Add examples and specs for edge case of InlineHash

Unested symbolic or numeric keys should not be converted to strings.
These changes document that and adds specs reflecting that. Also
makes a minor change to simplify and speed perf in the InlineHash
implementation.

lib/gitlab/utils/inline_hash.rb

@@ -11,13 +11,15 @@ module Gitlab
       #
       #  {
       #    'root_param' => 'Root',
+      #    12 => 'number',
+      #    symbol: 'symbol',
       #    nested_param: {
       #      key: 'Value'
       #    },
       #    'very' => {
       #      'deep' => {
       #        'nested' => {
-      #          'param' => 'Deep nested value'
+      #          12 => 'Deep nested value'
       #        }
       #      }
       #    }
@@ -28,15 +30,17 @@ module Gitlab
       #
       #  {
       #    'root_param' => 'Root',
+      #     12 => 'number',
+      #     symbol: symbol,
       #    'nested_param.key' => 'Value',
-      #    'very.deep.nested.param' => 'Deep nested value'
+      #    'very.deep.nested.12' => 'Deep nested value'
       #  }
       #
       def merge_keys(hash, prefix: nil, connector: '.')
         result = {}
-        base_prefix = prefix ? "#{prefix}#{connector}" : ''
         pairs =
           if prefix
+            base_prefix = "#{prefix}#{connector}"
             hash.map { |key, value| ["#{base_prefix}#{key}", value] }
           else
             hash.to_a

spec/lib/gitlab/utils/inline_hash_spec.rb

@@ -6,56 +6,93 @@ describe Gitlab::Utils::InlineHash do
   describe '.merge_keys' do
     subject { described_class.merge_keys(source) }
 
-    let(:source) do
-      {
-        nested_param: {
-          key: 'Value'
-        },
-        'root_param' => 'Root',
-        'very' => {
-          'deep' => {
-            'nested' => {
-              'param' => 'Deep nested value'
+    context 'with string keys' do
+      let(:source) do
+        {
+          nested_param: {
+            key: 'Value'
+          },
+          'root_param' => 'Root',
+          'very' => {
+            'deep' => {
+              'nested' => {
+                'param' => 'Deep nested value'
+              }
             }
           }
         }
-      }
-    end
-
-    it 'transforms a nested hash into a one-level hash' do
-      is_expected.to eq(
-        'nested_param.key' => 'Value',
-        'root_param' => 'Root',
-        'very.deep.nested.param' => 'Deep nested value'
-      )
-    end
-
-    it 'retains key insertion order' do
-      expect(subject.keys)
-        .to eq(%w(nested_param.key root_param very.deep.nested.param))
-    end
-
-    context 'with a custom connector' do
-      subject { described_class.merge_keys(source, connector: '::') }
+      end
 
-      it 'uses the connector to merge keys' do
+      it 'transforms a nested hash into a one-level hash' do
         is_expected.to eq(
-          'nested_param::key' => 'Value',
+          'nested_param.key' => 'Value',
           'root_param' => 'Root',
-          'very::deep::nested::param' => 'Deep nested value'
+          'very.deep.nested.param' => 'Deep nested value'
         )
       end
+
+      it 'retains key insertion order' do
+        expect(subject.keys)
+          .to eq(%w(nested_param.key root_param very.deep.nested.param))
+      end
+
+      context 'with a custom connector' do
+        subject { described_class.merge_keys(source, connector: '::') }
+
+        it 'uses the connector to merge keys' do
+          is_expected.to eq(
+            'nested_param::key' => 'Value',
+            'root_param' => 'Root',
+            'very::deep::nested::param' => 'Deep nested value'
+          )
+        end
+      end
+
+      context 'with a starter prefix' do
+        subject { described_class.merge_keys(source, prefix: 'options') }
+
+        it 'prefixes all the keys' do
+          is_expected.to eq(
+            'options.nested_param.key' => 'Value',
+            'options.root_param' => 'Root',
+            'options.very.deep.nested.param' => 'Deep nested value'
+          )
+        end
+      end
     end
 
-    context 'with a starter prefix' do
-      subject { described_class.merge_keys(source, prefix: 'options') }
+    context 'with un-nested symbol or numeric keys' do
+      let(:unested_symbol_key_source) do
+        {
+          unnested_symbol_key: :unnested_symbol_value,
+          12 => 22,
+          nested_symbol_key: {
+            nested_symbol_key_2: :nested_symbol_value
+          }
+        }
+      end
+
+      context 'without prefix' do
+        subject { described_class.merge_keys(unested_symbol_key_source) }
 
-      it 'prefixes all the keys' do
-        is_expected.to eq(
-          'options.nested_param.key' => 'Value',
-          'options.root_param' => 'Root',
-          'options.very.deep.nested.param' => 'Deep nested value'
-        )
+        it 'converts only nested keys to inline strings' do
+          is_expected.to eq(
+            :unnested_symbol_key => :unnested_symbol_value,
+            12 => 22,
+            'nested_symbol_key.nested_symbol_key_2' => :nested_symbol_value
+          )
+        end
+      end
+
+      context 'with prefix' do
+        subject { described_class.merge_keys(unested_symbol_key_source, prefix: 'options') }
+        it 'converts prefixed keys to inline strings' do
+          is_expected.to eq(
+            'options.unnested_symbol_key' => :unnested_symbol_value,
+            'options.12' => 22,
+            'options.nested_symbol_key.nested_symbol_key_2' => :nested_symbol_value
+          )
+        end
       end
     end
   end