feat(lib): Make default property in Fn.lookup optional and introduce Fn.lookupNested

examples/csharp/documentation/FunctionsOther.cs

@@ -0,0 +1,65 @@
+// Copyright (c) HashiCorp, Inc.
+// SPDX-License-Identifier: MPL-2.0
+
+
+using System;
+using System.IO;
+using System.Collections.Generic;
+using System.Linq;
+using Constructs;
+using HashiCorp.Cdktf;
+using aws.Provider;
+using aws.DataAwsAvailabilityZones;
+
+namespace Examples
+{
+    class FunctionsOtherStack : TerraformStack
+    {
+        public FunctionsOtherStack(Construct scope, string name) : base(scope, name)
+        {
+            new AwsProvider(this, "aws", new AwsProviderConfig
+            {
+                Region = "eu-central-1"
+            });
+
+
+            // DOCS_BLOCK_START:functions-raw
+            DataAwsAvailabilityZones zones = new DataAwsAvailabilityZones(this, "zones", new DataAwsAvailabilityZonesConfig
+            {
+                State = "available"
+            });
+
+            new TerraformOutput(this, "half-of-the-zone", new TerraformOutputConfig
+            {
+                Value = $"${{length({zones.Fqn}.names) / 2}}"
+            });
+            // DOCS_BLOCK_END:functions-raw
+
+            // DOCS_BLOCK_START:functions-lookup
+            TerraformVariable v = new TerraformVariable(this, "complex_object", new TerraformVariableConfig
+            {
+                Type = "object({users: list(object({name: string}))})",
+            });
+            new TerraformOutput(this, "users", new TerraformOutputConfig
+            {
+                Value = Fn.Lookup(v.Value, "users")
+            });
+            new TerraformOutput(this, "first-user-name", new TerraformOutputConfig
+            {
+                Value = Fn.LookupNested(v.Value, new[] { "users", "0", "name" })
+            });
+            // DOCS_BLOCK_END:functions-lookup
+
+            // DOCS_BLOCK_START:functions-raw-string
+            new TerraformOutput(this, "quotes", new TerraformOutputConfig
+            {
+                Value = Fn.RawString("\"b\"")
+            });
+            new TerraformOutput(this, "template", new TerraformOutputConfig
+            {
+                Value = Fn.RawString("${TEMPLATE}")
+            });
+            // DOCS_BLOCK_END:functions-raw-string
+        }
+    }
+}

examples/csharp/documentation/Main.cs

@@ -68,7 +68,7 @@ public static void Main(string[] args)
             new Examples.Producer(app, "cdktf-producer");
             new Examples.Consumer(app, "cdktf-consumer");
             new Examples.OperatorsStack(app, "operators");
-            new Examples.FunctionsRawStack(app, "functions-raw");
+            new Examples.FunctionsOtherStack(app, "functions-other");
 
             TerraformStack stack = new TerraformStack(app, "stack-escape-hatches");
             // DOCS_BLOCK_START:stack-escape-hatches

examples/go/documentation/functions-other.go

@@ -0,0 +1,37 @@
+// Copyright (c) HashiCorp, Inc.
+// SPDX-License-Identifier: MPL-2.0
+
+package main
+
+import (
+	"github.com/aws/constructs-go/constructs/v10"
+	"github.com/aws/jsii-runtime-go"
+	"github.com/hashicorp/terraform-cdk-go/cdktf"
+)
+
+func NewFunctionsOtherStack(scope constructs.Construct, name string) cdktf.TerraformStack {
+	stack := cdktf.NewTerraformStack(scope, &name)
+
+	// DOCS_BLOCK_START:functions-lookup
+	v := cdktf.NewTerraformVariable(stack, jsii.String("complex-object"), &cdktf.TerraformVariableConfig{
+		Type: jsii.String("object({users: list(object({name: string}))})"),
+	})
+	cdktf.NewTerraformOutput(stack, jsii.String("users"), &cdktf.TerraformOutputConfig{
+		Value: cdktf.Fn_Lookup(v.Value(), jsii.String("users"), nil),
+	})
+	cdktf.NewTerraformOutput(stack, jsii.String("first-user-name"), &cdktf.TerraformOutputConfig{
+		Value: cdktf.Fn_LookupNested(v.Value(), &[]interface{}{"users", 0, "name"}),
+	})
+	// DOCS_BLOCK_END:functions-lookup
+
+	// DOCS_BLOCK_START:functions-raw-string
+	cdktf.NewTerraformOutput(stack, jsii.String("quotes"), &cdktf.TerraformOutputConfig{
+		Value: cdktf.Fn_RawString(jsii.String("\"b\"")),
+	})
+	cdktf.NewTerraformOutput(stack, jsii.String("template"), &cdktf.TerraformOutputConfig{
+		Value: cdktf.Fn_RawString(jsii.String("${TEMPLATE}")),
+	})
+	// DOCS_BLOCK_END:functions-raw-string
+
+	return stack
+}

