fix(CLI): restore empty-file download when a tag filter matches nothing

.github/workflows/test-cli.yml

@@ -26,15 +26,20 @@ jobs:
         uses: actions/setup-go@v2
         with:
           go-version: '1.24.4'
-      - name: Generate CLI and run unit tests
+      - name: Generate CLI
         env:
           GOPRIVATE: github.com/phrase/phrase-go
         run: |
-          npm install
-          npm run generate.go
+          {
+            npm install
+            npm run generate.go
+            cd ./clients/cli
+            go mod edit -replace github.com/phrase/phrase-go/v4=../go
+            npm run generate.cli
+          } > generate.log 2>&1 || { cat generate.log; exit 1; }
+      - name: Build and run unit tests
+        run: |
           cd ./clients/cli
-          go mod edit -replace github.com/phrase/phrase-go/v4=../go
-          npm run generate.cli
           go build .
           go test -v ./...
       - name: Install Ruby and rspec
@@ -46,7 +51,7 @@ jobs:
       - name: Run integration tests
         run: |
           cd ./clients/cli
-          bundle exec rspec
+          bundle exec rspec --format documentation
       - name: License check
         uses: phrase/actions/lawa-ci@v1
         with:

clients/cli/cmd/internal/pull.go

@@ -273,16 +273,16 @@ func (target *Target) PullParallel(client *phrase.APIClient, cache *DownloadCach
 				return dlErr
 			}
 
-			if cache != nil {
-				updateCache(cache, cacheKey, response)
-			}
-
 			if err := copyToDestination(file, lf.Path); err != nil {
 				err = fmt.Errorf("%s for %s", err, lf.Path)
 				results[i] = downloadResult{errMsg: err.Error()}
 				return err
 			}
 
+			if cache != nil {
+				updateCache(cache, cacheKey, response)
+			}
+
 			results[i] = downloadResult{
 				message: lf.Message(),
 				path:    lf.RelPath(),
@@ -445,23 +445,32 @@ func (target *Target) downloadSynchronously(client *phrase.APIClient, localeFile
 		}
 	}
 
+	if err := copyToDestination(file, localeFile.Path); err != nil {
+		return err
+	}
+
 	if cache != nil {
 		updateCache(cache, cacheKey, response)
 	}
 
-	return copyToDestination(file, localeFile.Path)
+	return nil
 }
 
 func copyToDestination(file *os.File, path string) error {
-	if file == nil {
-		return fmt.Errorf("no content to write to %s", path)
-	}
-	defer file.Close()
 	destFile, err := os.Create(path)
 	if err != nil {
 		return err
 	}
 	defer destFile.Close()
+
+	// The API returns a 200 with an empty body when a filter (e.g. --tags)
+	// matches no translations; decode() then leaves file nil with no error.
+	// That's a valid empty export, not a failed download, so write an empty
+	// file rather than treating it as an error.
+	if file == nil {
+		return nil
+	}
+	defer file.Close()
 	_, err = io.Copy(destFile, file)
 	return err
 }

clients/cli/cmd/internal/pull_parallel_test.go

@@ -1,6 +1,8 @@
 package internal
 
 import (
+	"os"
+	"path/filepath"
 	"testing"
 )
 
