Fix issue #20 "unexpected end of JSON input" error

.github/workflows/build.yml

@@ -2,34 +2,89 @@ name: Build
 
 on:
   push:
-    branches: [ main ]
+    branches: [main]
   pull_request:
-    branches: [ main ]
+    branches: [main]
 
 jobs:
-
   build:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v4
+      - uses: actions/checkout@v4
+
+      - name: Run Gosec Security Scanner
+        uses: securego/gosec@master
+        with:
+          args: -exclude=G204 ./...
+
+      - name: Set up Go
+        uses: actions/setup-go@v4
+        with:
+          go-version: "1.21"
+
+      - name: golangci-lint
+        uses: golangci/golangci-lint-action@v3
+        with:
+          version: latest
+
+      - name: Test
+        run: go test -v ./...
+
+      - name: Build
+        run: go build
+
+  demo:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+
+      - name: Set up Go
+        uses: actions/setup-go@v4
+        with:
+          go-version: "1.21"
+
+      - name: Build
+        run: |
+          go build -o example/tf-summarize
+
+      - name: Setup Terraform
+        uses: hashicorp/setup-terraform@v2
+        with:
+          terraform_wrapper: false
+
+      - name: Print tf-summarize version and help
+        run: |
+          ./tf-summarize -v
+          ./tf-summarize -h
+        working-directory: ./example
+
+      - name: Terraform Init
+        run: terraform init
+        working-directory: ./example
+
+      - name: Terraform Plan
+        run: |
+          terraform plan -out=tfplan -refresh=false # -refresh=false is only for demo workflow
+          terraform show -json tfplan > tfplan.json
+        working-directory: ./example
 
-    - name: Run Gosec Security Scanner
-      uses: securego/gosec@master
-      with:
-        args: -exclude=G204 ./...
+      - name: summary in table format
+        run: terraform show -json tfplan | ./tf-summarize
+        working-directory: ./example
 
-    - name: Set up Go
-      uses: actions/setup-go@v4
-      with:
-        go-version: '1.21'
+      - name: summary in table format with plan JSON file passed
+        run: |
+          ./tf-summarize tfplan.json
+        working-directory: ./example
 
-    - name: golangci-lint
-      uses: golangci/golangci-lint-action@v3
-      with:
-        version: latest
+      - name: summary in tree format
+        run: terraform show -json tfplan | ./tf-summarize -tree
+        working-directory: ./example
 
-    - name: Test
-      run: go test -v ./...
+      - name: summary in separate tree format
+        run: terraform show -json tfplan | ./tf-summarize -separate-tree
+        working-directory: ./example
 
-    - name: Build
-      run: go build
+      - name: summary in draw visual tree format
+        run: terraform show -json tfplan | ./tf-summarize -tree -draw
+        working-directory: ./example

main.go

@@ -37,7 +37,7 @@ func main() {
 	err := validateFlags(*tree, *separateTree, *drawable, *md, args)
 	logIfErrorAndExit("invalid input flags: %s\n", err, flag.Usage)
 
-	newReader, err := reader.CreateReader(os.Stdin, args)
+	newReader, err := reader.CreateReader(args)
 	logIfErrorAndExit("error creating input reader: %s\n", err, flag.Usage)
 
 	input, err := newReader.Read()

reader/reader.go

@@ -2,9 +2,10 @@ package reader
 
 import (
 	"bufio"
+	"errors"
 	"fmt"
 	"io"
-	"os"
+	"strings"
 )
 
 type Reader interface {
@@ -22,19 +23,22 @@ func readFile(f io.Reader) ([]byte, error) {
 		input = append(input, line...)
 	}
 	if err != io.EOF {
-		return nil, fmt.Errorf("error reading file: %s", err.Error())
+		return nil, fmt.Errorf("error reading input: %s", err.Error())
+	}
+	if len(input) == 0 {
+		return nil, errors.New("no input data; expected input via a non-empty file or via STDIN")
 	}
 	return input, nil
 }
 
-func CreateReader(stdin *os.File, args []string) (Reader, error) {
-	stat, _ := stdin.Stat()
-	if (stat.Mode() & os.ModeCharDevice) == 0 {
-		return NewStdinReader(), nil
+func CreateReader(args []string) (Reader, error) {
+	if len(args) > 1 {
+		return nil, fmt.Errorf("expected input via a single filename argument or via STDIN; received multiple arguments: %s", strings.Join(args, ", "))
 	}
-	if len(args) < 1 {
-		return nil, fmt.Errorf("should have either stdin input through pipe or first argument should be file")
+
+	if len(args) == 1 {
+		return NewFileReader(args[0]), nil
 	}
-	fileName := args[0]
-	return NewFileReader(fileName), nil
+
+	return NewStdinReader(), nil
 }