                       |
 |----------------------------|------------------------|------------------------------------------------------------------|
+| Implicit conversion from array to string (`java/print-array`) | Fewer false positive results | Results in slf4j logging calls are no longer reported as slf4j supports array printing. |
 
 ## Changes to QL libraries
 
diff --git a/java/ql/src/Violations of Best Practice/Undesirable Calls/PrintLnArray.ql b/java/ql/src/Violations of Best Practice/Undesirable Calls/PrintLnArray.ql
index d778dc4ce7a..a89b3b0cbea 100644
--- a/java/ql/src/Violations of Best Practice/Undesirable Calls/PrintLnArray.ql	
+++ b/java/ql/src/Violations of Best Practice/Undesirable Calls/PrintLnArray.ql	
@@ -27,7 +27,11 @@ predicate arraysToStringArgument(Expr e) {
 from Expr arr
 where
   arr.getType() instanceof Array and
-  implicitToStringCall(arr)
+  implicitToStringCall(arr) and
+  not exists(FormattingCall fmtcall |
+    // exclude slf4j formatting as it supports array formatting
+    fmtcall.getAnArgumentToBeFormatted() = arr and fmtcall.getSyntax().isLogger()
+  )
   or
   arr.getType().(Array).getComponentType() instanceof Array and
   arraysToStringArgument(arr)
diff --git a/java/ql/src/semmle/code/java/StringFormat.qll b/java/ql/src/semmle/code/java/StringFormat.qll
index dcfb71e229e..09fa7a9ee17 100644
--- a/java/ql/src/semmle/code/java/StringFormat.qll
+++ b/java/ql/src/semmle/code/java/StringFormat.qll
@@ -85,6 +85,9 @@ class FmtSyntax extends TFmtSyntax {
     or
     result = "logger ({}) syntax" and this = TFmtLogger()
   }
+
+  /** Holds if this syntax is logger ({}) syntax. */
+  predicate isLogger() { this = TFmtLogger() }
 }
 
 /**