cookiejack15 opened a new issue, #146:
URL: https://github.com/apache/logging-log4j-kotlin/issues/146
## Bug Description
`ContextStack.push(message, vararg args)` delegates to
`ThreadContext.push(message, args)` **without the Kotlin spread operator
(`*`)**. This causes the `args` array to be wrapped inside another array when
passed to the Java varargs method, resulting in systematically corrupted
context stack entries for every parameterized call.
**Affected file:**
`log4j-api-kotlin/src/main/kotlin/org/apache/logging/log4j/kotlin/ContextStack.kt`
(line 106)
**Introduced in:** 1.3.0 (when ContextStack facade was added)
**Affected versions:** 1.3.0, 1.4.0, 1.5.0 (current latest), 1.6.0-SNAPSHOT
## Root Cause
In Kotlin, when passing an array to a Java varargs method, the spread
operator `*` is required to unpack the array into individual varargs elements.
Without it, the Kotlin compiler wraps the entire array as a single element of a
new array.
**Current code (buggy):**
```kotlin
fun push(message: String, vararg args: Any?) = ThreadContext.push(message,
args)
```
**Expected code (fix):**
```kotlin
fun push(message: String, vararg args: Any?) = ThreadContext.push(message,
*args)
```
## What Happens
When a user calls:
```kotlin
ContextStack.push("requestId={} userId={}", "req-123", "user-42")
```
1. Kotlin creates the vararg array: `args = Object[]{"req-123", "user-42"}`
2. Without `*`, the call compiles to: `ThreadContext.push(message, new
Object[] { new Object[]{"req-123", "user-42"} })`
3. The args array is wrapped inside another array — Java's varargs receives
**one** argument (the inner array) instead of two separate strings
**Actual output:** `requestId=[req-123, user-42] userId={}`
**Expected output:** `requestId=req-123 userId=user-42`
Even single-parameter calls are corrupted:
```kotlin
ContextStack.push("userId={}", "user-42")
// Actual: "userId=[user-42]"
// Expected: "userId=user-42"
```
## Proof of Concept
```kotlin
import org.apache.logging.log4j.kotlin.ContextStack
fun main() {
// Multi-parameter: all values merged, second value lost
ContextStack.push("requestId={} userId={}", "req-abc-123", "user-42")
println(ContextStack.peek())
// Actual: "requestId=[req-abc-123, user-42] userId={}"
// Expected: "requestId=req-abc-123 userId=user-42"
ContextStack.pop()
// Single parameter: brackets injected
ContextStack.push("userId={}", "user-42")
println(ContextStack.peek())
// Actual: "userId=[user-42]"
// Expected: "userId=user-42"
ContextStack.pop()
// Three parameters: 2nd and 3rd entirely lost
ContextStack.push("a={} b={} c={}", "1", "2", "3")
println(ContextStack.peek())
// Actual: "a=[1, 2, 3] b={} c={}"
// Expected: "a=1 b=2 c=3"
ContextStack.pop()
}
```
## Unit Test
```kotlin
import org.apache.logging.log4j.kotlin.ContextStack
import org.junit.jupiter.api.AfterEach
import org.junit.jupiter.api.Test
import kotlin.test.assertEquals
class ContextStackPushTest {
@AfterEach
fun tearDown() {
ContextStack.clear()
}
@Test
fun `parameterized push loses second parameter`() {
ContextStack.push("user={} action={}", "admin", "login")
assertEquals("user=admin action=login", ContextStack.peek())
}
@Test
fun `single parameter push corrupts value format`() {
ContextStack.push("user={}", "admin")
assertEquals("user=admin", ContextStack.peek())
}
@Test
fun `three parameters - values lost from designated fields`() {
ContextStack.push("a={} b={} c={}", "1", "2", "3")
assertEquals("a=1 b=2 c=3", ContextStack.peek())
}
}
```
## Proposed Fix
One-character fix — add the spread operator `*`:
```diff
- fun push(message: String, vararg args: Any?) = ThreadContext.push(message,
args)
+ fun push(message: String, vararg args: Any?) = ThreadContext.push(message,
*args)
```
## Impact
- The bug is **systematic** — 100% of parameterized `ContextStack.push()`
calls produce corrupted output
- The bug is **silent** — no exception, no warning, corrupted data is
silently pushed
- Context data used for log correlation, audit trails, and request tracing
is corrupted or lost
- The method has been non-functional for its intended purpose since its
introduction in 1.3.0
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