From f93c01c3a77176c45b22f6d5c0e48641b2da632d Mon Sep 17 00:00:00 2001
From: Yegor Bugayenko <yegor256@gmail.com>
Date: Fri, 7 Feb 2025 13:54:58 +0300
Subject: [PATCH] #320 defect formatting

---
 src/main/java/org/eolang/lints/Defect.java     | 12 ++++++++----
 src/test/java/org/eolang/lints/DefectTest.java | 15 +++++++++++++++
 2 files changed, 23 insertions(+), 4 deletions(-)

diff --git a/src/main/java/org/eolang/lints/Defect.java b/src/main/java/org/eolang/lints/Defect.java
index c2d928d2..a7b0f2b4 100644
--- a/src/main/java/org/eolang/lints/Defect.java
+++ b/src/main/java/org/eolang/lints/Defect.java
@@ -129,10 +129,14 @@ public Default(
 
         @Override
         public String toString() {
-            return String.format(
-                "[%s %s %s]:%d %s",
-                this.prg, this.rle, this.sev, this.lineno, this.txt
-            );
+            final StringBuilder text = new StringBuilder(0)
+                .append('[').append(this.prg).append(' ')
+                .append(this.rle).append(' ')
+                .append(this.sev).append(']');
+            if (this.lineno > 0) {
+                text.append(':').append(this.lineno);
+            }
+            return text.append(' ').append(this.txt).toString();
         }
 
         @Override
diff --git a/src/test/java/org/eolang/lints/DefectTest.java b/src/test/java/org/eolang/lints/DefectTest.java
index b1b8cf2e..1841fce8 100644
--- a/src/test/java/org/eolang/lints/DefectTest.java
+++ b/src/test/java/org/eolang/lints/DefectTest.java
@@ -65,4 +65,19 @@ void printsProgramName() {
             Matchers.hasToString(Matchers.containsString(program))
         );
     }
+
+    @Test
+    void printsWithoutZeroLineNumber() {
+        MatcherAssert.assertThat(
+            "toString() prints zero for line number",
+            new Defect.Default(
+                "foo",
+                Severity.WARNING,
+                "foo.bar",
+                0,
+                "the message"
+            ),
+            Matchers.hasToString(Matchers.not(Matchers.containsString(":0")))
+        );
+    }
 }