Array to map operator for #1415

pkg/yqlib/doc/operators/array-to-map.md

@@ -0,0 +1,28 @@
+# Array to Map
+
+Use this operator to convert an array to..a map. Skips over null values.
+
+Behind the scenes, this is implemented using reduce:
+
+```
+(.[] | select(. != null) ) as $i ireduce({}; .[$i | key] = $i)
+```
+
+## Simple example
+Given a sample.yml file of:
+```yaml
+cool:
+  - null
+  - null
+  - hello
+```
+then
+```bash
+yq '.cool |= array_to_map' sample.yml
+```
+will output
+```yaml
+cool:
+  2: hello
+```
+

pkg/yqlib/doc/operators/headers/array-to-map.md

@@ -0,0 +1,9 @@
+# Array to Map
+
+Use this operator to convert an array to..a map. Skips over null values.
+
+Behind the scenes, this is implemented using reduce:
+
+```
+(.[] | select(. != null) ) as $i ireduce({}; .[$i | key] = $i)
+```

pkg/yqlib/doc/usage/properties.md

@@ -149,6 +149,23 @@ person:
         - pizza
 ```
 
+## Decode properties - array should be a map
+If you have a numeric map key in your property files, use array_to_map to convert them to maps.
+
+Given a sample.properties file of:
+```properties
+things.10 = mike
+```
+then
+```bash
+yq -p=props '.things |= array_to_map' sample.properties
+```
+will output
+```yaml
+things:
+    10: mike
+```
+
 ## Roundtrip
 Given a sample.properties file of:
 ```properties

pkg/yqlib/lexer_participle.go

@@ -55,6 +55,8 @@ var participleYqRules = []*participleYqRule{
 	simpleOp("sortKeys", sortKeysOpType),
 	simpleOp("sort_?keys", sortKeysOpType),
 
+	{"ArrayToMap", "array_?to_?map", expressionOpToken(`(.[] | select(. != null) ) as $i ireduce({}; .[$i | key] = $i)`), 0},
+
 	{"YamlEncodeWithIndent", `to_?yaml\([0-9]+\)`, encodeParseIndent(YamlOutputFormat), 0},
 	{"XMLEncodeWithIndent", `to_?xml\([0-9]+\)`, encodeParseIndent(XMLOutputFormat), 0},
 	{"JSONEncodeWithIndent", `to_?json\([0-9]+\)`, encodeParseIndent(JSONOutputFormat), 0},
@@ -291,6 +293,14 @@ func opTokenWithPrefs(opType *operationType, assignOpType *operationType, prefer
 	}
 }
 
+func expressionOpToken(expression string) yqAction {
+	return func(rawToken lexer.Token) (*token, error) {
+		prefs := expressionOpPreferences{expression: expression}
+		expressionOp := &Operation{OperationType: expressionOpType, Preferences: prefs}
+		return &token{TokenType: operationToken, Operation: expressionOp}, nil
+	}
+}
+
 func flattenWithDepth() yqAction {
 	return func(rawToken lexer.Token) (*token, error) {
 		value := rawToken.Value

pkg/yqlib/lib.go

@@ -80,6 +80,8 @@ var lengthOpType = &operationType{Type: "LENGTH", NumArgs: 0, Precedence: 50, Ha
 var lineOpType = &operationType{Type: "LINE", NumArgs: 0, Precedence: 50, Handler: lineOperator}
 var columnOpType = &operationType{Type: "LINE", NumArgs: 0, Precedence: 50, Handler: columnOperator}
 
+var expressionOpType = &operationType{Type: "EXP", NumArgs: 0, Precedence: 50, Handler: expressionOperator}
+
 var collectOpType = &operationType{Type: "COLLECT", NumArgs: 1, Precedence: 50, Handler: collectOperator}
 var sliceArrayOpType = &operationType{Type: "SLICE", NumArgs: 0, Precedence: 50, Handler: sliceArrayOperator}
 var mapOpType = &operationType{Type: "MAP", NumArgs: 1, Precedence: 50, Handler: mapOperator}

pkg/yqlib/operator_array_to_map_test.go

@@ -0,0 +1,23 @@
+package yqlib
+
+import (
+	"testing"
+)
+
+var arrayToMapScenarios = []expressionScenario{
+	{
+		description: "Simple example",
+		document:    `cool: [null, null, hello]`,
+		expression:  `.cool |= array_to_map`,
+		expected: []string{
+			"D0, P[], (doc)::cool:\n    2: hello\n",
+		},
+	},
+}
+
+func TestArrayToMapScenarios(t *testing.T) {
+	for _, tt := range arrayToMapScenarios {
+		testScenario(t, &tt)
+	}
+	documentOperatorScenarios(t, "array-to-map", arrayToMapScenarios)
+}

pkg/yqlib/operator_expression.go

@@ -0,0 +1,16 @@
+package yqlib
+
+type expressionOpPreferences struct {
+	expression string
+}
+
+func expressionOperator(d *dataTreeNavigator, context Context, expressionNode *ExpressionNode) (Context, error) {
+
+	prefs := expressionNode.Operation.Preferences.(expressionOpPreferences)
+	expNode, err := ExpressionParser.ParseExpression(prefs.expression)
+	if err != nil {
+		return Context{}, err
+	}
+
+	return d.GetMatchingNodes(context, expNode)
+}

pkg/yqlib/properties_test.go

@@ -147,6 +147,14 @@ var propertyScenarios = []formatScenario{
 		expected:     expectedDecodedYaml,
 		scenarioType: "decode",
 	},
+	{
+		description:    "Decode properties - array should be a map",
+		subdescription: "If you have a numeric map key in your property files, use array_to_map to convert them to maps.",
+		input:          `things.10 = mike`,
+		expression:     `.things |= array_to_map`,
+		expected:       "things:\n  10: mike\n",
+		scenarioType:   "decode",
+	},
 	{
 		description:  "does not expand automatically",
 		skipDoc:      true,