internal/lsp: Provide (opt-in) custom semantic tokens & modifier

docs/language-clients.md

@@ -16,6 +16,10 @@ Clients specifically should **not** send `*.tf.json`, `*.tfvars.json` nor
 Packer HCL config nor any other HCL config files as the server is not
 equipped to handle these file types.
 
+## Syntax Highlighting
+
+Read more about how we recommend Terraform files to be highlighted in [syntax-highlighting.md](./syntax-highlighting.md).
+
 ### Internal parser
 
 The server expects clients to use standard text synchronization LSP methods

docs/syntax-highlighting.md

@@ -0,0 +1,80 @@
+# Syntax Highlighting
+
+Highlighting syntax is one of the key features expected of any editor. Editors typically have a few different solutions to choose from. Below is our view on how we expect editors to highlight Terraform code while using this language server.
+
+## Static Grammar
+
+Highlighting Terraform language syntax via static grammar (such as TextMate) _accurately_ may be challenging but brings more immediate value to the end user, since starting language server may take time. Also not all language clients may implement semantic token based highlighting.
+
+HashiCorp maintains a set of grammars in https://github.com/hashicorp/syntax and we encourage you to use the available Terraform grammar as the *primary* way of highlighting the Terraform language.
+
+## Semantic Tokens
+
+[LSP (Language Server Protocol) 3.16](https://microsoft.github.io/language-server-protocol/specifications/specification-3-16/) introduced language server-driven highlighting. This language server is better equipped to provide more contextual and accurate highlighting as it can parse the whole AST, unlike a TextMate grammar operating on a regex-basis.
+
+LSP 3.17 does support use cases where semantic highlighting is the only way to highlight a file (through [`augmentsSyntaxTokens` client capability](https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#semanticTokensClientCapabilities)). However in the context of the Terraform language we recommend semantic highlighting to be used as in *addition* to a static grammar - i.e. this server does _not_ support `augmentsSyntaxTokens: false` mode and is not expected to be used in isolation to highlight configuration.
+
+There are two main use cases we're targeting with semantic tokens.
+
+### Improving Accuracy
+
+Regex-based grammars (like TextMate) operate on line-basis, which makes it difficult to accurately highlight certain parts of the syntax, for example nested blocks occuring in the Terraform language (as below).
+
+```hcl
+terraform {
+	required_providers {
+
+	}
+}
+```
+
+Language server can use the AST and other important context (such as Terraform version or provider schema) to fully understand the whole configuration and provide more accurate highlighting.
+
+### Custom Theme Support
+
+Many _default_ IDE themes are intended as general-purpose themes, highlighting token types, modifiers and scopes mappable to most languages. We recognize that theme authors would benefit from token types & modifiers which more accurately reflect the Terraform language.
+
+LSP spec doesn't _explicitly_ encourage defining custom token types or modifiers, however the default token types and modifiers which are part of the spec are not well suited to express all the different constructs of a DSL (Domain Specific Language), such as Terraform language. With that in mind we use the LSP client/server capability negotiation mechanism to provide the following custom token types & modifiers with fallback to the predefined ones.
+
+#### Token Types
+
+Primary token types are preferred if deemed supported by client per `SemanticTokensClientCapabilities.TokenTypes`, fallbacks are also only reported if client claim support (using the same capability).
+
+Fallback types are chosen based on meaningful semantic mapping and default themes in VSCode.
+
+| Primary | Fallback |
+| ------- | -------- |
+| `hcl-blockType` | `type` |
+| `hcl-blockLabel` | `enumMember` |
+| `hcl-attrName` | `property` |
+| `hcl-bool` | `keyword` |
+| `hcl-number` | `number` |
+| `hcl-string` | `string` |
+| `hcl-objectKey` | `parameter` |
+| `hcl-mapKey` | `parameter` |
+| `hcl-keyword` | `variable` |
+| `hcl-traversalStep` | `variable` |
+| `hcl-typeCapsule` | `function` |
+| `hcl-typePrimitive` | `keyword` |
+
+#### Token Modifiers
+
+Modifiers which do not have fallback are not reported at all if not received within `SemanticTokensClientCapabilities.TokenModifiers` (just like fallback modifier that isn't supported).
+
+| Primary | Fallback |
+| ------- | -------- |
+| `hcl-dependent` | `defaultLibrary` |
+| `terraform-data` |  |
+| `terraform-locals` |  |
+| `terraform-module` |  |
+| `terraform-output` |  |
+| `terraform-provider` |  |
+| `terraform-resource` |  |
+| `terraform-provisioner` |  |
+| `terraform-connection` |  |
+| `terraform-variable` |  |
+| `terraform-terraform` |  |
+| `terraform-backend` |  |
+| `terraform-name` |  |
+| `terraform-type` |  |
+| `terraform-requiredProviders` |  |

