Changed makeLegalName optionally return a valid python identifier.

Author: lizlooney

src/blocks/mrc_class_method_def.ts

@@ -302,7 +302,7 @@ const CLASS_METHOD_DEF = {
           }
         });
 
-    const legalName = makeLegalName(name, otherNames, /* mustBeginWithLetter */ true);
+    const legalName = makeLegalName(name, otherNames, /* mustBeValidPythonIdentifier */ true);
     const oldName = nameField.getValue();
     if (oldName && oldName !== name && oldName !== legalName) {
       // Rename any callers.

src/blocks/mrc_component.ts

@@ -177,7 +177,7 @@ const COMPONENT = {
           otherNames.push(block.getFieldValue(FIELD_NAME));
         });
 
-    const legalName = makeLegalName(name, otherNames, /* mustBeginWithLetter */ true);
+    const legalName = makeLegalName(name, otherNames, /* mustBeValidPythonIdentifier */ true);
     const oldName = nameField.getValue();
     if (oldName && oldName !== name && oldName !== legalName) {
       // Rename any callers.

src/blocks/mrc_event.ts

@@ -198,7 +198,7 @@ const EVENT = {
           otherNames.push(block.getFieldValue(FIELD_EVENT_NAME));
         });
 
-    const legalName = makeLegalName(name, otherNames, /* mustBeginWithLetter */ false);
+    const legalName = makeLegalName(name, otherNames, /* mustBeValidPythonIdentifier */ false);
     const oldName = nameField.getValue();
     if (oldName && oldName !== name && oldName !== legalName) {
       // Rename any callers.

src/blocks/mrc_mechanism.ts

@@ -180,7 +180,7 @@ const MECHANISM = {
           otherNames.push(block.getFieldValue(FIELD_NAME));
         });
 
-    const legalName = makeLegalName(name, otherNames, /* mustBeginWithLetter */ true);
+    const legalName = makeLegalName(name, otherNames, /* mustBeValidPythonIdentifier */ true);
     const oldName = nameField.getValue();
     if (oldName && oldName !== name && oldName !== legalName) {
       // Rename any callers.

src/blocks/utils/validator.ts

@@ -24,9 +24,9 @@
  * A legal name is:
  * 1. not empty.
  * 2. doesn't collide with other names.
- * 3. Optional: begins with a letter.
+ * 3. Optional: is a valid python identifier.
  */
-export function makeLegalName(proposedName: string, otherNames: string[], mustBeginWithLetter: boolean): string {
+export function makeLegalName(proposedName: string, otherNames: string[], mustBeValidPythonIdentifier: boolean): string {
   const otherNamesLowerCase = otherNames.map(n => n.toLowerCase());
 
   // Strip leading and trailing whitespace.
@@ -35,10 +35,27 @@ export function makeLegalName(proposedName: string, otherNames: string[], mustBe
   // Make the name non-empty.
   name = name || 'unnamed';
 
-  if (mustBeginWithLetter) {
-    // If the name begins with a non-alphabetic character, insert the letter a at the beginning.
-    if (!name.match(/^[a-zA-Z].*$/)) {
-      name = 'a' + name;
+  if (mustBeValidPythonIdentifier) {
+    if (!name.match(/^[a-zA-Z_][a-zA-Z0-9_]*$/)) {
+      let identifier = '';
+      const firstChar = name[0];
+      if (/[a-zA-Z_]/.test(firstChar)) {
+        identifier += firstChar;
+      } else if (/[a-zA-Z0-9_]/.test(firstChar)) {
+        // If the first character would be valid as the second charactor, insert an underscore.
+        identifier += '_' + firstChar;
+      } else {
+        identifier += '_';
+      }
+      for (let i = 1; i < name.length; i++) {
+        const char = name[i];
+        if (/[a-zA-Z0-9_]/.test(char)) {
+          identifier += char;
+        } else {
+          identifier += '_';
+        }
+      }
+      name = identifier;
     }
   }