Can load expressions from file #1120

acceptance_tests/basic.sh

@@ -3,6 +3,7 @@
 setUp() {
   rm test*.yml 2>/dev/null || true
   rm .xyz 2>/dev/null || true
+  rm instructions.txt 2>/dev/null || true
 }
 
 testBasicEvalRoundTrip() {
@@ -26,7 +27,17 @@ testBasicExpressionMatchesFileName() {
 
   X=$(./yq ea --expression '.xyz' test.yml)
   assertEquals "123" "$X"
+}
+
+testBasicExpressionFromFile() {
+  ./yq -n ".xyz = 123" > test.yml
+  echo '.xyz = "meow" | .cool = "frog"' > instructions.txt
+
+  X=$(./yq --from-file instructions.txt test.yml -o=j -I=0)
+  assertEquals '{"xyz":"meow","cool":"frog"}' "$X"
 
+  X=$(./yq ea --from-file instructions.txt test.yml -o=j -I=0)
+  assertEquals '{"xyz":"meow","cool":"frog"}' "$X"
 }
 
 testBasicGitHubAction() {

cmd/constant.go

@@ -30,3 +30,5 @@ var splitFileExp = ""
 var completedSuccessfully = false
 
 var forceExpression = ""
+
+var expressionFile = ""

cmd/evaluate_all_command.go

@@ -126,7 +126,10 @@ func evaluateAll(cmd *cobra.Command, args []string) (cmdError error) {
 
 	allAtOnceEvaluator := yqlib.NewAllAtOnceEvaluator()
 
-	expression, args := processArgs(pipingStdIn, args)
+	expression, args, err := processArgs(pipingStdIn, args)
+	if err != nil {
+		return err
+	}
 	yqlib.GetLogger().Debugf("processed args: %v", args)
 
 	switch len(args) {

cmd/evalute_sequence_command.go

@@ -143,7 +143,10 @@ func evaluateSequence(cmd *cobra.Command, args []string) (cmdError error) {
 		}
 		defer frontMatterHandler.CleanUp()
 	}
-	expression, args := processArgs(pipingStdIn, args)
+	expression, args, err := processArgs(pipingStdIn, args)
+	if err != nil {
+		return err
+	}
 
 	switch len(args) {
 	case 0:

cmd/root.go

@@ -86,6 +86,8 @@ yq -i '.stuff = "foo"' myfile.yml # update myfile.yml inplace
 
 	rootCmd.PersistentFlags().StringVarP(&splitFileExp, "split-exp", "s", "", "print each result (or doc) into a file named (exp). [exp] argument must return a string. You can use $index in the expression as the result counter.")
 
+	rootCmd.PersistentFlags().StringVarP(&expressionFile, "from-file", "", "", "Load expression from specified file.")
+
 	rootCmd.AddCommand(
 		createEvaluateSequenceCommand(),
 		createEvaluateAllCommand(),

cmd/utils.go

@@ -137,14 +137,22 @@ func processStdInArgs(pipingStdin bool, args []string) []string {
 	return append(args, "-")
 }
 
-func processArgs(pipingStdin bool, originalArgs []string) (string, []string) {
+func processArgs(pipingStdin bool, originalArgs []string) (string, []string, error) {
+	expression := forceExpression
+	if expressionFile != "" {
+		expressionBytes, err := os.ReadFile(expressionFile)
+		if err != nil {
+			return "", nil, err
+		}
+		expression = string(expressionBytes)
+	}
+
 	args := processStdInArgs(pipingStdin, originalArgs)
 	yqlib.GetLogger().Debugf("processed args: %v", args)
-	expression := forceExpression
 	if expression == "" && len(args) > 0 && args[0] != "-" && !maybeFile(args[0]) {
 		yqlib.GetLogger().Debug("assuming expression is '%v'", args[0])
 		expression = args[0]
 		args = args[1:]
 	}
-	return expression, args
+	return expression, args, nil
 }