@@ -44,3 +46,67 @@ func TestBuildDownloadOpts_TagHandling(t *testing.T) {
 		t.Errorf("expected tag to be empty string, got %q", opts.Tag.Value())
 	}
 }
+
+// A nil *os.File represents a 200 response with an empty body, which the API
+// returns when a filter (e.g. --tags) matches no translations. copyToDestination
+// must write an empty file for this case rather than failing, since it's a valid
+// (if unusual) export result, not a failed download.
+func TestCopyToDestination_NilFileWritesEmptyFile(t *testing.T) {
+	path := filepath.Join(t.TempDir(), "en.json")
+
+	if err := copyToDestination(nil, path); err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+
+	data, err := os.ReadFile(path)
+	if err != nil {
+		t.Fatalf("expected file to be created at %s: %v", path, err)
+	}
+	if len(data) != 0 {
+		t.Errorf("expected empty file, got %q", data)
+	}
+}
+
+func TestCopyToDestination_NilFileTruncatesExistingContent(t *testing.T) {
+	path := filepath.Join(t.TempDir(), "en.json")
+	if err := os.WriteFile(path, []byte(`{"hello":"world"}`), 0o644); err != nil {
+		t.Fatalf("failed to seed existing file: %v", err)
+	}
+
+	if err := copyToDestination(nil, path); err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+
+	data, err := os.ReadFile(path)
+	if err != nil {
+		t.Fatalf("failed to read file: %v", err)
+	}
+	if len(data) != 0 {
+		t.Errorf("expected previously downloaded content to be replaced with empty file, got %q", data)
+	}
+}
+
+func TestCopyToDestination_CopiesFileContent(t *testing.T) {
+	srcPath := filepath.Join(t.TempDir(), "src.json")
+	if err := os.WriteFile(srcPath, []byte(`{"hello":"world"}`), 0o644); err != nil {
+		t.Fatalf("failed to write source file: %v", err)
+	}
+	src, err := os.Open(srcPath)
+	if err != nil {
+		t.Fatalf("failed to open source file: %v", err)
+	}
+	defer src.Close()
+
+	destPath := filepath.Join(t.TempDir(), "dest.json")
+	if err := copyToDestination(src, destPath); err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+
+	data, err := os.ReadFile(destPath)
+	if err != nil {
+		t.Fatalf("failed to read dest file: %v", err)
+	}
+	if string(data) != `{"hello":"world"}` {
+		t.Errorf("expected copied content, got %q", data)
+	}
+}

clients/cli/spec/pull_spec.rb

@@ -248,6 +248,62 @@
     end
   end
 
+  describe "pull with tag filter matching no translations" do
+    let(:config) do
+      <<~YAML
+        phrase:
+          host: #{ENV.fetch("BASE_URL")}
+          project_id: "#{project_id}"
+          access_token: "#{token}"
+          pull:
+            targets:
+            - file: "#{@tmpdir}/locales/<locale_code>.yml"
+              params:
+                file_format: yml
+                tags: "nonexistent-tag"
+      YAML
+    end
+
+    before do
+      # The API responds with 200 and an empty body when a tag filter
+      # matches zero translations - this is not an error.
+      mock_set!("GET", "/projects/#{project_id}/locales/#{locale_en_id}/download",
+        status: 200,
+        body: "",
+        headers: { "content-type" => "application/x-yaml" }
+      )
+      mock_set!("GET", "/projects/#{project_id}/locales/#{locale_de_id}/download",
+        status: 200,
+        body: "",
+        headers: { "content-type" => "application/x-yaml" }
+      )
+    end
+
+    it "succeeds and writes an empty file instead of failing" do
+      r = run_cli("pull", config: config)
+
+      expect(r[:exit_code]).to eq(0)
+
+      en_file_path = File.join(@tmpdir, "locales", "en.yml")
+      de_file_path = File.join(@tmpdir, "locales", "de.yml")
+
+      expect(File.exist?(en_file_path)).to be true
+      expect(File.exist?(de_file_path)).to be true
+      expect(File.read(en_file_path)).to eq("")
+      expect(File.read(de_file_path)).to eq("")
+    end
+
+    it "succeeds with --parallel too" do
+      r = run_cli("pull", "--parallel", config: config)
+
+      expect(r[:exit_code]).to eq(0)
+
+      en_file_path = File.join(@tmpdir, "locales", "en.yml")
+      expect(File.exist?(en_file_path)).to be true
+      expect(File.read(en_file_path)).to eq("")
+    end
+  end
+
   describe "pull with locale_mapping" do
     let(:config) do
       <<~YAML