replace protocol presence ASSERTs with error returns.

signed-off-by: jcarsey
reviewed-by: lgrosenb

git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@11899 6f19259b-4bc3-4df7-8a09-765794883524

ShellPkg/Library/UefiShellLib/UefiShellLib.c

@@ -483,12 +483,10 @@ ShellOpenFileByDevicePath(
   EFI_FILE_PROTOCOL               *Handle1;
   EFI_FILE_PROTOCOL               *Handle2;
 
-  //
-  // ASERT for FileHandle, FilePath, and DeviceHandle being NULL
-  //
-  ASSERT(FilePath != NULL);
-  ASSERT(FileHandle != NULL);
-  ASSERT(DeviceHandle != NULL);
+  if (FilePath == NULL || FileHandle == NULL || DeviceHandle == NULL) {
+    return (EFI_INVALID_PARAMETER);
+  }
+
   //
   // which shell interface should we use
   //
@@ -601,7 +599,7 @@ ShellOpenFileByDevicePath(
   otherwise, the Filehandle is NULL. The Attributes is valid only for
   EFI_FILE_MODE_CREATE.
 
-  if FileNAme is NULL then ASSERT()
+  if FileName is NULL then ASSERT()
 
   @param  FileName 		  pointer to file name
   @param  FileHandle		pointer to the file handle.
@@ -1047,9 +1045,12 @@ ShellGetExecutionBreakFlag(
   //
   // using EFI Shell; call the function to check
   //
-  ASSERT(mEfiShellEnvironment2 != NULL);
+  if (mEfiShellEnvironment2 != NULL) {
     return (mEfiShellEnvironment2->GetExecutionBreak());
   }
+
+  return (FALSE);
+}
 /**
   return the value of an environment variable
 
@@ -1075,15 +1076,14 @@ ShellGetEnvironmentVariable (
   }
 
   //
-  // ASSERT that we must have EFI shell
-  //
-  ASSERT(mEfiShellEnvironment2 != NULL);
-
-  //
-  // using EFI Shell
+  // Check for EFI shell
   //
+  if (mEfiShellEnvironment2 != NULL) {
     return (mEfiShellEnvironment2->GetEnv((CHAR16*)EnvKey));
   }
+
+  return NULL;
+}
 /**
   set the value of an environment variable
 
@@ -1177,10 +1177,11 @@ ShellExecute (
                                       EnvironmentVariables,
                                       Status));
   }
+
   //
-  // ASSERT that we must have EFI shell
+  // Check for EFI shell
   //
-  ASSERT(mEfiShellEnvironment2 != NULL);
+  if (mEfiShellEnvironment2 != NULL) {
     //
     // Call EFI Shell version (not using EnvironmentVariables or Status parameters)
     // Due to oddity in the EFI shell we want to dereference the ParentHandle here
@@ -1189,6 +1190,9 @@ ShellExecute (
                                           CommandLine,
                                           Output));
   }
+
+  return (EFI_UNSUPPORTED);
+}
 /**
   Retreives the current directory path
 
@@ -1213,6 +1217,7 @@ ShellGetCurrentDir (
   if (mEfiShellProtocol != NULL) {
     return (mEfiShellProtocol->GetCurDir(DeviceName));
   }
+
   //
   // Check for EFI shell
   //
@@ -1251,15 +1256,16 @@ ShellSetPageBreakMode (
       return;
     } else {
       //
-      // ASSERT that must have EFI Shell
+      // Check for EFI shell
       //
-      ASSERT(mEfiShellEnvironment2 != NULL);
+      if (mEfiShellEnvironment2 != NULL) {
         //
         // Enable with EFI Shell
         //
         mEfiShellEnvironment2->EnablePageBreak (DEFAULT_INIT_ROW, DEFAULT_AUTO_LF);
         return;
       }
+    }
   } else {
     //
     // check for UEFI Shell 2.0
@@ -1272,9 +1278,9 @@ ShellSetPageBreakMode (
       return;
     } else {
       //
-      // ASSERT that must have EFI Shell
+      // Check for EFI shell
       //
-      ASSERT(mEfiShellEnvironment2 != NULL);
+      if (mEfiShellEnvironment2 != NULL) {
         //
         // Disable with EFI Shell
         //
@@ -1283,6 +1289,7 @@ ShellSetPageBreakMode (
       }
     }
   }
+}
 
 ///
 /// version of EFI_SHELL_FILE_INFO struct, except has no CONST pointers.
@@ -1463,10 +1470,9 @@ ShellOpenFileMetaArg (
   }
 
   //
-  // ASSERT that we must have EFI shell
+  // Check for EFI shell
   //
-  ASSERT(mEfiShellEnvironment2 != NULL);
-
+  if (mEfiShellEnvironment2 != NULL) {
     //
     // make sure the list head is initialized
     //
@@ -1504,9 +1510,11 @@ ShellOpenFileMetaArg (
       *ListHead = NULL;
       Status = EFI_NOT_FOUND;
     }
-
     return (Status);
   }
+
+  return (EFI_UNSUPPORTED);
+}
 /**
   Free the linked list returned from ShellOpenFileMetaArg.
 
@@ -1534,7 +1542,7 @@ ShellCloseFileMetaArg (
   //
   if (mEfiShellProtocol != NULL) {
     return (mEfiShellProtocol->FreeFileList(ListHead));
-  } else {
+  } else if (mEfiShellEnvironment2 != NULL) {
     //
     // Since this is EFI Shell version we need to free our internally made copy
     // of the list
@@ -1551,6 +1559,8 @@ ShellCloseFileMetaArg (
     }
     return EFI_SUCCESS;
   }
+
+  return (EFI_UNSUPPORTED);
 }
 
 /**