102 lines
3.4 KiB
Markdown
102 lines
3.4 KiB
Markdown
---
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layout: "language"
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page_title: "yamldecode - Functions - Configuration Language"
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sidebar_current: "docs-funcs-encoding-yamldecode"
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description: |-
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The yamldecode function decodes a YAML string into a representation of its
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value.
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---
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# `yamldecode` Function
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`yamldecode` parses a string as a subset of YAML, and produces a representation
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of its value.
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This function supports a subset of [YAML 1.2](https://yaml.org/spec/1.2/spec.html),
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as described below.
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This function maps YAML values to
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[Terraform language values](/docs/configuration/expressions/types.html)
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in the following way:
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| YAML type | Terraform type |
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| ------------- | ------------------------------------------------------------------ |
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| `!!str` | `string` |
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| `!!float` | `number` |
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| `!!int` | `number` |
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| `!!bool` | `bool` |
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| `!!map` | `object(...)` with attribute types determined per this table |
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| `!!seq` | `tuple(...)` with element types determined per this table |
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| `!!null` | The Terraform language `null` value |
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| `!!timestamp` | `string` in [RFC 3339](https://tools.ietf.org/html/rfc3339) format |
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| `!!binary` | `string` containing base64-encoded representation |
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The Terraform language automatic type conversion rules mean that you don't
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usually need to worry about exactly what type is produced for a given value,
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and can just use the result in an intuitive way.
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Note though that the mapping above is ambiguous -- several different source
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types map to the same target type -- and so round-tripping through `yamldecode`
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and then `yamlencode` cannot produce an identical result.
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YAML is a complex language and it supports a number of possibilities that the
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Terraform language's type system cannot represent. Therefore this YAML decoder
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supports only a subset of YAML 1.2, with restrictions including the following:
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- Although aliases to earlier anchors are supported, cyclic data structures
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(where a reference to a collection appears inside that collection) are not.
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If `yamldecode` detects such a structure then it will return an error.
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- Only the type tags shown in the above table (or equivalent alternative
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representations of those same tags) are supported. Any other tags will
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result in an error.
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- Only one YAML document is permitted. If multiple documents are present in
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the given string then this function will return an error.
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## Examples
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```
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> yamldecode("{\"hello\": \"world\"}")
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{
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"hello" = "world"
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}
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> yamldecode("true")
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true
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> yamldecode("{a: &foo [1, 2, 3], b: *foo}")
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{
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"a" = [
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1,
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2,
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3,
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]
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"b" = [
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1,
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2,
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3,
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]
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}
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> yamldecode("{a: &foo [1, *foo, 3]}")
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Error: Error in function call
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Call to function "yamldecode" failed: cannot refer to anchor "foo" from inside
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its own definition.
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> yamldecode("{a: !not-supported foo}")
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Error: Error in function call
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Call to function "yamldecode" failed: unsupported tag "!not-supported".
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```
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## Related Functions
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- [`jsondecode`](./jsondecode.html) is a similar operation using JSON instead
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of YAML.
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- [`yamlencode`](./yamlencode.html) performs the opposite operation, _encoding_
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a value as YAML.
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