PHPLIB-1372 Fix RiskyTruthyFalsyComparison (#1218)

The new RiskyTruthyFalsyComparison errors are introduced by psalm 5.20.0.

Disable on example files. Using getenv('MONGODB_URI') ?: 'mongodb://127.0.0.1/' is safe as any falsy value could be replaced by the default URI.
Replace !empty($filter) by $filter !== [] as $filter is an array or an object, and even empty(new stdClass) is true. This might be a necessary bug fix.

Author: GromNaN

psalm.xml.dist

@@ -34,5 +34,13 @@
 
         <!-- This is often the result of type checks due to missing native types -->
         <DocblockTypeContradiction errorLevel="info" />
+
+        <!-- If the result of getenv is falsy, using the default URI is fine -->
+        <RiskyTruthyFalsyComparison>
+            <errorLevel type="suppress">
+                <directory name="examples" />
+                <directory name="docs/examples" />
+            </errorLevel>
+        </RiskyTruthyFalsyComparison>
     </issueHandlers>
 </psalm>

src/ChangeStream.php

@@ -262,7 +262,7 @@ private function onIteration(bool $incrementKey): void
      */
     private function resume(): void
     {
-        if (! $this->resumeCallable) {
+        if ($this->resumeCallable === null) {
             throw new BadMethodCallException('Cannot resume a closed change stream.');
         }
 

src/Operation/Count.php

@@ -187,7 +187,7 @@ private function createCommandDocument(): array
     {
         $cmd = ['count' => $this->collectionName];
 
-        if (! empty($this->filter)) {
+        if ($this->filter !== []) {
             $cmd['query'] = (object) $this->filter;
         }
 

src/Operation/Distinct.php

@@ -182,7 +182,7 @@ private function createCommandDocument(): array
             'key' => $this->fieldName,
         ];
 
-        if (! empty($this->filter)) {
+        if ($this->filter !== []) {
             $cmd['query'] = (object) $this->filter;
         }