go.mod

@@ -14,12 +14,12 @@ require (
 	github.com/hashicorp/go-uuid v1.0.2
 	github.com/hashicorp/go-version v1.4.0
 	github.com/hashicorp/hc-install v0.3.1
-	github.com/hashicorp/hcl-lang v0.0.0-20220314150337-d770b425fb22
+	github.com/hashicorp/hcl-lang v0.0.0-20220316204834-49ffde67ce68
 	github.com/hashicorp/hcl/v2 v2.11.1
 	github.com/hashicorp/terraform-exec v0.16.0
 	github.com/hashicorp/terraform-json v0.13.0
 	github.com/hashicorp/terraform-registry-address v0.0.0-20210816115301-cb2034eba045
-	github.com/hashicorp/terraform-schema v0.0.0-20220225085753-faadc57bd40a
+	github.com/hashicorp/terraform-schema v0.0.0-20220316204916-c6585b866d6d
 	github.com/kylelemons/godebug v1.1.0 // indirect
 	github.com/mh-cbon/go-fmt-fail v0.0.0-20160815164508-67765b3fbcb5
 	github.com/mitchellh/cli v1.1.2

go.sum

@@ -295,10 +295,8 @@ github.com/hashicorp/hc-install v0.3.1 h1:VIjllE6KyAI1A244G8kTaHXy+TL5/XYzvrtFi8
 github.com/hashicorp/hc-install v0.3.1/go.mod h1:3LCdWcCDS1gaHC9mhHCGbkYfoY6vdsKohGjugbZdZak=
 github.com/hashicorp/hcl v1.0.0 h1:0Anlzjpi4vEasTeNFn2mLJgTSwt0+6sfsiTG8qcWGx4=
 github.com/hashicorp/hcl v1.0.0/go.mod h1:E5yfLk+7swimpb2L/Alb/PJmXilQ/rhwaUYs4T20WEQ=
-github.com/hashicorp/hcl-lang v0.0.0-20211118124824-da3a292c5d7a/go.mod h1:0W3+VP07azoS+fCX5hWk1KxwHnqf1s9J7oBg2cFXm1c=
-github.com/hashicorp/hcl-lang v0.0.0-20220314150337-d770b425fb22 h1:u++Zu5hfJPSNuHh7cV1QfTItINnEGRMdOvT9KjaDQUQ=
-github.com/hashicorp/hcl-lang v0.0.0-20220314150337-d770b425fb22/go.mod h1:vyszbX6YNHCKIaVUhbh3LIZljxwYOtgWCIkhT5zKfjc=
-github.com/hashicorp/hcl/v2 v2.10.1/go.mod h1:FwWsfWEjyV/CMj8s/gqAuiviY72rJ1/oayI9WftqcKg=
+github.com/hashicorp/hcl-lang v0.0.0-20220316204834-49ffde67ce68 h1:CdUL7gJYGdJheCfAmCWNE65wimdo9YWJSqB/+NtfWPc=
+github.com/hashicorp/hcl-lang v0.0.0-20220316204834-49ffde67ce68/go.mod h1:oQgcOV8OizFyZfZh3FbQSsQtvtTv8hD23MLAxfn3E+E=
 github.com/hashicorp/hcl/v2 v2.11.1 h1:yTyWcXcm9XB0TEkyU/JCRU6rYy4K+mgLtzn2wlrJbcc=
 github.com/hashicorp/hcl/v2 v2.11.1/go.mod h1:FwWsfWEjyV/CMj8s/gqAuiviY72rJ1/oayI9WftqcKg=
 github.com/hashicorp/logutils v1.0.0/go.mod h1:QIAnNjmIWmVIIkWDTG1z5v++HQmx9WQRO+LraFDTW64=
@@ -315,8 +313,8 @@ github.com/hashicorp/terraform-json v0.13.0/go.mod h1:y5OdLBCT+rxbwnpxZs9kGL7R9E
 github.com/hashicorp/terraform-registry-address v0.0.0-20210412075316-9b2996cce896/go.mod h1:bzBPnUIkI0RxauU8Dqo+2KrZZ28Cf48s8V6IHt3p4co=
 github.com/hashicorp/terraform-registry-address v0.0.0-20210816115301-cb2034eba045 h1:R/I8ofvXuPcTNoc//N4ruvaHGZcShI/VuU2iXo875Lo=
 github.com/hashicorp/terraform-registry-address v0.0.0-20210816115301-cb2034eba045/go.mod h1:anRyJbe12BZscpFgaeGu9gH12qfdBP094LYFtuAFzd4=
-github.com/hashicorp/terraform-schema v0.0.0-20220225085753-faadc57bd40a h1:zmKoQsY/7OzNElKxg8Y+GGWzWCnQsE0JBdPfY7tMqPo=
-github.com/hashicorp/terraform-schema v0.0.0-20220225085753-faadc57bd40a/go.mod h1:Y6ag6iaW+d2PwoWSLFrt+azKn4CryA+7bKUlqxD9ogQ=
+github.com/hashicorp/terraform-schema v0.0.0-20220316204916-c6585b866d6d h1:XLelo71INyUNDHQAWnGwsfAA5Ccj9LqtbaejBUzYKhc=
+github.com/hashicorp/terraform-schema v0.0.0-20220316204916-c6585b866d6d/go.mod h1:i0M64K9OfxlLRuFOThK1KRi9+20Y9XbyWpgPaEycbec=
 github.com/hashicorp/terraform-svchost v0.0.0-20200729002733-f050f53b9734 h1:HKLsbzeOsfXmKNpr3GiT18XAblV0BjCbzL8KQAMZGa0=
 github.com/hashicorp/terraform-svchost v0.0.0-20200729002733-f050f53b9734/go.mod h1:kNDNcF7sN4DocDLBkQYz73HGKwN1ANB1blq4lIYLYvg=
 github.com/huandu/xstrings v1.3.2 h1:L18LIDzqlW6xN2rEkpdV8+oL/IXWJ1APd+vsdYy4Wdw=
@@ -811,7 +809,6 @@ golang.org/x/tools v0.1.4/go.mod h1:o0xws9oXOQQZyjljx8fwUC0k7L1pTE6eaCbjGeHmOkk=
 golang.org/x/tools v0.1.5/go.mod h1:o0xws9oXOQQZyjljx8fwUC0k7L1pTE6eaCbjGeHmOkk=
 golang.org/x/tools v0.1.7/go.mod h1:LGqMHiF4EqQNHR1JncWGqT5BVaXmza+X+BDGol+dOxo=
 golang.org/x/tools v0.1.8/go.mod h1:nABZi5QlRsZVlzPpHl034qft6wpY4eDcsTt5AaioBiU=
-golang.org/x/tools v0.1.9/go.mod h1:nABZi5QlRsZVlzPpHl034qft6wpY4eDcsTt5AaioBiU=
 golang.org/x/tools v0.1.10 h1:QjFRCZxdOhBJ/UNgnBZLbNV13DlbnK0quyivTnXJM20=
 golang.org/x/tools v0.1.10/go.mod h1:Uh6Zz+xoGYZom868N8YTex3t7RhtHDBrE8Gzo9bV56E=
 golang.org/x/xerrors v0.0.0-20190717185122-a985d3407aa7/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=

