Suppress lint error according to code level markers

src/Linters/HHClientLinter.hack

@@ -11,7 +11,7 @@ namespace Facebook\HHAST;
 
 use type Facebook\HHAST\{BaseLinter};
 use namespace Facebook\TypeAssert;
-use namespace HH\Lib\{C, Vec};
+use namespace HH\Lib\{C, Str, Vec};
 
 /**
  * A linter as a proxy invoking `hh_client --lint`.
@@ -26,6 +26,38 @@ final class HHClientLinter extends BaseLinter {
     'version' => string,
   );
 
+  private function isCodeSuppressed(string $previous_line, int $code): bool {
+    return
+      Str\contains(
+        $previous_line,
+        self::ignoreSingleErrorMarkerOf((string)$code),
+      ) ||
+      Str\contains($previous_line, self::fixmeMarkerOf((string)$code));
+  }
+
+  /**
+   * Is the linter code disabled for the entire file?
+   * Memoized since this should not change per run.
+   */
+  <<__Memoize>>
+  public function isCodeSuppressedForFile(int $code): bool {
+    return Str\contains(
+      $this->getFile()->getContents(),
+      self::ignoreAllMarkerOf((string)$code),
+    );
+  }
+
+  private function isSuppressed(HHClientLintError::TJSONError $error): bool {
+    $previous_line = $this->getLine($error['line'] - 2);
+    if ($previous_line is null) {
+      return false;
+    } else {
+      return $this->isLinterSuppressed($previous_line) ||
+        $this->isCodeSuppressed($previous_line, $error['code']) ||
+        $this->isCodeSuppressedForFile($error['code']);
+    }
+  }
+
   <<__Override>>
   public async function getLintErrorsAsync(
   ): Awaitable<vec<HHClientLintError>> {
@@ -45,9 +77,8 @@ final class HHClientLinter extends BaseLinter {
         \JSON_FB_HACK_ARRAYS,
       ),
     );
-    return Vec\map(
-      $hh_client_lint_result['errors'],
-      $error ==> new HHClientLintError($this, $error),
-    );
+    return $hh_client_lint_result['errors']
+      |> Vec\filter($$, $error ==> !$this->isSuppressed($error))
+      |> Vec\map($$, $error ==> new HHClientLintError($this, $error));
   }
 }

tests/HHClientLinterTest.hack

@@ -24,6 +24,16 @@ final class HHClientLinterTest extends TestCase {
   public function getCleanExamples(): vec<(string)> {
     return vec[
       tuple("<?hh\nclass Foo {}"),
+      tuple(
+        '<?hh
+        function invalid_null_check(): void {
+          $cannot_be_null = 42;
+          // HHAST_FIXME[5611]
+          if ($cannot_be_null is null) {
+            throw new Exception();
+          }
+        }',
+      ),
     ];
   }