Remove double negations for checkCancellation function (#98)

# Remove double negations for `checkCancellation` function


## ♻️ Current situation & Problem

As mentionned in issue #83 as well as in the PR [#81
(discussion)](#81 (comment)),
the SpeziLLM package is currently using a double negation (`guard`
followed by `!`) for every `checkCancellation()` function call. As
double negations make the code harder to read, we could use `if`
instead.

## ⚙️ Release Notes 
* Remove the double negations for `checkCancellation` by replacing the
`guard` statements that are followed by a not operator into an `if`
statement.

## 📝 Code of Conduct & Contributing Guidelines 

By submitting creating this pull request, you agree to follow our [Code
of
Conduct](https://github.com/StanfordSpezi/.github/blob/main/CODE_OF_CONDUCT.md)
and [Contributing
Guidelines](https://github.com/StanfordSpezi/.github/blob/main/CONTRIBUTING.md):
- [x] I agree to follow the [Code of
Conduct](https://github.com/StanfordSpezi/.github/blob/main/CODE_OF_CONDUCT.md)
and [Contributing
Guidelines](https://github.com/StanfordSpezi/.github/blob/main/CONTRIBUTING.md).

Sources/SpeziLLM/Mock/LLMMockSession.swift

@@ -48,7 +48,7 @@ public final class LLMMockSession: LLMSession, @unchecked Sendable {
                 self.state = .loading
             }
             try? await Task.sleep(for: .seconds(1))
-            guard await !checkCancellation(on: continuation) else {
+            if await checkCancellation(on: continuation) {
                 return
             }
 
@@ -60,7 +60,7 @@ public final class LLMMockSession: LLMSession, @unchecked Sendable {
             let tokens = ["Mock ", "Message ", "from ", "SpeziLLM!"]
             for token in tokens {
                 try? await Task.sleep(for: .milliseconds(500))
-                guard await !checkCancellation(on: continuation) else {
+                if await checkCancellation(on: continuation) {
                     return
                 }
                 await injectAndYield(token, on: continuation)

Sources/SpeziLLMFog/LLMFogSession+Generation.swift

@@ -37,7 +37,7 @@ extension LLMFogSession {
 
         do {
             for try await streamResult in chatStream {
-                guard await !checkCancellation(on: continuation) else {
+                if await checkCancellation(on: continuation) {
                     Self.logger.debug("SpeziLLMFog: LLM inference cancelled because of Task cancellation.")
                     return
                 }

Sources/SpeziLLMLocal/LLMLocalSession+Generate.swift

@@ -51,7 +51,7 @@ extension LLMLocalSession {
 
         MLXRandom.seed(self.schema.parameters.seed ?? UInt64(Date.timeIntervalSinceReferenceDate * 1000))
 
-        guard await !checkCancellation(on: continuation) else {
+        if await checkCancellation(on: continuation) {
             return
         }
 
@@ -163,7 +163,7 @@ extension LLMLocalSession {
 
         for token in tokens {
             try? await Task.sleep(for: .seconds(1))
-            guard await !checkCancellation(on: continuation) else {
+            if await checkCancellation(on: continuation) {
                 return
             }
             continuation.yield(token)

Sources/SpeziLLMLocal/LLMLocalSession.swift

@@ -132,7 +132,7 @@ public final class LLMLocalSession: LLMSession, @unchecked Sendable {
                 }
             }
 
-            guard await !checkCancellation(on: continuation) else {
+            if await checkCancellation(on: continuation) {
                 return
             }
 

Sources/SpeziLLMOpenAI/LLMOpenAISession+Generation.swift

@@ -50,7 +50,7 @@ extension LLMOpenAISession {
                         continue
                     }
 
-                    guard await !checkCancellation(on: continuation) else {
+                    if await checkCancellation(on: continuation) {
                         Self.logger.debug("SpeziLLMOpenAI: LLM inference cancelled because of Task cancellation.")
                         return
                     }
@@ -148,7 +148,7 @@ extension LLMOpenAISession {
                                 // Errors thrown by the functions are surfaced to the user as an LLM generation error
                                 functionCallResponse = try await function.execute()
                             } catch is CancellationError {
-                                guard await !self.checkCancellation(on: continuation) else {
+                                if await self.checkCancellation(on: continuation) {
                                     Self.logger.debug("SpeziLLMOpenAI: Function call execution cancelled because of Task cancellation.")
                                     throw CancellationError()
                                 }

Sources/SpeziLLMOpenAI/LLMOpenAISession.swift

@@ -140,7 +140,7 @@ public final class LLMOpenAISession: LLMSession, @unchecked Sendable {
                 }
             }
 
-            guard await !checkCancellation(on: continuation) else {
+            if await checkCancellation(on: continuation) {
                 return
             }