Update ParseVariables for single files

Modifies ParsedVarsFiles to only re-parse the single tfvars file which is being changed, if the job was scheduled as part of `textDocument/didChange` request.

This is a follow up to #1404 which updated the parsing job for terraform files.

internal/terraform/ast/variables.go

@@ -52,6 +52,14 @@ func VarsFilesFromMap(m map[string]*hcl.File) VarsFiles {
 	return mf
 }
 
+func (mf VarsFiles) Copy() VarsFiles {
+	m := make(VarsFiles, len(mf))
+	for name, file := range mf {
+		m[name] = file
+	}
+	return m
+}
+
 type VarsDiags map[VarsFilename]hcl.Diagnostics
 
 func VarsDiagsFromMap(m map[string]hcl.Diagnostics) VarsDiags {
@@ -62,6 +70,14 @@ func VarsDiagsFromMap(m map[string]hcl.Diagnostics) VarsDiags {
 	return mf
 }
 
+func (mf VarsDiags) Copy() VarsDiags {
+	m := make(VarsDiags, len(mf))
+	for name, file := range mf {
+		m[name] = file
+	}
+	return m
+}
+
 func (vd VarsDiags) AutoloadedOnly() VarsDiags {
 	diags := make(VarsDiags)
 	for name, f := range vd {

internal/terraform/module/module_ops.go

@@ -440,20 +440,58 @@ func ParseVariables(ctx context.Context, fs ReadOnlyFS, modStore *state.ModuleSt
 
 	// 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.VarsDiagnosticsState[ast.HCLParsingSource] != op.OpStateUnknown && !job.IgnoreState(ctx) {
 		return job.StateNotChangedErr{Dir: document.DirHandleFromPath(modPath)}
 	}
 
-	err = modStore.SetVarsDiagnosticsState(modPath, ast.HCLParsingSource, op.OpStateLoading)
+	var files ast.VarsFiles
+	var diags ast.VarsDiags
+	rpcContext := lsctx.RPCContext(ctx)
+	// Only parse the file that's being changed/opened, unless this is 1st-time parsing
+	if mod.ModuleDiagnosticsState[ast.HCLParsingSource] == op.OpStateLoaded && rpcContext.IsDidChangeRequest() && lsctx.IsLanguageId(ctx, ilsp.Tfvars.String()) {
+		// the file has already been parsed, so only examine this file and not the whole module
+		err = modStore.SetVarsDiagnosticsState(modPath, ast.HCLParsingSource, op.OpStateLoading)
+		if err != nil {
+			return err
+		}
+		filePath, err := uri.PathFromURI(rpcContext.URI)
+		if err != nil {
+			return err
+		}
+		fileName := filepath.Base(filePath)
+
+		f, vdiags, err := parser.ParseVariableFile(fs, filePath)
+		if err != nil {
+			return err
+		}
+
+		existingFiles := mod.ParsedVarsFiles.Copy()
+		existingFiles[ast.VarsFilename(fileName)] = f
+		files = existingFiles
+
+		existingDiags, ok := mod.VarsDiagnostics[ast.HCLParsingSource]
+		if !ok {
+			existingDiags = make(ast.VarsDiags)
+		} else {
+			existingDiags = existingDiags.Copy()
+		}
+		existingDiags[ast.VarsFilename(fileName)] = vdiags
+		diags = existingDiags
+	} else {
+		// this is the first time file is opened so parse the whole module
+		err = modStore.SetVarsDiagnosticsState(modPath, ast.HCLParsingSource, op.OpStateLoading)
+		if err != nil {
+			return err
+		}
+
+		files, diags, err = parser.ParseVariableFiles(fs, modPath)
+	}
+
 	if err != nil {
 		return err
 	}
 
