[#893] fix: Multi-line Python script result in error (#894)

Author: yottahmd

README.md

@@ -368,22 +368,27 @@ You can define positional parameters in the DAG file and override them when runn
 
 ```yaml
 # Default positional parameters
-params: input.csv output.csv 60  # Default values for $1, $2, and $3
+params: input.csv output.csv 60 # Default values for $1, $2, and $3
 
 steps:
   # Using positional parameters
-  - name: data processing
-    command: python
+  - name: Installation
+    command: pipx install pandas --include-deps
+
+  - name: Data processing
+    command: pipx run
     script: |
       import sys
       import pandas as pd
-      
+
       input_file = "$1"    # First parameter
       output_file = "$2"   # Second parameter
       timeout = "$3"       # Third parameter
-      
+
       print(f"Processing {input_file} -> {output_file} with timeout {timeout}s")
       # Add your processing logic here
+    depends:
+      - Installation
 ```
 
 Run the DAG with custom parameters:

internal/digraph/executor/command.go

@@ -108,26 +108,27 @@ func (cfg *commandConfig) newCmd(ctx context.Context, scriptFile string) (*exec.
 
 	var cmd *exec.Cmd
 	switch {
+	case cfg.Command != "" && scriptFile != "":
+		args, err := cfg.evalArgs()
+		if err != nil {
+			return nil, fmt.Errorf("failed to evaluate command args: %w", err)
+		}
+		cmd = exec.CommandContext(cfg.Ctx, cfg.Command, append(args, scriptFile)...) // nolint: gosec
+
 	case cfg.ShellCommand != "" && scriptFile != "":
 		// If script is provided ignore the shell command args
 
-		// nolint: gosec
-		cmd = exec.CommandContext(cfg.Ctx, cfg.ShellCommand, scriptFile)
+		cmd = exec.CommandContext(cfg.Ctx, cfg.ShellCommand, scriptFile) // nolint: gosec
 
 	case cfg.ShellCommand != "" && cfg.ShellCommandArgs != "":
 		// nolint: gosec
 		cmd = exec.CommandContext(cfg.Ctx, cfg.ShellCommand, "-c", cfg.ShellCommandArgs)
 
 	default:
-		args := make([]string, len(cfg.Args))
-		for i, arg := range cfg.Args {
-			arg, err := cmdutil.EvalString(cfg.Ctx, arg)
-			if err != nil {
-				return nil, fmt.Errorf("failed to evaluate command args: %w", err)
-			}
-			args[i] = arg
+		args, err := cfg.evalArgs()
+		if err != nil {
+			return nil, fmt.Errorf("failed to evaluate command args: %w", err)
 		}
-
 		cmd = createDirectCommand(cfg.Ctx, cfg.Command, args, scriptFile)
 
 	}
@@ -144,6 +145,18 @@ func (cfg *commandConfig) newCmd(ctx context.Context, scriptFile string) (*exec.
 	return cmd, nil
 }
 
+func (cfg *commandConfig) evalArgs() ([]string, error) {
+	args := make([]string, len(cfg.Args))
+	for i, arg := range cfg.Args {
+		arg, err := cmdutil.EvalString(cfg.Ctx, arg)
+		if err != nil {
+			return nil, fmt.Errorf("failed to evaluate command args: %w", err)
+		}
+		args[i] = arg
+	}
+	return args, nil
+}
+
 func init() {
 	Register("", newCommand)
 	Register("command", newCommand)

internal/integration/dag_test.go

@@ -143,6 +143,13 @@ func TestDAGExecution(t *testing.T) {
 				"OUT1": "Starting server at localhost:8080",
 			},
 		},
+		{
+			name: "Script",
+			dag:  "perl-script.yaml",
+			expectedOutputs: map[string]any{
+				"OUT1": "Hello World",
+			},
+		},
 		{
 			name: "Issue-810",
 			dag:  "issue-810.yaml",

internal/testdata/integration/perl-script.yaml

@@ -0,0 +1,8 @@
+steps:
+  - name: step1
+    command: perl
+    script: |
+      use strict;
+      use warnings;
+      print("Hello World\n");
+    output: OUT1