Fixes #3875

Author: zachleat

src/Data/TemplateData.js

@@ -658,7 +658,8 @@ class TemplateData {
 			}
 
 			// Deduplicate tags
-			return [...new Set(tags)];
+			// Coerce to string #3875
+			return [...new Set(tags)].map((entry) => String(entry));
 		}
 
 		return tags;

test/Issue3875Test.js

@@ -0,0 +1,82 @@
+import test from "ava";
+import Eleventy from "../src/Eleventy.js";
+
+test("#3875 numeric tags", async (t) => {
+  let elev = new Eleventy("test/noop", false, {
+    config(eleventyConfig) {
+      eleventyConfig.addFilter("keys", (obj) => Object.keys(obj));
+      eleventyConfig.addTemplate("index.njk", "{{ collections | keys }}", {
+        tags: [1,2,3]
+      });
+    }
+  });
+
+  let results = await elev.toJSON();
+  t.is(results[0].content, "1,2,3,all");
+});
+
+test("#3875 numeric tags (via front matter)", async (t) => {
+  let elev = new Eleventy("test/noop", false, {
+    config(eleventyConfig) {
+      eleventyConfig.addFilter("keys", (obj) => Object.keys(obj));
+      eleventyConfig.addTemplate("index.njk", `---
+tags:
+  - 1
+  - 2
+  - 3
+---
+{{ collections | keys }}`);
+    }
+  });
+
+  let results = await elev.toJSON();
+  t.is(results[0].content, "1,2,3,all");
+});
+
+test("#3875 consume a numeric tag collection (njk)", async (t) => {
+  let elev = new Eleventy("test/noop", false, {
+    config(eleventyConfig) {
+      eleventyConfig.addFilter("keyTypes", (obj) => Object.keys(obj).map(entry => typeof entry).join(","));
+      eleventyConfig.addTemplate("child.njk", "", {
+        tags: [1]
+      });
+      eleventyConfig.addTemplate("index.njk", `{{ collections | keyTypes }}:{{ collections[1].length }}:{{ collections['1'].length }}`);
+    }
+  });
+
+  let results = await elev.toJSON();
+  t.is(results.filter(entry => entry.inputPath.endsWith("index.njk"))[0].content, "string,string:1:1");
+});
+
+test("#3875 consume a numeric tag collection (liquid)", async (t) => {
+  let elev = new Eleventy("test/noop", false, {
+    config(eleventyConfig) {
+      eleventyConfig.addFilter("keyTypes", (obj) => Object.keys(obj).map(entry => typeof entry).join(","));
+      eleventyConfig.addTemplate("child.njk", "", {
+        tags: [1]
+      });
+      eleventyConfig.addTemplate("index.liquid", `{{ collections | keyTypes }}:{{ collections[1].length }}:{{ collections['1'].length }}`);
+    }
+  });
+
+  let results = await elev.toJSON();
+  t.is(results.filter(entry => entry.inputPath.endsWith("index.liquid"))[0].content, "string,string:1:1");
+});
+
+test("#3875 consume a numeric tag collection (11ty.js)", async (t) => {
+  let elev = new Eleventy("test/noop", false, {
+    config(eleventyConfig) {
+      eleventyConfig.addTemplate("child.njk", "", {
+        tags: [1]
+      });
+      eleventyConfig.addTemplate("index.11ty.js", {
+        render(data) {
+          return `${Object.keys(data.collections).map(entry => typeof entry).join(",")}:${data.collections[1].length}:${data.collections['1'].length}`
+        }
+      });
+    }
+  });
+
+  let results = await elev.toJSON();
+  t.is(results.filter(entry => entry.inputPath.endsWith("index.11ty.js"))[0].content, "string,string:1:1");
+});