internal/lsp/semantic_tokens.go

@@ -1,9 +1,66 @@
 package lsp
 
 import (
+	"github.com/hashicorp/hcl-lang/lang"
+	"github.com/hashicorp/terraform-ls/internal/lsp/semtok"
 	lsp "github.com/hashicorp/terraform-ls/internal/protocol"
+	tfschema "github.com/hashicorp/terraform-schema/schema"
 )
 
+// Registering types which are actually in use
+var (
+	serverTokenTypes = semtok.TokenTypes{
+		semtok.TokenTypeEnumMember,
+		semtok.TokenTypeFunction,
+		semtok.TokenTypeKeyword,
+		semtok.TokenTypeNumber,
+		semtok.TokenTypeParameter,
+		semtok.TokenTypeProperty,
+		semtok.TokenTypeString,
+		semtok.TokenTypeType,
+		semtok.TokenTypeVariable,
+	}
+	serverTokenModifiers = semtok.TokenModifiers{
+		semtok.TokenModifierDefaultLibrary,
+	}
+)
+
+func init() {
+	for _, tokType := range lang.SupportedSemanticTokenTypes {
+		serverTokenTypes = append(serverTokenTypes, semtok.TokenType(tokType))
+	}
+	serverTokenModifiers = append(serverTokenModifiers, semtok.TokenModifier(lang.TokenModifierDependent))
+	for _, tokModifier := range tfschema.SemanticTokenModifiers {
+		serverTokenModifiers = append(serverTokenModifiers, semtok.TokenModifier(tokModifier))
+	}
+}
+
+func TokenTypesLegend(clientSupported []string) semtok.TokenTypes {
+	legend := make(semtok.TokenTypes, 0)
+
+	// Filter only supported token types
+	for _, tokenType := range serverTokenTypes {
+		if sliceContains(clientSupported, string(tokenType)) {
+			legend = append(legend, semtok.TokenType(tokenType))
+		}
+	}
+
+	return legend
+}
+
+func TokenModifiersLegend(clientSupported []string) semtok.TokenModifiers {
+	legend := make(semtok.TokenModifiers, 0)
+
+	// Filter only supported token modifiers
+	for _, modifier := range serverTokenModifiers {
+		if sliceContains(clientSupported, string(modifier)) {
+			legend = append(legend, semtok.TokenModifier(modifier))
+		}
+	}
+
+	return legend
+}
+
 type SemanticTokensClientCapabilities struct {
 	lsp.SemanticTokensClientCapabilities
 }

