fix: support schema content with pathy fileName

lib/writeSchema.js

@@ -38,7 +38,7 @@ export default function writeSchema({ schemadir, origindir }) {
       const inputPath = schema[s.fullpath] || (origindir && path.join(origindir, fileName));
       let content = schema;
 
-      if (inputPath) {
+      if (inputPath && fs.existsSync(inputPath)) {
         content = fs.readJsonSync(inputPath);
         if (schema[s.meta] && schema[s.meta].description) {
           // copy description from external file

test/api.test.js

@@ -88,6 +88,30 @@ describe('Testing Public API', () => {
     assert.strictEqual(result.markdown.length, 31);
   });
 
+  /**
+   * When running with no `outDir` and no `schemaOut`, links to JSON Schema
+   * should use `fullPath`, even if it can't be resolved.
+   */
+  it('Public API with non-existent schema path works', async () => {
+    const schemasFiles = await loadSchemas('readme-1');
+    const schemas = schemasFiles.map(({ fileName, fullPath }) => ({
+      fileName: path.join('/my-custom-path-to-schema', fileName),
+      // eslint-disable-next-line global-require, import/no-dynamic-require
+      content: fs.readJSONSync(fullPath),
+    }));
+
+    const result = jsonschema2md(schemas, {
+      // don't output anything
+      header: true,
+    });
+    assert.strictEqual(result.readme, undefined);
+    assert.strictEqual(result.schema.length, 3);
+    assert.strictEqual(result.markdown.length, 32);
+
+    assertMarkdown(result.markdown.find(({ fileName }) => fileName === 'simple.md').markdownAst)
+      .contains('[simple.schema.json](/my-custom-path-to-schema/simple.schema.json "open original schema")');
+  });
+
   it('Public API processes from single schema', async () => {
     const result = jsonschema2md(example, {
       includeReadme: true,