examples/go/documentation/main.go

@@ -15,6 +15,7 @@ func main() {
 	NewAspectsStack(app, "aspects")
 	NewPrefixAspectsStack(app, "aspects-validation")
 	NewFunctionsStack(app, "functions")
+	NewFunctionsOtherStack(app, "functions-other")
 	NewOperatorsAndFunctionsRawStack(app, "operators-functions-raw")
 	NewHclInteropStack(app, "hcl-interop")
 	NewProvidersStack(app, "providers")

examples/java/documentation/src/main/java/com/mycompany/app/MainFunction.java

@@ -11,8 +11,12 @@
 
 import software.constructs.Construct;
 
+import java.util.Arrays;
+
 // DOCS_BLOCK_START:functions-usage-example
 import com.hashicorp.cdktf.Fn;
+import com.hashicorp.cdktf.TerraformVariable;
+import com.hashicorp.cdktf.TerraformVariableConfig;
 import com.hashicorp.cdktf.TerraformOutput;
 import com.hashicorp.cdktf.TerraformOutputConfig;
 import imports.aws.data_aws_availability_zones.DataAwsAvailabilityZones;
@@ -41,5 +45,26 @@ public MainFunction(Construct scope, String id) {
                 .build());
         // DOCS_BLOCK_END:functions-usage-example
 
+        // DOCS_BLOCK_START:functions-lookup
+        TerraformVariable v = new TerraformVariable(this, "complex_object", TerraformVariableConfig.builder()
+                .type("object({users: list(object({name: string}))})")
+                .build());
+        new TerraformOutput(this, "users", TerraformOutputConfig.builder()
+                .value(Fn.lookup(v.getValue(), "users"))
+                .build());
+        new TerraformOutput(this, "first-user-name", TerraformOutputConfig.builder()
+                .value(Fn.lookupNested(v.getValue(), Arrays.asList("users", "0", "name")))
+                .build());
+        // DOCS_BLOCK_END:functions-lookup
+
+        // DOCS_BLOCK_START:functions-raw-string
+        new TerraformOutput(this, "quotes", TerraformOutputConfig.builder()
+                .value(Fn.rawString("\"b\""))
+                .build());
+        new TerraformOutput(this, "template", TerraformOutputConfig.builder()
+                .value(Fn.rawString("${TEMPLATE}"))
+                .build());
+        // DOCS_BLOCK_END:functions-raw-string
+
     }
 }

examples/python/documentation/functions.py

@@ -2,7 +2,7 @@
 # SPDX-License-Identifier: MPL-2.0
 
 from constructs import Construct
-from cdktf import TerraformStack, App
+from cdktf import TerraformStack, App, TerraformVariable, Token
 # DOCS_BLOCK_START:functions-usage-example
 from cdktf import Fn, TerraformOutput
 from imports.aws.provider import AwsProvider
@@ -28,3 +28,26 @@ def __init__(self, scope: Construct, id: str):
 
