terraform-cdk
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cdktf: computed object key leads to broken terraform code
Expected Behavior
Given the following short example:
import {Construct} from "constructs";
import {App, Fn, TerraformStack} from "cdktf";
import {File} from "@cdktf/provider-local/lib/file";
import {LocalProvider} from "@cdktf/provider-local/lib/provider";
class MyStack extends TerraformStack {
constructor(scope: Construct, id: string) {
super(scope, id);
new LocalProvider(this, "localprovider")
new File(this, "ruwentest", {
filename: "ruwentest.json",
content: Fn.jsonencode({
[Fn.join("", ["foo", "bar"])]: "baz"
}
)
})
}
}
I would expect to have a json file
{"foobar":"baz"}
since the Fn.join function should join foo and bar together.
The relevant line in the cdk json should look like this:
"content": "${jsonencode({join(\"\", [\"foo\", \"bar\"]) = \"baz\"})}",
Actual Behavior
When I run cdktf synth, it is successful. But the generated json looks like this:
{
"resource": {
"local_file": {
"ruwentest": {
"//": {
"metadata": {
"path": "cdktf/ruwentest",
"uniqueId": "ruwentest"
}
},
"content": "${jsonencode({\"join(\"\", [\"foo\", \"bar\"])\" = undefined})}",
"filename": "ruwentest.json"
}
}
}
}
When I run it with --hcl, it is also broken, but slightly worse:
resource "local_file" "ruwentest" {
content = "${jsonencode({ "join(" ", [" foo ", " bar "])" = undefined })}"
filename = "ruwentest.json"
}
Steps to Reproduce
- Create a new typescript project.
- Make sure you got the local provider installed.
- Make this the main.ts
import {Construct} from "constructs";
import {App, Fn, TerraformStack} from "cdktf";
import {File} from "@cdktf/provider-local/lib/file";
import {LocalProvider} from "@cdktf/provider-local/lib/provider";
class MyStack extends TerraformStack {
constructor(scope: Construct, id: string) {
super(scope, id);
new LocalProvider(this, "localprovider")
new File(this, "ruwentest", {
filename: "ruwentest.json",
content: Fn.jsonencode({
[Fn.join("", ["foo", "bar"])]: "baz"
}
)
})
}
}
const app = new App();
new MyStack(app, "cdktf");
app.synth();
Versions
language: typescript cdktf-cli: 0.20.4 node: v18.15.0 cdktf: 0.20.4 constructs: 10.3.0 jsii: null terraform: 1.7.2 arch: x64 os: linux 6.1.0-17-amd64 providers @cdktf/provider-aws (PREBUILT) terraform provider version: 5.33.0 prebuilt provider version: 19.2.0 cdktf version: ^0.20.0 @cdktf/provider-kubernetes (PREBUILT) terraform provider version: 2.25.2 prebuilt provider version: 11.0.0 cdktf version: ^0.20.0 @cdktf/provider-local (PREBUILT) terraform provider version: 2.4.1 prebuilt provider version: 10.0.0 cdktf version: ^0.20.0
Providers
┌───────────────┬──────────────────┬─────────┬────────────┬────────────────────────────┬─────────────────┐ │ Provider Name │ Provider Version │ CDKTF │ Constraint │ Package Name │ Package Version │ ├───────────────┼──────────────────┼─────────┼────────────┼────────────────────────────┼─────────────────┤ │ aws │ 5.33.0 │ ^0.20.0 │ │ @cdktf/provider-aws │ 19.2.0 │ ├───────────────┼──────────────────┼─────────┼────────────┼────────────────────────────┼─────────────────┤ │ kubernetes │ 2.25.2 │ ^0.20.0 │ │ @cdktf/provider-kubernetes │ 11.0.0 │ ├───────────────┼──────────────────┼─────────┼────────────┼────────────────────────────┼─────────────────┤ │ local │ 2.4.1 │ ^0.20.0 │ │ @cdktf/provider-local │ 10.0.0 │ └───────────────┴──────────────────┴─────────┴────────────┴────────────────────────────┴─────────────────┘
Gist
No response
Possible Solutions
No response
Workarounds
No response
Anything Else?
No response
References
No response
Help Wanted
- [ ] I'm interested in contributing a fix myself
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I would expect to have a json file
{"foobar":"baz"}
That expectation is off, by using Fn.join
you are invoking the terraform function join
that you can see rendered in your output. If you want foobar
you need to use the programming language join, so e.g. ["foo", "bar"].join("")
.
Argh I realised I actually didn't past the error message :man_facepalming:
Let me put the steps again:
- On the above typescript code, run
terraform synth
-
cd cdktf.out/stacks/cdktf
-
cat cdk.tf.json { "//": { "metadata": { "backend": "local", "stackName": "cdktf", "version": "0.20.4" }, "outputs": { } }, "provider": { "local": [ { } ] }, "resource": { "local_file": { "ruwentest": { "//": { "metadata": { "path": "cdktf/ruwentest", "uniqueId": "ruwentest" } }, "content": "${jsonencode({\"join(\"\", [\"foo\", \"bar\"])\" = undefined})}", "filename": "ruwentest.json" } } }, "terraform": { "backend": { "local": { "path": "xxx/cdktf/terraform.cdktf.tfstate" } }, "required_providers": { "local": { "source": "hashicorp/local", "version": "2.4.1" } } } }
(See the undefined there?) -
terraform apply ╷ │ Error: Missing key/value separator │ │ on cdk.tf.json line 26, in resource.local_file.ruwentest: │ 26: "content": "${jsonencode({\"join(\"\", [\"foo\", \"bar\"])\" = undefined})}", │ │ Expected an equals sign ("=") to mark the beginning of the attribute value. ╵
Let me add a bit of context:
I am using cdktf as a glorified terraform code generator. I just generate the code and then use the generated terraform json in my various environments.
As part of that I am generating IAM policies from various outputs of other resources.
In general the join works. If I use Fn.join to generate the value side of a json object, it works. Just not on the keyside.
new File(this, "ruwentest", {
filename: "ruwentest.json",
content: Fn.jsonencode({
"baz": [Fn.join("", ["foo", "bar"])]
}
)
})
works as expected