fix: write to GITHUB_OUTPUT file

Author: chuhlomin

.github/workflows/main.yml

@@ -28,7 +28,6 @@ jobs:
           images: ${{ env.DOCKER_IMAGE }}
           tags: latest
 
-
       - name: Build and push
         uses: docker/build-push-action@v2
         with:
@@ -39,3 +38,14 @@ jobs:
             ${{ steps.meta.outputs.tags }}
             ${{ env.DOCKER_IMAGE }}:${{ github.sha }}
           labels: ${{ steps.meta.outputs.labels }}
+
+      - name: Test action
+        uses: ./ # Uses an action in the root directory
+        id: render
+        with:
+          template: ./testdata/template.txt
+          vars: |
+            name: world
+
+      - name: Get `result` output
+        run: echo "${{ steps.render.outputs.result }}"

main.go

@@ -7,7 +7,6 @@ import (
 	"io/ioutil"
 	"os"
 	"reflect"
-	"strings"
 	"text/template"
 
 	"github.com/caarlos0/env/v6"
@@ -56,18 +55,10 @@ func run() error {
 		return fmt.Errorf("failed to render template: %v", err)
 	}
 
-	githubOutput := fmt.Sprintf("%s=%s", "result", escape(output))
-	if os.Getenv("GITHUB_OUTPUT") != "" {
-		githubOutput = fmt.Sprintln(os.Getenv("GITHUB_OUTPUT")) + githubOutput
-	}
-
-	err = os.Setenv("GITHUB_OUTPUT", githubOutput)
-	if err != nil {
-		return fmt.Errorf("failed to set GITHUB_OUTPUT: %v", err)
+	if err = writeOutput(output); err != nil {
+		return err
 	}
 
-	fmt.Printf("::debug::%s", os.Getenv("GITHUB_OUTPUT"))
-
 	if len(c.ResultPath) != 0 {
 		err := ioutil.WriteFile(c.ResultPath, []byte(output), 0644)
 		if err != nil {
@@ -126,16 +117,36 @@ func renderTemplate(templateFilePath string, vars vars) (string, error) {
 	return result.String(), nil
 }
 
-func escape(str string) string {
-	/*
-		set-output truncates multiline strings.
-		% and \n and \r can be escaped, the runner will unescape in reverse:
-		https://github.community/t/set-output-truncates-multiline-strings/16852
-	*/
-
-	return strings.NewReplacer(
-		"%", "%25",
-		"\n", "%0A",
-		"\r", "%0D",
-	).Replace(str)
+func writeOutput(output string) error {
+	githubOutput := formatOutput("result", output)
+	if githubOutput == "" {
+		return nil
+	}
+
+	path := os.Getenv("GITHUB_OUTPUT")
+
+	f, err := os.OpenFile(path, os.O_APPEND|os.O_WRONLY, 0644)
+	if err != nil {
+		return fmt.Errorf("failed to open result file %q: %v", path, err)
+	}
+	defer f.Close()
+
+	if _, err = f.WriteString(githubOutput); err != nil {
+		return fmt.Errorf("failed to write result to file %q: %v", path, err)
+	}
+
+	return nil
+}
+
+func formatOutput(name, value string) string {
+	if value == "" {
+		return ""
+	}
+
+	// if value contains new line, use multiline format
+	if bytes.ContainsRune([]byte(value), '\n') {
+		return fmt.Sprintf("%s<<OUTPUT\n%s\nOUTPUT", name, value)
+	}
+
+	return fmt.Sprintf("%s=%s", name, value)
 }

main_test.go

@@ -7,22 +7,23 @@ import (
 	"testing"
 )
 
-func TestEscape(t *testing.T) {
+func TestFormatOutput(t *testing.T) {
 	tests := []struct {
 		in       string
 		expected string
 	}{
 		{"", ""},
-		{"text", "text"},
-		{"%", "%25"},
-		{"\n", "%0A"},
-		{"\r", "%0D"},
+		{"text", "result=text"},
+		{"%", "result=%"},
+		{"some\ntext", "result<<OUTPUT\nsome\ntext\nOUTPUT"},
+		{"\n", "result<<OUTPUT\n\n\nOUTPUT"},
+		{"\r", "result=\r"},
 	}
 
 	for _, tt := range tests {
-		actual := escape(tt.in)
+		actual := formatOutput("result", tt.in)
 		if actual != tt.expected {
-			t.Errorf("escape(%q) was incorrect, got: %q, want: %q.", tt.in, actual, tt.expected)
+			t.Errorf("formatOutput(%q) was incorrect, got: %q, want: %q.", tt.in, actual, tt.expected)
 		}
 	}
 }