internal/lsp/semtok/lsp_token_modifiers.go

@@ -0,0 +1,15 @@
+package semtok
+
+var (
+	// Modifiers predefined in LSP spec
+	TokenModifierDeclaration    TokenModifier = "declaration"
+	TokenModifierDefinition     TokenModifier = "definition"
+	TokenModifierReadonly       TokenModifier = "readonly"
+	TokenModifierStatic         TokenModifier = "static"
+	TokenModifierDeprecated     TokenModifier = "deprecated"
+	TokenModifierAbstract       TokenModifier = "abstract"
+	TokenModifierAsync          TokenModifier = "async"
+	TokenModifierModification   TokenModifier = "modification"
+	TokenModifierDocumentation  TokenModifier = "documentation"
+	TokenModifierDefaultLibrary TokenModifier = "defaultLibrary"
+)

internal/lsp/semtok/lsp_token_types.go

@@ -0,0 +1,27 @@
+package semtok
+
+const (
+	// Types predefined in LSP spec
+	TokenTypeClass         TokenType = "class"
+	TokenTypeComment       TokenType = "comment"
+	TokenTypeEnum          TokenType = "enum"
+	TokenTypeEnumMember    TokenType = "enumMember"
+	TokenTypeEvent         TokenType = "event"
+	TokenTypeFunction      TokenType = "function"
+	TokenTypeInterface     TokenType = "interface"
+	TokenTypeKeyword       TokenType = "keyword"
+	TokenTypeMacro         TokenType = "macro"
+	TokenTypeMethod        TokenType = "method"
+	TokenTypeModifier      TokenType = "modifier"
+	TokenTypeNamespace     TokenType = "namespace"
+	TokenTypeNumber        TokenType = "number"
+	TokenTypeOperator      TokenType = "operator"
+	TokenTypeParameter     TokenType = "parameter"
+	TokenTypeProperty      TokenType = "property"
+	TokenTypeRegexp        TokenType = "regexp"
+	TokenTypeString        TokenType = "string"
+	TokenTypeStruct        TokenType = "struct"
+	TokenTypeType          TokenType = "type"
+	TokenTypeTypeParameter TokenType = "typeParameter"
+	TokenTypeVariable      TokenType = "variable"
+)

internal/lsp/semtok/token_modifier.go

@@ -0,0 +1,37 @@
+package semtok
+
+import "math"
+
+type TokenModifier string
+type TokenModifiers []TokenModifier
+
+func (tm TokenModifiers) AsStrings() []string {
+	modifiers := make([]string, len(tm))
+
+	for i, tokenModifier := range tm {
+		modifiers[i] = string(tokenModifier)
+	}
+
+	return modifiers
+}
+
+func (tm TokenModifiers) BitMask(declaredModifiers TokenModifiers) int {
+	bitMask := 0b0
+
+	for i, modifier := range tm {
+		if isDeclared(modifier, declaredModifiers) {
+			bitMask |= int(math.Pow(2, float64(i)))
+		}
+	}
+
+	return bitMask
+}
+
+func isDeclared(mod TokenModifier, declaredModifiers TokenModifiers) bool {
+	for _, dm := range declaredModifiers {
+		if mod == dm {
+			return true
+		}
+	}
+	return false
+}

internal/lsp/semtok/token_types.go

@@ -0,0 +1,23 @@
+package semtok
+
+type TokenType string
+type TokenTypes []TokenType
+
+func (tt TokenTypes) AsStrings() []string {
+	types := make([]string, len(tt))
+
+	for i, tokenType := range tt {
+		types[i] = string(tokenType)
+	}
+
+	return types
+}
+
+func (tt TokenTypes) Index(tokenType TokenType) int {
+	for i, t := range tt {
+		if t == tokenType {
+			return i
+		}
+	}
+	return -1
+}