Index is a helper function that performs the same operation as the index operator in the HCL expression language. That is, the result is the same as it would be for collection[key] in a configuration expression. This is exported so that applications can perform indexing in a manner consistent with
(collection, key cty.Value, srcRange *Range)
| 24 | // though nil can be provided if the calling application is going to |
| 25 | // ignore the subject of the returned diagnostics anyway. |
| 26 | func Index(collection, key cty.Value, srcRange *Range) (cty.Value, Diagnostics) { |
| 27 | const invalidIndex = "Invalid index" |
| 28 | |
| 29 | if collection.IsNull() { |
| 30 | return cty.DynamicVal, Diagnostics{ |
| 31 | { |
| 32 | Severity: DiagError, |
| 33 | Summary: "Attempt to index null value", |
| 34 | Detail: "This value is null, so it does not have any indices.", |
| 35 | Subject: srcRange, |
| 36 | }, |
| 37 | } |
| 38 | } |
| 39 | if key.IsNull() { |
| 40 | return cty.DynamicVal, Diagnostics{ |
| 41 | { |
| 42 | Severity: DiagError, |
| 43 | Summary: invalidIndex, |
| 44 | Detail: "Can't use a null value as an indexing key.", |
| 45 | Subject: srcRange, |
| 46 | }, |
| 47 | } |
| 48 | } |
| 49 | ty := collection.Type() |
| 50 | kty := key.Type() |
| 51 | if kty == cty.DynamicPseudoType || ty == cty.DynamicPseudoType { |
| 52 | return cty.DynamicVal.WithSameMarks(collection), nil |
| 53 | } |
| 54 | |
| 55 | switch { |
| 56 | |
| 57 | case ty.IsListType() || ty.IsTupleType() || ty.IsMapType(): |
| 58 | var wantType cty.Type |
| 59 | switch { |
| 60 | case ty.IsListType() || ty.IsTupleType(): |
| 61 | wantType = cty.Number |
| 62 | case ty.IsMapType(): |
| 63 | wantType = cty.String |
| 64 | default: |
| 65 | // should never happen |
| 66 | panic("don't know what key type we want") |
| 67 | } |
| 68 | |
| 69 | key, keyErr := convert.Convert(key, wantType) |
| 70 | if keyErr != nil { |
| 71 | return cty.DynamicVal, Diagnostics{ |
| 72 | { |
| 73 | Severity: DiagError, |
| 74 | Summary: invalidIndex, |
| 75 | Detail: fmt.Sprintf( |
| 76 | "The given key does not identify an element in this collection value: %s.", |
| 77 | keyErr.Error(), |
| 78 | ), |
| 79 | Subject: srcRange, |
| 80 | }, |
| 81 | } |
| 82 | } |
| 83 |