Optimize didChange for single files

- detect if file has already been parsed and rpc request is for didChange
- only process changed file if above is true

internal/context/context.go

@@ -186,3 +186,7 @@ func WithRPCContext(ctx context.Context, rpcc RPCContextData) context.Context {
 func RPCContext(ctx context.Context) RPCContextData {
 	return ctx.Value(ctxRPCContext).(RPCContextData)
 }
+
+func (ctxData RPCContextData) IsDidChangeRequest() bool{
+	return ctxData.Method == "textDocument/didChange"
+}

internal/decoder/decoder_test.go

@@ -18,6 +18,7 @@ import (
 
 	"github.com/hashicorp/hcl-lang/decoder"
 	"github.com/hashicorp/hcl-lang/lang"
+	lsctx "github.com/hashicorp/terraform-ls/internal/context"
 	idecoder "github.com/hashicorp/terraform-ls/internal/decoder"
 	"github.com/hashicorp/terraform-ls/internal/state"
 	"github.com/hashicorp/terraform-ls/internal/terraform/module"
@@ -60,6 +61,7 @@ func TestDecoder_CodeLensesForFile_concurrencyBug(t *testing.T) {
 		if err != nil {
 			t.Error(err)
 		}
+		ctx = lsctx.WithRPCContext(ctx, lsctx.RPCContextData{})
 		err = module.ParseModuleConfiguration(ctx, mapFs, ss.Modules, dirName)
 		if err != nil {
 			t.Error(err)

internal/terraform/module/module_ops.go

@@ -18,16 +18,19 @@ import (
 	"github.com/hashicorp/hcl-lang/decoder"
 	"github.com/hashicorp/hcl-lang/lang"
 	tfjson "github.com/hashicorp/terraform-json"
+	lsctx "github.com/hashicorp/terraform-ls/internal/context"
 	idecoder "github.com/hashicorp/terraform-ls/internal/decoder"
 	"github.com/hashicorp/terraform-ls/internal/document"
 	"github.com/hashicorp/terraform-ls/internal/job"
 	ilsp "github.com/hashicorp/terraform-ls/internal/lsp"
 	"github.com/hashicorp/terraform-ls/internal/registry"
 	"github.com/hashicorp/terraform-ls/internal/schemas"
 	"github.com/hashicorp/terraform-ls/internal/state"
+	"github.com/hashicorp/terraform-ls/internal/terraform/ast"
 	"github.com/hashicorp/terraform-ls/internal/terraform/datadir"
 	op "github.com/hashicorp/terraform-ls/internal/terraform/module/operation"
 	"github.com/hashicorp/terraform-ls/internal/terraform/parser"
+	"github.com/hashicorp/terraform-ls/internal/uri"
 	tfaddr "github.com/hashicorp/terraform-registry-address"
 	"github.com/hashicorp/terraform-schema/earlydecoder"
 	"github.com/hashicorp/terraform-schema/module"
@@ -359,19 +362,32 @@ func ParseModuleConfiguration(ctx context.Context, fs ReadOnlyFS, modStore *stat
 
 	// TODO: Avoid parsing if the content matches existing AST
 
-	// TODO: Only parse the file that's being changed/opened, unless this is 1st-time parsing
-
 	// Avoid parsing if it is already in progress or already known
 	if mod.ModuleParsingState != op.OpStateUnknown && !job.IgnoreState(ctx) {
 		return job.StateNotChangedErr{Dir: document.DirHandleFromPath(modPath)}
 	}
 
-	err = modStore.SetModuleParsingState(modPath, op.OpStateLoading)
+	var files ast.ModFiles
+	var diags ast.ModDiags
+	rpcContext := lsctx.RPCContext(ctx)
+	// Only parse the file that's being changed/opened, unless this is 1st-time parsing
+	if mod.ModuleParsingState == op.OpStateLoaded && rpcContext.IsDidChangeRequest() {
+		// the file has already been parsed, so only examine this file and not the whole module
+		fileName, _ := uri.PathFromURI(rpcContext.URI)
+		files, diags, err = parser.ParseModuleFile(fs, fileName)
+	} else {
+		// this is the first time file is opened so parse the whole module
+		files, diags, err = parser.ParseModuleFiles(fs, modPath)
+	}
+
 	if err != nil {
 		return err
 	}
 
