Merge pull request #43 from gocardless/does-it-exist

Add `.exists?`

CHANGELOG.md

@@ -1,3 +1,8 @@
+v0.4.0
+------
+- Add an `.exists?` method that returns `true`/`false` depending on whether a given
+  key exists or not.
+
 v0.3.0
 ------
 - Add support for S3

lib/bucket_store/key_storage.rb

@@ -143,6 +143,19 @@ def delete!
       true
     end
 
+    # Checks if the given key exists.
+    #
+    # This will only return true when the `key` exactly matches an object within the bucket
+    # and conversely it will return false when `key` matches an internal path to an object.
+    # For example if the bucket has a key named `prefix/file.txt`, it will only return
+    # `true` when `exists?` is called on `prefix/file.txt`. Any other combination
+    # (`prefix/`, `prefix/file`) will instead return `false`.
+    #
+    # @return [bool] `true` if the given key exists, `false` if not
+    def exists?
+      list.first == "#{adapter_type}://#{bucket}/#{key}"
+    end
+
     private
 
     attr_reader :adapter

lib/bucket_store/version.rb

@@ -1,5 +1,5 @@
 # frozen_string_literal: true
 
 module BucketStore
-  VERSION = "0.3.0"
+  VERSION = "0.4.0"
 end

spec/bucket_store/key_storage_spec.rb

@@ -117,7 +117,7 @@ def build_for(key)
     end
   end
 
-  describe "delete!" do
+  describe "#delete!" do
     before do
       build_for("inmemory://bucket/file1").upload!("content1")
     end
@@ -126,4 +126,32 @@ def build_for(key)
       expect(build_for("inmemory://bucket/file1").delete!).to eq(true)
     end
   end
+
+  describe "#exists?" do
+    before do
+      build_for("inmemory://bucket/file").upload!("content1")
+      build_for("inmemory://bucket/prefix/another_file").upload!("content2")
+    end
+
+    it "returns false when a key does not exist" do
+      expect(build_for("inmemory://bucket/invalid").exists?).to be false
+      expect(build_for("inmemory://invalid_bucket/file").exists?).to be false
+    end
+
+    it "returns true when a key exists" do
+      expect(build_for("inmemory://bucket/file").exists?).to be true
+      expect(build_for("inmemory://bucket/prefix/another_file").exists?).to be true
+    end
+
+    it "returns false when a key matches a path" do
+      expect(build_for("inmemory://bucket").exists?).to be false
+      expect(build_for("inmemory://bucket/").exists?).to be false
+      expect(build_for("inmemory://bucket/prefix/").exists?).to be false
+    end
+
+    it "returns false when a key only partially matches a file name" do
+      expect(build_for("inmemory://bucket/f").exists?).to be false
+      expect(build_for("inmemory://bucket/prefix/a").exists?).to be false
+    end
+  end
 end