feat: stop regexes with whitespace (#4681)

This PR stops regexes with whitespace from being added as feature naming
patterns.

frontend/src/component/project/Project/ProjectForm/ProjectForm.tsx

@@ -210,14 +210,31 @@ const ProjectForm: React.FC<IProjectForm> = ({
     };
 
     const onSetFeatureNamingPattern = (regex: string) => {
+        const disallowedStrings = [
+            ' ',
+            '\\t',
+            '\\s',
+            '\\n',
+            '\\r',
+            '\\f',
+            '\\v',
+        ];
+        if (
+            disallowedStrings.some(blockedString =>
+                regex.includes(blockedString)
+            )
+        ) {
+            errors.featureNamingPattern =
+                'Whitespace is not allowed in the expression';
+        } else {
             try {
                 new RegExp(regex);
-            setFeatureNamingPattern && setFeatureNamingPattern(regex);
                 delete errors.featureNamingPattern;
             } catch (e) {
                 errors.featureNamingPattern = 'Invalid regular expression';
-            setFeatureNamingPattern && setFeatureNamingPattern(regex);
             }
+        }
+        setFeatureNamingPattern && setFeatureNamingPattern(regex);
         updateNamingExampleError({
             pattern: regex,
             example: featureNamingExample || '',

src/lib/features/feature-naming-pattern/feature-naming-validation.test.ts

@@ -61,6 +61,19 @@ describe('validate incoming feature naming data', () => {
         }
     });
 
+    test.each([' ', '\\t', '\\n'])(
+        'patterns with illegal characters (%s) are invalid',
+        (string) => {
+            const pattern = `-${string}[0-9]+`;
+
+            expect(
+                checkFeatureNamingData({
+                    pattern,
+                }),
+            ).toMatchObject({ state: 'invalid' });
+        },
+    );
+
     test('feature naming data with a non-empty example but an empty pattern is invalid', () => {
         expect(
             checkFeatureNamingData({
@@ -78,6 +91,19 @@ describe('validate incoming feature naming data', () => {
             }),
         ).toMatchObject({ state: 'invalid' });
     });
+
+    test('if the pattern contains disallowed characters, a match is not attempted against the example', () => {
+        const result = checkFeatureNamingData({
+            pattern: 'a. [0-9]+',
+            example: 'obviously-not-a-match',
+        });
+
+        if (result.state === 'valid') {
+            fail('Expected invalid result');
+        }
+
+        expect(result.reasons.length).toBe(1);
+    });
 });
 
 describe('validate feature flag names against a pattern', () => {

src/lib/features/feature-naming-pattern/feature-naming-validation.ts

@@ -10,23 +10,39 @@ export const checkFeatureNamingData = (
     if (featureNaming) {
         const { pattern, example, description } = featureNaming;
         const errors: string[] = [];
-        if (pattern && example && !example.match(compileRegex(pattern))) {
+        const disallowedStrings = [
+            ' ',
+            '\\t',
+            '\\s',
+            '\\n',
+            '\\r',
+            '\\f',
+            '\\v',
+        ];
+
+        if (pattern) {
+            if (disallowedStrings.some((str) => pattern.includes(str))) {
+                errors.push(
+                    `Feature flag names can not contain whitespace. You've provided a feature flag naming pattern that contains a whitespace character: "${pattern}". Remove any whitespace characters from your pattern.`,
+                );
+            } else if (example && !example.match(compileRegex(pattern))) {
                 errors.push(
                     `You've provided a feature flag naming example ("${example}") that doesn't match your feature flag naming pattern ("${pattern}"). Please provide an example that matches your supplied pattern. Bear in mind that the pattern must match the whole example, as if it were surrounded by '^' and "$".`,
                 );
             }
-
+        } else {
-        if (!pattern && example) {
+            if (example) {
                 errors.push(
                     "You've provided a feature flag naming example, but no feature flag naming pattern. You must specify a pattern to use an example.",
                 );
             }
 
-        if (!pattern && description) {
+            if (description) {
                 errors.push(
                     "You've provided a feature flag naming pattern description, but no feature flag naming pattern. You must have a pattern to use a description.",
                 );
             }
+        }
 
         const [first, ...rest] = errors;
         if (first) {