         # DOCS_BLOCK_END:functions-usage-example
 
+        # INTERNAL NOTE: Due to an JSII bug, we have to pass a default value for lookup in Python
+        # We can remove it, once https://github.com/aws/jsii/pull/4209 is released
+        # DOCS_BLOCK_START:functions-lookup
+        v = TerraformVariable(self, "complex-object",
+            type = 'object({users: list(object({name: string}))})',
+        )
+        TerraformOutput(self, 'users',
+            value=Fn.lookup(v.value, "users", "default")
+        )
+        TerraformOutput(self, 'first_user_name',
+            value=Fn.lookup_nested(v.value, ["users", 0, "name"])
+        )
+        # DOCS_BLOCK_END:functions-lookup
+
+        # DOCS_BLOCK_START:functions-raw-string
+        TerraformOutput(self, 'quotes',
+            value=Fn.raw_string('"b"')
+        )
+        TerraformOutput(self, 'template',
+            value=Fn.raw_string('${TEMPLATE}')
+        )
+        # DOCS_BLOCK_END:functions-raw-string
+

examples/typescript/documentation/functions.ts

@@ -1,7 +1,7 @@
 // Copyright (c) HashiCorp, Inc
 // SPDX-License-Identifier: MPL-2.0
 // DOCS_BLOCK_START:functions
-import { TerraformStack } from "cdktf";
+import { TerraformStack, TerraformVariable } from "cdktf";
 import { Construct } from "constructs";
 import { AwsProvider } from "@cdktf/provider-aws/lib/aws-provider";
 // DOCS_BLOCK_END:functions
@@ -37,6 +37,25 @@ export class FunctionsStack extends TerraformStack {
     });
     // DOCS_BLOCK_END:functions
 
+    // DOCS_BLOCK_START:functions-lookup
+    const v = new TerraformVariable(this, "complex_object", {
+      type: "object({users: list(object({name: string}))})",
+    });
+    new TerraformOutput(this, "users", { value: Fn.lookup(v.value, "users") });
+    new TerraformOutput(this, "first_user_name", {
+      value: Fn.lookupNested(v.value, ["users", 0, "name"]),
+    });
+    // DOCS_BLOCK_END:functions-lookup
+
+    // DOCS_BLOCK_START:functions-raw-string
+    new TerraformOutput(this, "quotes", {
+      value: Fn.rawString(`"b"`),
+    });
+    new TerraformOutput(this, "template", {
+      value: Fn.rawString("${TEMPLATE}"),
+    });
+    // DOCS_BLOCK_END:functions-raw-string
+
     // DOCS_BLOCK_START:operators
 
     // ...

packages/cdktf/lib/terraform-functions.ts

@@ -1,6 +1,7 @@
 // Copyright (c) HashiCorp, Inc
 // SPDX-License-Identifier: MPL-2.0
-import { rawString, Token } from ".";
+import { propertyAccess, rawString, Token } from ".";
+import { asAny } from "./functions/helpers";
 import { FnGenerated } from "./functions/terraform-functions.generated";
 
 // eslint-disable-next-line jsdoc/require-jsdoc
@@ -21,12 +22,22 @@ export class Fn extends FnGenerated {
    * {@link /terraform/docs/language/functions/lookup.html lookup} retrieves the value of a single element from a map, given its key. If the given key does not exist, the given default value is returned instead.
    * @param {any} inputMap
    * @param {string} key
-   * @param {Array<any>} defaultValue
+   * @param {any} [defaultValue]
    */
-  static lookup(inputMap: any, key: string, defaultValue: any) {
+  static lookup(inputMap: any, key: string, defaultValue?: any) {
     // overwritten because lookup() uses a variadic argument for its optional defaultValue
-    // we don't model it as optional since not passing it is deprecated in favor of the native Terraform expression "inputMap[key]"
-    return Fn._lookup(inputMap, key, [defaultValue]);
+    if (defaultValue) return Fn._lookup(inputMap, key, [defaultValue]);
+    return asAny(propertyAccess(inputMap, [key])); // -> renders inputMap[key] (which is recommended if no default value is given)
+  }
+
+  /**
+   * returns a property access expression that accesses the property at the given path in the given inputMap.
+   * For example lookupNested(x, ["a", "b", "c"]) will return a Terraform expression like x["a"]["b"]["c"]
+   * @param {any} inputMap
+   * @param {Array<any>} path
+   */
+  static lookupNested(inputMap: any, path: any[]) {
+    return asAny(propertyAccess(inputMap, path));
   }
 
