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      • Repair plugins

      Repair plugins post-process the Markdown AST before it becomes HAST. They can repair incomplete syntax, tidy node boundaries, or add temporary presentation without changing the source string.

      Declare a plugin

      Add a small indicator after the content while a response is arriving, then remove it when the response finishes:

      import type {
  RepairPluginRunner,
  RepairPluginSystemConfig,
} from '@fluxdown/types';

import { BaseRepairPlugin } from '@fluxdown/core-plugins/plugins/repair/base';
import { PluginPriority } from '@fluxdown/types';

class StreamingIndicatorPlugin extends BaseRepairPlugin {
  static readonly key = 'repair-streaming-indicator';

  readonly config: RepairPluginSystemConfig = {
    ending: true,
    priority: PluginPriority.Lowest,
  };

  readonly runner: RepairPluginRunner = ({ node, break: stop }) => {
    if (node.type !== 'root' || !('children' in node)) {
      return;
    }

    node.children.push({
      type: 'html',
      value: '<span class="indicator"></span>',
    });

    stop();
  };
}

const repairs = [StreamingIndicatorPlugin];

      After the built-in repairs, this plugin appends an HTML node with the indicator class to the current trailing block. stop() ends the traversal so it is inserted just once.

      Connect to Core

      Add repairs to the Core inputs from the quick start, and enable build.repair and build.repairEnding.

      ending: true limits the plugin to the last block while it is still being generated. Set repairEnding to false when the response finishes to remove the indicator. The original Markdown stays unchanged.

      The built-in HTML processing already allows the class attribute on span. With an HTML renderer, a little CSS gives the indicator its shape:

      .indicator {
  display: inline-block;
  width: 0.5em;
  height: 0.5em;
  border-radius: 50%;
  background: currentColor;
  opacity: 0.45;
}

      Put traversal settings in config and keep constructor options in a separate field. Core runs the plugin and manages its lifecycle.

      Supported plugins

      Append a subpath from the table to @fluxdown/core-plugins/plugins/repair/ to import a plugin. For example, incomplete-image becomes @fluxdown/core-plugins/plugins/repair/incomplete-image.

      A check marks plugins included in PRESET_REPAIR_PLUGINS, exported from @fluxdown/core-plugins/presets/repair. Core registers these automatically; add plugins without a check explicitly.

      build.repair controls repairs. The first group below handles temporary states at the end of a stream and also requires build.repairEnding.

      The streaming tail

      PluginSubpathBuilt inPurpose
      TrailingEscapeRepairPlugintrailing-escapeTemporarily hides a trailing backslash that has not yet formed an escape sequence.
      TrailingEmptyCodeBlockRepairPlugintrailing-empty-code-blockHides a trailing code fence that has no language or content yet.
      IncompleteCodeFenceRepairPluginincomplete-code-fenceHides unfinished trailing fence backticks so they do not appear inside the code.
      IncompleteInlineCodeRepairPluginincomplete-inline-codePresents unfinished inline code as code before its closing backtick arrives.
      IncompleteImageRepairPluginincomplete-imageCreates a placeholder for an unfinished image, or hides it with strategy: 'discard'.
      IncompleteLinkRepairPluginincomplete-linkPresents an unfinished link's text while waiting for the URL to complete.
      TrailingEmptyHeadingRepairPlugintrailing-empty-headingHides a trailing level-one heading that contains only # and no text.
      IncompleteStrongRepairPluginincomplete-strongPresents bold content before its closing delimiter arrives.
      IncompleteEmphasisRepairPluginincomplete-emphasisPresents italic content opened with an asterisk before it is closed.
      IncompleteListMarkerRepairPluginincomplete-list-markerHides a trailing list marker while waiting for the item's content.
      DanglingFootnoteRepairPlugindangling-footnoteTemporarily hides unresolved and incomplete trailing footnote references; requires build.footnote.

      Formatting boundaries

      These plugins run when build.repair is enabled and do not require repairEnding.

      PluginSubpathBuilt inPurpose
      IncompleteHtmlTagRepairPluginincomplete-html-tagHides an unfinished HTML tag fragment at the end of the content.
      RedundantBreakBeforeHtmlRepairPluginredundant-break-before-htmlRemoves redundant line-break nodes before HTML fragments.
      HtmlBoundaryLineBreakRepairPluginhtml-boundary-line-breakPreserves intended line breaks where text meets HTML.
      ParagraphHtmlClosureRepairPluginparagraph-html-closureCloses HTML tags in completed paragraphs so they do not affect later content.
      RedundantTrailingBreakRepairPluginredundant-trailing-breakRemoves redundant trailing line breaks.
      AdjacentTextRepairPluginadjacent-textMerges adjacent text and removes empty text after repairs.

      Repairs affect the current presentation, not the original Markdown stored by your app.