From 61da2fc2a194c7de788d33626cf00100039f6aec Mon Sep 17 00:00:00 2001
From: Christopher Pruijsen <christopher.pruijsen@gmail.com>
Date: Thu, 10 Sep 2026 16:31:06 +0100
Subject: [PATCH] Don't strip invalid characters from ImplementationGuide name
 (#1271)

Leave sushi-config.yaml name as authored and warn when it violates the FHIR name constraint, instead of silently removing non-alphanumerics.
---
 src/ig/IGExporter.ts       | 17 +++++++++--
 test/ig/IGExporter.test.ts | 59 ++++++++++++++++++++++++++++++++++++++
 2 files changed, 74 insertions(+), 2 deletions(-)

diff --git a/src/ig/IGExporter.ts b/src/ig/IGExporter.ts
index 83462cf3c..ed66363b1 100644
--- a/src/ig/IGExporter.ts
+++ b/src/ig/IGExporter.ts
@@ -51,6 +51,8 @@ const IG_RESOURCE_FORMAT_EXTENSIONS = [
   DEPRECATED_RESOURCE_FORMAT_EXTENSION,
   CURRENT_RESOURCE_FORMAT_EXTENSION
 ];
+// FHIR ImplementationGuide.name invariant: name.matches('[A-Z]([A-Za-z0-9_]){0,254}')
+const IG_NAME_REGEX = /^[A-Z]([A-Za-z0-9_]){0,254}$/;
 
 function isR4(fhirVersion: string[]) {
   return fhirVersion.some(v => /^R4B?$/.test(getFHIRVersionInfo(v).name));
@@ -161,8 +163,7 @@ export class IGExporter {
       modifierExtension: this.config.modifierExtension,
       url: this.config.url ?? `${this.config.canonical}/ImplementationGuide/${this.config.id}`,
       version: this.config.version,
-      // name must be alphanumeric (allowing underscore as well)
-      name: this.config.name.replace(/[^A-Za-z0-9_]/g, ''),
+      name: this.config.name,
       title: this.config.title,
       status: this.config.status,
       experimental: this.config.experimental,
@@ -196,6 +197,18 @@ export class IGExporter {
         template: this.config.templates
       }
     };
+    if (this.config.name != null && !IG_NAME_REGEX.test(this.config.name)) {
+      logger.warn(
+        `The ImplementationGuide name "${this.config.name}" does not match the FHIR constraint ` +
+          "'[A-Z]([A-Za-z0-9_]){0,254}'. Valid names start with an upper-case ASCII letter ('A'..'Z') " +
+          "followed by any combination of upper- or lower-case ASCII letters ('A'..'Z', and 'a'..'z'), " +
+          "numerals ('0'-'9') and '_', with a length limit of 255 characters. " +
+          `Update the "name" property in ${this.configName}.`,
+        {
+          file: this.config.filePath
+        }
+      );
+    }
     // Add the path-history, if applicable (only applies to HL7 IGs)
     if (
       /^https?:\/\/hl7.org\//.test(this.config.canonical) &&
diff --git a/test/ig/IGExporter.test.ts b/test/ig/IGExporter.test.ts
index ba6c69557..4fce3305d 100644
--- a/test/ig/IGExporter.test.ts
+++ b/test/ig/IGExporter.test.ts
@@ -138,4 +138,63 @@ describe('IGExporter', () => {
       expect(fs.existsSync(igIniPath)).toBeFalsy();
     });
   });
+
+  describe('#ig-name', () => {
+    let tempOut: string;
+    let defs: Awaited<ReturnType<typeof getTestFHIRDefinitions>>;
+    let configPath: string;
+    let configYaml: string;
+
+    beforeAll(async () => {
+      defs = await getTestFHIRDefinitions(true, testDefsPath('r4-definitions'));
+      configPath = path.join(__dirname, '..', 'import', 'fixtures', 'minimal-config.yaml');
+      configYaml = fs.readFileSync(configPath, 'utf8');
+    });
+
+    beforeEach(() => {
+      loggerSpy.reset();
+      tempOut = temp.mkdirSync('sushi-test');
+    });
+
+    afterEach(() => {
+      temp.cleanupSync();
+    });
+
+    function exportIGWithName(name: string) {
+      const config = importConfiguration(configYaml, configPath);
+      config.name = name;
+      const pkg = new Package(config);
+      const exporter = new IGExporter(pkg, defs, __dirname);
+      exporter.export(tempOut);
+      const igPath = path.join(
+        tempOut,
+        'fsh-generated',
+        'resources',
+        'ImplementationGuide-fhir.us.minimal.json'
+      );
+      return fs.readJSONSync(igPath);
+    }
+
+    function hasNameConstraintWarning() {
+      return loggerSpy.getAllMessages('warn').some(m => m.includes('[A-Z]([A-Za-z0-9_]){0,254}'));
+    }
+
+    it('should keep an authored IG name that contains a space and warn about the FHIR name constraint', () => {
+      const igContent = exportIGWithName('Minimal IG');
+      expect(igContent.name).toBe('Minimal IG');
+      expect(hasNameConstraintWarning()).toBe(true);
+    });
+
+    it('should keep a valid IG name and not warn about the FHIR name constraint', () => {
+      const igContent = exportIGWithName('MinimalIG');
+      expect(igContent.name).toBe('MinimalIG');
+      expect(hasNameConstraintWarning()).toBe(false);
+    });
+
+    it('should keep an authored IG name with a hyphen or leading lowercase letter and warn about the FHIR name constraint', () => {
+      const igContent = exportIGWithName('example-ig');
+      expect(igContent.name).toBe('example-ig');
+      expect(hasNameConstraintWarning()).toBe(true);
+    });
+  });
 });