-	files, diags, err := parser.ParseModuleFiles(fs, modPath)
+	err = modStore.SetModuleParsingState(modPath, op.OpStateLoading)
+	if err != nil {
+		return err
+	}
 
 	sErr := modStore.UpdateParsedModuleFiles(modPath, files, err)
 	if sErr != nil {

internal/terraform/module/module_ops_test.go

@@ -23,6 +23,7 @@ import (
 	"github.com/hashicorp/go-version"
 	"github.com/hashicorp/hcl-lang/lang"
 	tfjson "github.com/hashicorp/terraform-json"
+	lsctx "github.com/hashicorp/terraform-ls/internal/context"
 	"github.com/hashicorp/terraform-ls/internal/document"
 	"github.com/hashicorp/terraform-ls/internal/filesystem"
 	"github.com/hashicorp/terraform-ls/internal/job"
@@ -56,6 +57,7 @@ func TestGetModuleDataFromRegistry_singleModule(t *testing.T) {
 	}
 
 	fs := filesystem.NewFilesystem(ss.DocumentStore)
+	ctx = lsctx.WithRPCContext(ctx, lsctx.RPCContextData{})
 	err = ParseModuleConfiguration(ctx, fs, ss.Modules, modPath)
 	if err != nil {
 		t.Fatal(err)
@@ -128,6 +130,7 @@ func TestGetModuleDataFromRegistry_moduleNotFound(t *testing.T) {
 	}
 
 	fs := filesystem.NewFilesystem(ss.DocumentStore)
+	ctx = lsctx.WithRPCContext(ctx, lsctx.RPCContextData{})
 	err = ParseModuleConfiguration(ctx, fs, ss.Modules, modPath)
 	if err != nil {
 		t.Fatal(err)
@@ -228,6 +231,7 @@ func TestGetModuleDataFromRegistry_apiTimeout(t *testing.T) {
 	}
 
 	fs := filesystem.NewFilesystem(ss.DocumentStore)
+	ctx = lsctx.WithRPCContext(ctx, lsctx.RPCContextData{})
 	err = ParseModuleConfiguration(ctx, fs, ss.Modules, modPath)
 	if err != nil {
 		t.Fatal(err)
@@ -522,6 +526,7 @@ func TestParseProviderVersions_multipleVersions(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
+	ctx = lsctx.WithRPCContext(ctx, lsctx.RPCContextData{})
 	err = ParseModuleConfiguration(ctx, fs, ss.Modules, modPathFirst)
 	if err != nil {
 		t.Fatal(err)
@@ -691,6 +696,7 @@ func TestPreloadEmbeddedSchema_basic(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
+	ctx = lsctx.WithRPCContext(ctx, lsctx.RPCContextData{})
 	err = ParseModuleConfiguration(ctx, cfgFS, ss.Modules, modPath)
 	if err != nil {
 		t.Fatal(err)
@@ -761,6 +767,7 @@ func TestPreloadEmbeddedSchema_unknownProviderOnly(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
+	ctx = lsctx.WithRPCContext(ctx, lsctx.RPCContextData{})
 	err = ParseModuleConfiguration(ctx, cfgFS, ss.Modules, modPath)
 	if err != nil {
 		t.Fatal(err)
@@ -824,6 +831,7 @@ func TestPreloadEmbeddedSchema_idempotency(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
+	ctx = lsctx.WithRPCContext(ctx, lsctx.RPCContextData{})
 	err = ParseModuleConfiguration(ctx, cfgFS, ss.Modules, modPath)
 	if err != nil {
 		t.Fatal(err)
@@ -903,6 +911,7 @@ func TestPreloadEmbeddedSchema_raceCondition(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
+	ctx = lsctx.WithRPCContext(ctx, lsctx.RPCContextData{})
 	err = ParseModuleConfiguration(ctx, cfgFS, ss.Modules, modPath)
 	if err != nil {
 		t.Fatal(err)

internal/terraform/parser/module.go

@@ -52,3 +52,26 @@ func ParseModuleFiles(fs FS, modPath string) (ast.ModFiles, ast.ModDiags, error)
 
 	return files, diags, nil
 }
+
+func ParseModuleFile(fs FS, fileName string) (ast.ModFiles, ast.ModDiags, error) {
+	files := make(ast.ModFiles, 0)
+	diags := make(ast.ModDiags, 0)
+
+	src, err := fs.ReadFile(fileName)
+	if err != nil {
+		// If a file isn't accessible, return
+		return nil, nil, err
+	}
+
+	name := filepath.Base((fileName))
+	filename := ast.ModFilename(name)
+
+	f, pDiags := parseFile(src, filename)
+
+	diags[filename] = pDiags
+	if f != nil {
+		files[filename] = f
+	}
+
+	return files, diags, nil
+}