fix the charm library's terminal error handling

doesn't affect tell, but tapestry is using charm for some manual string parsing.
- exit ParseEof when using charm.Finished()
- wrap Endpoint errors instead of embedding the reason as a string
- changes for staticcheck

charm/charmParse.go

@@ -26,16 +26,17 @@ func innerParse(first State, in io.RuneReader) (ret State, err error) {
 	for i := 0; ; i++ {
 		if r, _, e := in.ReadRune(); e != nil {
 			if e != io.EOF {
-				err = errors.Join(e, EndpointError{errContext(r, in), i, try, e.Error()})
+				err = errors.Join(e, EndpointError{r, in, i, try})
 			}
 			break
 		} else {
 			if next := try.NewRune(r); next == nil {
 				// no states left to parse remaining input
-				err = EndpointError{errContext(r, in), i, try, "unhandled rune"}
+				e := errors.New("unhandled rune")
+				err = errors.Join(e, EndpointError{r, in, i, try})
 				break
 			} else if es, ok := next.(Terminal); ok {
-				err = EndpointError{errContext(r, in), i, try, es.err.Error()}
+				err = errors.Join(es.err, EndpointError{r, in, i, try})
 				break
 			} else {
 				try = next
@@ -72,11 +73,8 @@ func ParseEof(str string, first State) (err error) {
 		err = e
 	} else if last != nil {
 		if fini := last.NewRune(Eof); fini != nil {
-			if es, ok := fini.(Terminal); ok && es.err != nil {
-				err = fmt.Errorf("%s handling eof for %q", es.err, str)
-			} else {
-				// and if we are passing eof, shouldnt the states check for it and return nil?
-				// err = EndpointError{str, len(str), fini}
+			if es, ok := fini.(Terminal); !ok || !es.Finished() {
+				err = fmt.Errorf("%s at eof for %q", es.err, str)
 			}
 		}
 	}
@@ -85,10 +83,10 @@ func ParseEof(str string, first State) (err error) {
 
 // ended before the whole input was parsed.
 type EndpointError struct {
-	str    string
-	end    int
-	last   State
-	reason string
+	r    rune
+	in   io.RuneReader
+	end  int
+	last State
 }
 
 // index of the failure point in the input
@@ -97,6 +95,6 @@ func (e EndpointError) End() int {
 }
 
 func (e EndpointError) Error() (ret string) {
-	return fmt.Sprintf("%s %q (%q ended at index %d)",
-		e.reason, e.str, StateName(e.last), e.end)
+	sink := errContext(e.r, e.in)
+	return fmt.Sprintf("%q (%q ended at index %d)", sink, StateName(e.last), e.end)
 }

charm/charmRequires_test.go

@@ -12,11 +12,12 @@ func TestRequires(t *testing.T) {
 
 	// index of the fail point, or -1 if success is expected
 	count := func(failPoint int, str string, style State) (err error) {
+		var ep EndpointError
 		if e := ParseEof(str, style); e == nil && failPoint != -1 {
 			err = errors.New("unexpected success")
-		} else if n, ok := e.(EndpointError); !ok {
+		} else if !errors.As(e, &ep) {
 			err = e
-		} else if at := n.End(); at != failPoint {
+		} else if at := ep.End(); at != failPoint {
 			// 0 means okay, -1 incomplete, >0 the one-index of the failure point.
 			err = fmt.Errorf("%s len: %d", str, at)
 		}

charmed/charmedHeader.go

@@ -58,7 +58,7 @@ func (h *headCount) update(q rune, report headerNotifier) (err error) {
 	} else if prev, width := h.token, h.width; t == prev {
 		h.width++
 	} else if prev == headerRedirect && width != 3 {
-		err = customTagError
+		err = errCustomTag
 	} else {
 		h.token, h.width = t, 1
 		if prev != headerSpaces {
@@ -70,7 +70,7 @@ func (h *headCount) update(q rune, report headerNotifier) (err error) {
 	return
 }
 
-var customTagError = errors.New("custom closing tags require exactly three redirect markers ('<<<')")
+var errCustomTag = errors.New("custom closing tags require exactly three redirect markers ('<<<')")
 
