fix(flags): reject leading-zero semver values in local evaluation (#150)

Author: dmarticus

.changeset/strict-semver-leading-zeros.md

@@ -0,0 +1,5 @@
+---
+'posthog-ruby': patch
+---
+
+Reject semver values with leading zeros (e.g. `1.07.3`, `01.02.03`) during local feature flag evaluation, per semver 2.0.0 §2. Both override values and flag values are validated; invalid inputs raise `InconclusiveMatchError` so the condition does not match.

lib/posthog/feature_flags.rb

@@ -456,6 +456,16 @@ def self.relative_date_parse_for_feature_flag_matching(value)
       parsed_dt
     end
 
+    # Parse a single semver numeric identifier, rejecting empty, non-digit, or
+    # leading-zero values per semver 2.0.0 §2.
+    def self.parse_semver_numeric(part)
+      raise InconclusiveMatchError, 'Invalid semver format' if part.nil? || part.empty? || part !~ /^\d+$/
+      # Semver 2.0.0 §2: numeric identifiers MUST NOT include leading zeros.
+      raise InconclusiveMatchError, 'Invalid semver format' if part.length > 1 && part[0] == '0'
+
+      part.to_i
+    end
+
     # Parse a semver string into a comparable [major, minor, patch] integer array.
     # Handles v-prefix, whitespace, pre-release suffixes. Defaults missing components to 0.
     def self.parse_semver(value)
@@ -471,14 +481,9 @@ def self.parse_semver(value)
 
       raise InconclusiveMatchError, 'Invalid semver format' if parts.empty? || parts[0].to_s.empty?
 
-      # Check for leading dot or non-numeric parts
-      parts.each do |part|
-        raise InconclusiveMatchError, 'Invalid semver format' if part.empty? || part !~ /^\d+$/
-      end
-
-      major = parts[0].to_i
-      minor = parts.length > 1 ? parts[1].to_i : 0
-      patch = parts.length > 2 ? parts[2].to_i : 0
+      major = parse_semver_numeric(parts[0])
+      minor = parts.length > 1 ? parse_semver_numeric(parts[1]) : 0
+      patch = parts.length > 2 ? parse_semver_numeric(parts[2]) : 0
 
       [major, minor, patch]
     end
@@ -535,20 +540,22 @@ def self.semver_wildcard_bounds(value)
 
       raise InconclusiveMatchError, 'Invalid semver wildcard format' if parts.empty?
 
-      parts.each do |part|
-        raise InconclusiveMatchError, 'Invalid semver wildcard format' if part !~ /^\d+$/
+      numeric = parts.map do |part|
+        parse_semver_numeric(part)
+      rescue InconclusiveMatchError
+        raise InconclusiveMatchError, 'Invalid semver wildcard format'
       end
 
-      major = parts[0].to_i
-      case parts.length
+      major = numeric[0]
+      case numeric.length
       when 1
         [[major, 0, 0], [major + 1, 0, 0]]
       when 2
-        minor = parts[1].to_i
+        minor = numeric[1]
         [[major, minor, 0], [major, minor + 1, 0]]
       else
-        minor = parts[1].to_i
-        patch = parts[2].to_i
+        minor = numeric[1]
+        patch = numeric[2]
         [[major, minor, patch], [major, minor, patch + 1]]
       end
     end

spec/posthog/feature_flag_spec.rb

@@ -1888,10 +1888,47 @@ module PostHog
       expect(FeatureFlagsPoller.match_property(property2, { 'version' => '1.2.3' })).to be true
     end
 
-    it 'with semver operators and leading zeros' do
+    it 'with semver operators rejects override values with leading zeros' do
       property = { 'key' => 'version', 'value' => '1.2.3', 'operator' => 'semver_eq' }
-      expect(FeatureFlagsPoller.match_property(property, { 'version' => '01.02.03' })).to be true
-      expect(FeatureFlagsPoller.match_property(property, { 'version' => '001.002.003' })).to be true
+
+      ['01.2.3', '1.02.3', '1.2.03', '1.07.3', '001.2.3', '01.02.03', '001.002.003'].each do |bad|
+        expect do
+          FeatureFlagsPoller.match_property(property, { 'version' => bad })
+        end.to raise_error(InconclusiveMatchError), "expected #{bad.inspect} to be rejected"
+      end
+    end
+
+    it 'with semver operators rejects flag values with leading zeros' do
+      gt = { 'key' => 'version', 'value' => '1.07.3', 'operator' => 'semver_gt' }
+      expect do
+        FeatureFlagsPoller.match_property(gt, { 'version' => '2.0.0' })
+      end.to raise_error(InconclusiveMatchError)
+
+      caret = { 'key' => 'version', 'value' => '01.2.3', 'operator' => 'semver_caret' }
+      expect do
+        FeatureFlagsPoller.match_property(caret, { 'version' => '1.2.3' })
+      end.to raise_error(InconclusiveMatchError)
+
+      tilde = { 'key' => 'version', 'value' => '1.02.3', 'operator' => 'semver_tilde' }
+      expect do
+        FeatureFlagsPoller.match_property(tilde, { 'version' => '1.2.3' })
+      end.to raise_error(InconclusiveMatchError)
+
+      wildcard = { 'key' => 'version', 'value' => '01.*', 'operator' => 'semver_wildcard' }
+      expect do
+        FeatureFlagsPoller.match_property(wildcard, { 'version' => '1.2.3' })
+      end.to raise_error(InconclusiveMatchError)
+    end
+
+    it 'with semver operators accepts literal zero components' do
+      eq_zero = { 'key' => 'version', 'value' => '0.1.0', 'operator' => 'semver_eq' }
+      expect(FeatureFlagsPoller.match_property(eq_zero, { 'version' => '0.1.0' })).to be true
+
+      eq_zero_zero = { 'key' => 'version', 'value' => '0.0.0', 'operator' => 'semver_eq' }
+      expect(FeatureFlagsPoller.match_property(eq_zero_zero, { 'version' => '0.0.0' })).to be true
+
+      eq_major_zero = { 'key' => 'version', 'value' => '1.0.0', 'operator' => 'semver_eq' }
+      expect(FeatureFlagsPoller.match_property(eq_major_zero, { 'version' => '1.0.0' })).to be true
     end
 
     it 'with semver operators and partial versions' do