   /**

packages/cdktf/test/fqn.test.ts

@@ -106,7 +106,7 @@ test("works when escape is mid-way", () => {
     name: "${test_resource.first-resource}-second",
     tags: {
       firstResourceName:
-        'simple-test-${lookup(test_resource.other-resource, "name", "")}-${test_resource.first-resource.name}',
+        "simple-test-${test_resource.other-resource.name}-${test_resource.first-resource.name}",
     },
   };
 
@@ -147,7 +147,7 @@ test("after escape, reverts to normal", () => {
     name: "${test_resource.first-resource}-second",
     tags: {
       firstResourceName:
-        'simple-test-${test_resource.first-resource.name}-${lookup(test_resource.other-resource, "name", "")}',
+        "simple-test-${test_resource.first-resource.name}-${test_resource.other-resource.name}",
     },
   };
 
@@ -186,7 +186,7 @@ test("can have multiple escapes", () => {
     name: "${test_resource.first-resource}-second",
     tags: {
       firstResourceName:
-        'simple-test-${test_resource.first-resource.name}-${lookup(test_resource.other-resource, "name", "")}',
+        "simple-test-${test_resource.first-resource.name}-${test_resource.other-resource.name}",
     },
   };
 
@@ -291,7 +291,7 @@ test("works with functions", () => {
     name: "${test_resource.first-resource}-second",
     tags: {
       firstResourceName:
-        'simple-test-${test_resource.first-resource.name}-${lookup(test_resource.other-resource, "name", "")}',
+        "simple-test-${test_resource.first-resource.name}-${test_resource.other-resource.name}",
     },
   };
 
@@ -416,7 +416,7 @@ test("allows functions within functions", () => {
     name: "bar",
     tags: {
       firstResourceName:
-        '${lookup(test_resource.other-resource, "name", upper(lookup(test_resource.other-resource, "name", "")))}',
+        '${lookup(test_resource.other-resource, "name", upper(test_resource.other-resource.name))}',
     },
   };
 

packages/cdktf/test/functions.test.ts

@@ -553,3 +553,43 @@ it("errors mentioning function name and argument", () => {
     `"Argument 1 of replace failed the validation: Error: 'this one " not' can not be used as value directly since it has unescaped double quotes in it. To safely use the value please use Fn.rawString on your string."`
   );
 });
+
+test("Property access using lookup and lookupNested functions", () => {
+  const app = Testing.app();
+  const stack = new TerraformStack(app, "test");
+
+  const variable = new TerraformVariable(stack, "test-var", {
+    type: `object({a = object({b = string}), z = string})`,
+  });
+
+  new TerraformOutput(stack, "lookup", {
+    value: Fn.lookup(variable.value, "z", "defaultzzzz"),
+  });
+  new TerraformOutput(stack, "native-access", {
+    value: Fn.lookup(variable.value, "z"),
+  });
+  new TerraformOutput(stack, "native-access-nested", {
+    value: Fn.lookupNested(variable.value, ["a", "b"]),
+  });
+
+  expect(Testing.synth(stack)).toMatchInlineSnapshot(`
+    "{
+      "output": {
+        "lookup": {
+          "value": "\${lookup(var.test-var, \\"z\\", \\"defaultzzzz\\")}"
+        },
+        "native-access": {
+          "value": "\${var.test-var.z}"
+        },
+        "native-access-nested": {
+          "value": "\${var.test-var.a.b}"
+        }
+      },
+      "variable": {
+        "test-var": {
+          "type": "object({a = object({b = string}), z = string})"
+        }
+      }
+    }"
+  `);
+});