视口外的超低滚动条

Question

我的角度应用程序中有一个侧边栏导航，该侧边栏具有可折叠项（菜单内的菜单），其中某些菜单包含许多项，我需要滚动条进行导航。我用overflow:auto来“动态”显示滚动条，就像我说的那样，这很好，但是滚动条似乎在视口之外垂直调整大小，几乎与“扩展”内容的终止位置有关，所以看不到向下箭头。我正在使用scss，

  .sidebar-scroll {
   height: 100%;
   border-top: 1px solid black;
   overflow: auto;
   }

我应该注意，.sidebar-scroll在侧边栏的另一个元素中，实际上仅用于常规颜色和样式。这是此组件的整个scss。

@import 'src/assets/scss/functions';
@import 'src/assets/scss/variables';
@import 'src/assets/scss/mixins';

.sidebar {
  position: fixed;
  width: $sidebar-width;
  background-color: $light;
  box-shadow: 0 2px 5px 0 rgba(0, 0, 0, 0.16), 0 2px 10px 0 rgba(0, 0, 0, 0.12);
  left: 0;
  top: 0;
  height: 100%;
  z-index: $zindex-fixed;
  background-image: url("#{$image-path}sidenav.jpg");
  background-size: cover;
  background-repeat: no-repeat;
  background-position: center;
  & > * {
    z-index: 2;
    position: relative;
  }
  &:after {
    content: '';
    background-color: rgba(255, 255, 255, 0.8);
    position: absolute;
    left: 0;
    top: 0;
    z-index: 1;
    @include size(100%);
  }
  .navbar-brand {
    display: block;
    margin: 1.5rem 0;
    padding: 0.5rem;
    color: $body-color;
  }
  .form-group {
    position: relative;
    .form-control {
      border-radius: 0;
      border-left: 0;
      border-right: 0;
      font-weight: 100;
      font-size: $font-size-base;
    }
    .btn {
      position: absolute;
      border-radius: 0;
      background-color: transparent;
      right: 0;
      top: 0;
      font-size: $font-size-base;
      height: 100%;
      color: $gray-600;
      &:hover {
        color: $body-color;
      }
    }
    & *:focus {
      box-shadow: none;
    }
  }
  .nav {
    .nav-item {
      .nav-link {
        color: $body-color;
        font-size: $font-size-sm;
        line-height: 1.5;
        &:hover {
          background-color: rgba(0, 0, 0, 0.05);
        }
        .fa {
          float: left;
          margin-top: 5px;
          margin-right: $sidenav-icon-margin;
          width: $sidenav-icon-size;
          & ~ .fa {
            float: right;
            margin-left: 10px;
            margin-right: 0;
          }
        }
        &.active {
          color: $primary;
        }
      }
      .nav {
        display: block;
        overflow: hidden;
        .nav-link {
          background-color: rgba(95, 93, 93, 0.15);
          padding-left: calc(
            1rem + #{$sidenav-icon-size} + #{$sidenav-icon-margin}
          );
          font-size: ($font-size-sm - 0.05rem);
          &:hover {
            background-color: rgba(0, 0, 0, 0.05);
          }
        }
      }
    }
  }
}
.sidebar-scroll {
  height: 100%;
  overflow: auto;
}

谢谢。