command: Show snippet of invalid resource addresses in import

If we fail to parse the resource address given to "terraform import" then
it's helpful to produce a "source code" snippet of what the user provided
so they might see more precisely which part of the address was invalid.

command/import.go

@@ -62,9 +62,11 @@ func (c *ImportCommand) Run(args []string) int {
 	var diags tfdiags.Diagnostics
 
 	// Parse the provided resource address.
-	traversal, travDiags := hclsyntax.ParseTraversalAbs([]byte(args[0]), "<import-address>", hcl.Pos{Line: 1, Column: 1})
+	traversalSrc := []byte(args[0])
+	traversal, travDiags := hclsyntax.ParseTraversalAbs(traversalSrc, "<import-address>", hcl.Pos{Line: 1, Column: 1})
 	diags = diags.Append(travDiags)
 	if travDiags.HasErrors() {
+		c.registerSynthConfigSource("<import-address>", traversalSrc) // so we can include a source snippet
 		c.showDiagnostics(diags)
 		c.Ui.Info(importCommandInvalidAddressReference)
 		return 1
@@ -72,6 +74,7 @@ func (c *ImportCommand) Run(args []string) int {
 	addr, addrDiags := addrs.ParseAbsResourceInstance(traversal)
 	diags = diags.Append(addrDiags)
 	if addrDiags.HasErrors() {
+		c.registerSynthConfigSource("<import-address>", traversalSrc) // so we can include a source snippet
 		c.showDiagnostics(diags)
 		c.Ui.Info(importCommandInvalidAddressReference)
 		return 1

command/import_test.go

@@ -594,7 +594,7 @@ func TestImport_dataResource(t *testing.T) {
 	}
 
 	msg := ui.ErrorWriter.String()
-	if want := `resource address must refer to a managed resource`; !strings.Contains(msg, want) {
+	if want := `A managed resource address is required`; !strings.Contains(msg, want) {
 		t.Errorf("incorrect message\nwant substring: %s\ngot:\n%s", want, msg)
 	}
 }
@@ -624,7 +624,7 @@ func TestImport_invalidResourceAddr(t *testing.T) {
 	}
 
 	msg := ui.ErrorWriter.String()
-	if want := `invalid resource address "bananas"`; !strings.Contains(msg, want) {
+	if want := `Error: Invalid address`; !strings.Contains(msg, want) {
 		t.Errorf("incorrect message\nwant substring: %s\ngot:\n%s", want, msg)
 	}
 }
@@ -654,7 +654,7 @@ func TestImport_targetIsModule(t *testing.T) {
 	}
 
 	msg := ui.ErrorWriter.String()
-	if want := `resource address must include a full resource spec`; !strings.Contains(msg, want) {
+	if want := `Error: Invalid address`; !strings.Contains(msg, want) {
 		t.Errorf("incorrect message\nwant substring: %s\ngot:\n%s", want, msg)
 	}
 }

command/meta_config.go

@@ -309,6 +309,25 @@ func (m *Meta) modulesDir() string {
 	return filepath.Join(m.DataDir(), "modules")
 }
 
+// registerSynthConfigSource allows commands to add synthetic additional source
+// buffers to the config loader's cache of sources (as returned by
+// configSources), which is useful when a command is directly parsing something
+// from the command line that may produce diagnostics, so that diagnostic
+// snippets can still be produced.
+//
+// If this is called before a configLoader has been initialized then it will
+// try to initialize the loader but ignore any initialization failure, turning
+// the call into a no-op. (We presume that a caller will later call a different
+// function that also initializes the config loader as a side effect, at which
+// point those errors can be returned.)
+func (m *Meta) registerSynthConfigSource(filename string, src []byte) {
+	loader, err := m.initConfigLoader()
+	if err != nil || loader == nil {
+		return // treated as no-op, since this is best-effort
+	}
+	loader.Parser().ForceFileSource(filename, src)
+}
+
 // initConfigLoader initializes the shared configuration loader if it isn't
 // already initialized.
 //