 // determine which header type, if any, the passed rune belongs to
 // ( false if its some classifiable rune )

charmed/charmedNum.go

@@ -29,7 +29,6 @@ func (*NumParser) String() string {
 	return "Numbers"
 }
 
-
 // fix: this is currently less of a number parser, and more a number validator.
 func (p *NumParser) accept(q rune, s charm.State) charm.State {
 	p.runes.WriteRune(q)
@@ -46,7 +45,7 @@ func (p *NumParser) GetNumber() (ret any, err error) {
 	case modeFloat:
 		ret = fromFloat(s)
 	default:
-		err = fmt.Errorf("unknown number: '%v' is %v.", s, p.mode)
+		err = fmt.Errorf("unknown number: '%v' is %v", s, p.mode)
 	}
 	return
 }
@@ -61,7 +60,7 @@ func (p *NumParser) GetFloat() (ret float64, err error) {
 	case modeFloat:
 		ret = fromFloat(s)
 	default:
-		err = fmt.Errorf("unknown number: '%v' is %v.", s, p.mode)
+		err = fmt.Errorf("unknown number: '%v' is %v", s, p.mode)
 	}
 	return
 }

charmed/charmedNum_test.go

@@ -1,6 +1,7 @@
 package charmed
 
 import (
+	"errors"
 	"math"
 	"testing"
 
@@ -85,10 +86,11 @@ func TestNum(t *testing.T) {
 				t.Fatal("expected success", e)
 				break
 			} else if test.endpoint > 0 {
-				if c, ok := e.(charm.EndpointError); !ok {
+				var ep charm.EndpointError
+				if !errors.As(e, &ep) {
 					t.Fatal("unexpected error", e)
 					break
-				} else if c.End() != test.endpoint-1 {
+				} else if ep.End() != test.endpoint-1 {
 					t.Fatal("mismatched endpoint at", e)
 					break
 				}

decode/decodeArray.go

@@ -24,7 +24,7 @@ func (d *Decoder) waitForSep(at token.Pos, tokenType token.Type, val any) (err e
 				d.state = d.waitForEl
 			}
 		default:
-			err = errors.New("expected an array separator, or array close.")
+			err = errors.New("expected an array separator or array close")
 		}
 	}
 	return

encode/encodeMap.go

@@ -42,7 +42,7 @@ func keyTransform(v r.Value) (ret string) {
 	return
 }
 
-func (m *MapTransform) makeMapping(src r.Value) (retIt Iterator, err error) {
+func (m *MapTransform) makeMapping(src r.Value) (Iterator, error) {
 	keyLess := m.keyLess
 	if keyLess == nil {
 		keyLess = func(a, b string) bool { return a < b }
@@ -62,16 +62,10 @@ func (m *MapTransform) makeMapping(src r.Value) (retIt Iterator, err error) {
 		mk = mapKeys{str: str, val: keys, keyLess: keyLess}
 		sort.Sort(&mk)
 	}
-	if err == nil {
-		retIt = &mapIter{src: src, mapKeys: mk}
-	}
-	return
+	//
+	return &mapIter{src: src, mapKeys: mk}, nil
 }
 
-// not quite sure how to turn string into an interface without something like this. ugh.
-var anyBlank = [1]any{""}
-var blank = r.ValueOf(anyBlank).Index(0)
-
 type mapIter struct {
 	src     r.Value // the native map
 	mapKeys mapKeys

token/tokens.go

@@ -151,7 +151,7 @@ func (n *tokenizer) wordDecoder() charm.State {
 				} else if terminal(sign) {
 					// sign is mostly superset of bool; (except for the eof/eol cases)
 					// if it dies and boolean didnt just succeed; they're both dead.
-					ret = charm.Error(wordyError)
+					ret = charm.Error(errWordy)
 				}
 				return
 			})
@@ -169,7 +169,7 @@ func (n *tokenizer) decodeSignature() charm.State {
 		if sign = sign.NewRune(q); sign == nil {
 			ret = n.notifyRune(q, Key, sig.String())
 		} else if terminal(sign) {
-			ret = charm.Error(wordyError)
+			ret = charm.Error(errWordy)
 		}
 		return
 	})
@@ -248,7 +248,7 @@ const (
 	boolTrue              // true
 )
 
-var wordyError = errors.New("couldn't read words. strings should be quoted, booleans should be 'true' or 'false', and map keys should start with a letter and end with a colon.")
+var errWordy = errors.New("couldn't read words. strings should be quoted, booleans should be 'true' or 'false', and map keys should start with a letter and end with a colon")
 
 // is the next state an error?
 func terminal(next charm.State) (okay bool) {