-	files, diags, err := parser.ParseVariableFiles(fs, modPath)
-
 	sErr := modStore.UpdateParsedVarsFiles(modPath, files, err)
 	if sErr != nil {
 		return sErr

internal/terraform/module/module_ops_test.go

@@ -1018,6 +1018,7 @@ func TestParseModuleConfiguration(t *testing.T) {
 		t.Fatal("diags should match")
 	}
 }
+
 func TestParseModuleConfiguration_ignore_tfvars(t *testing.T) {
 	ctx := context.Background()
 	ss, err := state.NewStateStore()
@@ -1088,6 +1089,77 @@ func TestParseModuleConfiguration_ignore_tfvars(t *testing.T) {
 	}
 }
 
+func TestParseVariables(t *testing.T) {
+	ctx := context.Background()
+	ss, err := state.NewStateStore()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	testData, err := filepath.Abs("testdata")
+	if err != nil {
+		t.Fatal(err)
+	}
+	testFs := filesystem.NewFilesystem(ss.DocumentStore)
+
+	singleFileModulePath := filepath.Join(testData, "single-file-change-module")
+
+	err = ss.Modules.Add(singleFileModulePath)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	ctx = lsctx.WithLanguageId(ctx, ilsp.Tfvars.String())
+	ctx = lsctx.WithRPCContext(ctx, lsctx.RPCContextData{})
+	err = ParseModuleConfiguration(ctx, testFs, ss.Modules, singleFileModulePath)
+	if err != nil {
+		t.Fatal(err)
+	}
+	err = ParseVariables(ctx, testFs, ss.Modules, singleFileModulePath)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	before, err := ss.Modules.ModuleByPath(singleFileModulePath)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// say we're coming from did_change request
+	fooURI, err := filepath.Abs(filepath.Join(singleFileModulePath, "example.tfvars"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	x := lsctx.RPCContextData{
+		Method: "textDocument/didChange",
+		URI:    uri.FromPath(fooURI),
+	}
+
+	// ignore job state
+	ctx = job.WithIgnoreState(ctx, true)
+	ctx = lsctx.WithLanguageId(ctx, ilsp.Tfvars.String())
+	ctx = lsctx.WithRPCContext(ctx, x)
+	err = ParseVariables(ctx, testFs, ss.Modules, singleFileModulePath)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	after, err := ss.Modules.ModuleByPath(singleFileModulePath)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// example.tfvars should not be the same as first seen
+	if before.ParsedVarsFiles["example.tfvars"] == after.ParsedVarsFiles["example.tfvars"] {
+		t.Fatal("file should mismatch")
+	}
+
+	// // diags should change for example.tfvars
+	if before.VarsDiagnostics["example.tfvars"][0] == after.VarsDiagnostics["example.tfvars"][0] {
+		t.Fatal("diags should mismatch")
+	}
+}
+
 func gzipCompressBytes(t *testing.T, b []byte) []byte {
 	var compressedBytes bytes.Buffer
 	gw := gzip.NewWriter(&compressedBytes)

internal/terraform/module/testdata/single-file-change-module/example.tfvars

@@ -1,3 +1,6 @@
 variable "image_id" {
   type = string
 }
+
+# this is supposed to generate a diagnostic
+lalalalal "goo"

internal/terraform/parser/variables.go

@@ -6,6 +6,7 @@ package parser
 import (
 	"path/filepath"
 
+	"github.com/hashicorp/hcl/v2"
 	"github.com/hashicorp/terraform-ls/internal/terraform/ast"
 )
 
@@ -48,3 +49,17 @@ func ParseVariableFiles(fs FS, modPath string) (ast.VarsFiles, ast.VarsDiags, er
 
 	return files, diags, nil
 }
+
+func ParseVariableFile(fs FS, filePath string) (*hcl.File, hcl.Diagnostics, error) {
+	src, err := fs.ReadFile(filePath)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	name := filepath.Base(filePath)
+	filename := ast.VarsFilename(name)
+
+	f, pDiags := parseFile(src, filename)
+
+	return f, pDiags, nil
+}