serverless-tag-resources/src/template-tagger.js

Datamart: Tag all AWS resources with dual legacy + datamart:* tag support

"use strict";

const { buildListTags, buildDictTags } = require("./tags");
const { classifyResource } = require("./resource-classifier");

/**
 * Template Tagger — Hook: before:package:finalize
 *
 * Mutates the compiled CloudFormation template to inject tags
 * into resource Properties before deployment.
 */

/**
 * Tag all resources in a CloudFormation resources object.
 *
 * @param {object} resources - { LogicalId: { Type, Properties, ... } }
 * @param {object} stackTags - from provider.stackTags
 * @param {string} stage - deployment stage
 * @param {Function} log - logging function
 */
function tagResources(resources, stackTags, stage, log) {
  if (!resources) return;

  for (const [logicalId, resource] of Object.entries(resources)) {
    const resourceType = resource.Type;
    if (!resourceType) continue;

    const classification = classifyResource(resourceType);

    if (classification === "skip") continue;

    if (!resource.Properties) {
      log(`TAGGING: skipping ${resourceType} (${logicalId}) — no Properties`);
      continue;
    }

    switch (classification) {
      case "list":
        tagListBased(resource, stackTags, stage, logicalId);
        break;
      case "dict":
        tagDictBased(resource, stackTags, stage, logicalId);
        break;
      case "unclassified":
        log(`TAGGING: WARNING — unclassified resource type ${resourceType} (${logicalId}). Attempting list-based tagging. If deploy fails, add to skipTypes.`);
        tagListBased(resource, stackTags, stage, logicalId);
        break;
      case "api-only":
      case "related":
        // These are tagged post-deploy via API, not in the template
        break;
    }
  }
}

/**
 * Apply list-based tags [{Key, Value}] to a resource.
 * Merges with existing tags without overwriting.
 */
function tagListBased(resource, stackTags, stage, logicalId) {
  const newTags = buildListTags(stackTags, stage, logicalId);
  const existing = resource.Properties.Tags || [];

  // Build set of existing keys (case-insensitive)
  const existingKeys = new Set(
    existing.map((t) => (t.Key || "").toLowerCase())
  );

  // Only add tags that don't already exist
  const merged = [
    ...existing,
    ...newTags.filter((t) => !existingKeys.has(t.Key.toLowerCase())),
  ];

  resource.Properties.Tags = merged;
}

/**
 * Apply dict-based tags {key: value} to a resource.
 * Merges with existing tags without overwriting.
 */
function tagDictBased(resource, stackTags, stage, logicalId) {
  const newTags = buildDictTags(stackTags, stage, logicalId);
  const existing = resource.Properties.Tags || {};

  // Merge: existing keys take priority
  resource.Properties.Tags = { ...newTags, ...existing };
}

module.exports = { tagResources, tagListBased, tagDictBased };