Check write errors

README.md

@@ -82,6 +82,7 @@ yq() {
 - [List matching paths of a given path expression](https://mikefarah.gitbook.io/yq/commands/read#path-only)
 - Update a yaml file given a [path expression](https://mikefarah.gitbook.io/yq/commands/write-update#basic) or [script file](https://mikefarah.gitbook.io/yq/commands/write-update#basic)
 - Update creates any missing entries in the path on the fly
+- Deeply compare yaml files
 - Keeps yaml formatting and comments when updating
 - [Validate a yaml file](https://mikefarah.gitbook.io/yq/commands/validate)
 - Create a yaml file given a [deep path and value](https://mikefarah.gitbook.io/yq/commands/create#creating-a-simple-yaml-file) or a [script file](https://mikefarah.gitbook.io/yq/commands/create#creating-using-a-create-script)

cmd/compare.go

@@ -14,11 +14,13 @@ func createCompareCmd() *cobra.Command {
 	var cmdCompare = &cobra.Command{
 		Use:     "compare [yaml_file_a] [yaml_file_b]",
 		Aliases: []string{"x"},
-		Short:   "yq x data1.yml data2.yml ",
+		Short:   "yq x [--prettyPrint/-P] dataA.yaml dataB.yaml 'b.e(name==fr*).value'",
 		Example: `
 yq x - data2.yml # reads from stdin
+yq x -pp dataA.yaml dataB.yaml '**' # compare paths
+yq x -d1 dataA.yaml dataB.yaml 'a.b.c'
 `,
-		Long: "Compares two yaml files, prints the difference. same ",
+		Long: "Deeply compares two yaml files, prints the difference. Use with prettyPrint flag to ignore formatting differences.",
 		RunE: compareDocuments,
 	}
 	cmdCompare.PersistentFlags().StringVarP(&docIndex, "doc", "d", "0", "process document index number (0 based, * for all documents)")
@@ -44,17 +46,17 @@ func compareDocuments(cmd *cobra.Command, args []string) error {
 
 	var matchingNodesA []*yqlib.NodeContext
 	var matchingNodesB []*yqlib.NodeContext
-	var errorReadingStream error
+	var errorDoingThings error
 
-	matchingNodesA, errorReadingStream = readYamlFile(args[0], path, updateAll, docIndexInt)
+	matchingNodesA, errorDoingThings = readYamlFile(args[0], path, updateAll, docIndexInt)
 
-	if errorReadingStream != nil {
-		return errorReadingStream
+	if errorDoingThings != nil {
+		return errorDoingThings
 	}
 
-	matchingNodesB, errorReadingStream = readYamlFile(args[1], path, updateAll, docIndexInt)
-	if errorReadingStream != nil {
-		return errorReadingStream
+	matchingNodesB, errorDoingThings = readYamlFile(args[1], path, updateAll, docIndexInt)
+	if errorDoingThings != nil {
+		return errorDoingThings
 	}
 
 	if prettyPrint {
@@ -64,8 +66,14 @@ func compareDocuments(cmd *cobra.Command, args []string) error {
 
 	var dataBufferA bytes.Buffer
 	var dataBufferB bytes.Buffer
-	printResults(matchingNodesA, bufio.NewWriter(&dataBufferA))
-	printResults(matchingNodesB, bufio.NewWriter(&dataBufferB))
+	errorDoingThings = printResults(matchingNodesA, bufio.NewWriter(&dataBufferA))
+	if errorDoingThings != nil {
+		return errorDoingThings
+	}
+	errorDoingThings = printResults(matchingNodesB, bufio.NewWriter(&dataBufferB))
+	if errorDoingThings != nil {
+		return errorDoingThings
+	}
 
 	cmd.Print(diff.Diff(dataBufferA.String(), dataBufferB.String()))
 	return nil

cmd/utils.go

@@ -67,8 +67,8 @@ func appendDocument(originalMatchingNodes []*yqlib.NodeContext, dataBucket yaml.
 
 func printValue(node *yaml.Node, writer io.Writer) error {
 	if node.Kind == yaml.ScalarNode {
-		writer.Write([]byte(node.Value))
-		return nil
+		_, errorWriting := writer.Write([]byte(node.Value))
+		return errorWriting
 	}
 	return printNode(node, writer)
 }
@@ -97,6 +97,11 @@ func updateStyleOfNode(node *yaml.Node, style yaml.Style) {
 	}
 }
 
+func writeString(writer io.Writer, txt string) error {
+	_, errorWriting := writer.Write([]byte(txt))
+	return errorWriting
+}
+
 func printResults(matchingNodes []*yqlib.NodeContext, writer io.Writer) error {
 	bufferedWriter := bufio.NewWriter(writer)
 	defer safelyFlush(bufferedWriter)
@@ -104,17 +109,23 @@ func printResults(matchingNodes []*yqlib.NodeContext, writer io.Writer) error {
 	if len(matchingNodes) == 0 {
 		log.Debug("no matching results, nothing to print")
 		if defaultValue != "" {
-			bufferedWriter.Write([]byte(defaultValue))
+			return writeString(bufferedWriter, defaultValue)
 		}
 		return nil
 	}
-
+	var errorWriting error
 	for index, mappedDoc := range matchingNodes {
 		switch printMode {
 		case "p":
-			bufferedWriter.Write([]byte(lib.PathStackToString(mappedDoc.PathStack)))
+			errorWriting = writeString(bufferedWriter, lib.PathStackToString(mappedDoc.PathStack))
+			if errorWriting != nil {
+				return errorWriting
+			}
 			if index < len(matchingNodes)-1 {
-				bufferedWriter.Write([]byte("\n"))
+				errorWriting = writeString(bufferedWriter, "\n")
+				if errorWriting != nil {
+					return errorWriting
+				}
 			}
 		case "pv", "vp":
 			// put it into a node and print that.
@@ -132,7 +143,10 @@ func printResults(matchingNodes []*yqlib.NodeContext, writer io.Writer) error {
 			// Printing our Scalars does not print a new line at the end
 			// we only want to do that if there are more values (so users can easily script extraction of values in the yaml)
 			if index < len(matchingNodes)-1 && mappedDoc.Node.Kind == yaml.ScalarNode {
-				bufferedWriter.Write([]byte("\n"))
+				errorWriting = writeString(bufferedWriter, "\n")
+				if errorWriting != nil {
+					return errorWriting
+				}
 			}
 		}
 	}