interp: Move *CtxWriter to ioextra, some comments cleanup

internal/ioextra/ioextra.go

@@ -1,6 +1,7 @@
 package ioextra
 
 import (
+	"context"
 	"errors"
 	"io"
 )
@@ -26,3 +27,30 @@ type ReadErrSeeker struct{ io.Reader }
 func (r *ReadErrSeeker) Seek(offset int64, whence int) (int64, error) {
 	return 0, errors.New("seek")
 }
+
+type CtxWriter struct {
+	io.Writer
+	Ctx context.Context
+}
+
+func (o CtxWriter) Write(p []byte) (n int, err error) {
+	if o.Ctx != nil {
+		if err := o.Ctx.Err(); err != nil {
+			return 0, err
+		}
+	}
+	return o.Writer.Write(p)
+}
+
+type DiscardCtxWriter struct {
+	Ctx context.Context
+}
+
+func (o DiscardCtxWriter) Write(p []byte) (n int, err error) {
+	if o.Ctx != nil {
+		if err := o.Ctx.Err(); err != nil {
+			return 0, err
+		}
+	}
+	return n, nil
+}

internal/ioextra/runereader.go

@@ -6,8 +6,9 @@ import (
 	"unicode/utf8"
 )
 
-// ByteRuneReader reads each by as a runes from a io.ReadSeeker
-// ex: when used with regexp \u00ff code point will match byte 0xff and not the utf-8 encoded version of 0xff
+// ByteRuneReader reads each byte as a rune from a io.ReadSeeker
+// ex: when used with regexp \u00ff code point will match byte 0xff and not the
+// utf-8 encoded version of 0xff
 type ByteRuneReader struct {
 	RS io.ReadSeeker
 }
@@ -46,7 +47,7 @@ func utf8Bytes(b byte) int {
 	}
 }
 
-// RuneReadSeeker reads runs from a io.ReadSeeker
+// RuneReadSeeker reads rune from a io.ReadSeeker
 func (brr RuneReadSeeker) ReadRune() (r rune, size int, err error) {
 	var b [utf8.UTFMax]byte
 

pkg/interp/funcs.go

@@ -225,8 +225,13 @@ func (i *Interp) readline(c interface{}, a []interface{}) interface{} {
 			}
 
 			names, shared, err := func() (newLine []string, shared int, err error) {
+				// c | opts.Complete(line; pos)
 				vs, err := i.EvalFuncValues(
-					completeCtx, c, opts.Complete, []interface{}{line, pos}, DiscardCtxWriter{Ctx: completeCtx},
+					completeCtx,
+					c,
+					opts.Complete,
+					[]interface{}{line, pos},
+					ioextra.DiscardCtxWriter{Ctx: completeCtx},
 				)
 				if err != nil {
 					return nil, pos, err
@@ -519,7 +524,10 @@ func (i *Interp) _open(c interface{}, a []interface{}) interface{} {
 		return err
 	}
 
-	// TODO: ctxreadseeker might leak
+	// ctxreadseeker is used to make sure any io calls can be canceled
+	// TODO: ctxreadseeker might leak if the underlaying call hangs forever
+
+	// a regular file should be seekable but fallback below to read whole file if not
 	if fFI.Mode().IsRegular() {
 		if rs, ok := f.(io.ReadSeeker); ok {
 			fRS = ctxreadseeker.New(i.evalContext.ctx, rs)
@@ -554,7 +562,7 @@ func (i *Interp) _open(c interface{}, a []interface{}) interface{} {
 	const cacheReadAheadSize = 512 * 1024
 	aheadRs := aheadreadseeker.New(fRS, cacheReadAheadSize)
 
-	// bb -> aheadreadseeker -> progressreadseeker -> ctxreadseeker -> readerseeker
+	// bitio.Buffer -> aheadreadseeker -> progressreadseeker -> ctxreadseeker -> readseeker
 
 	bbf.bb, err = bitio.NewBufferFromReadSeeker(aheadRs)
 	if err != nil {
@@ -581,12 +589,13 @@ func (i *Interp) _decode(c interface{}, a []interface{}) interface{} {
 
 		if opts.Progress != "" {
 			evalProgress := func(c interface{}) {
+				// {approx_read_bytes: 123, total_size: 123} | opts.Progress
 				_, _ = i.EvalFuncValues(
 					i.evalContext.ctx,
 					c,
 					opts.Progress,
 					nil,
-					DiscardCtxWriter{Ctx: i.evalContext.ctx},
+					ioextra.DiscardCtxWriter{Ctx: i.evalContext.ctx},
 				)
 			}
 			bbf.progressFn = func(approxReadBytes, totalSize int64) {

pkg/interp/internal.jq

@@ -96,7 +96,7 @@ def _eval_compile_error_tostring:
   "\(.filename // "src"):\(.line):\(.column): \(.error)";
 def _eval($expr; $filename; f; on_error; on_compile_error):
   try
-      eval($expr; $filename) | f
+    eval($expr; $filename) | f
   catch
     if _eval_is_compile_error then on_compile_error
     else on_error

pkg/interp/interp.go

@@ -22,6 +22,7 @@ import (
 	"github.com/wader/fq/internal/ansi"
 	"github.com/wader/fq/internal/colorjson"
 	"github.com/wader/fq/internal/ctxstack"
+	"github.com/wader/fq/internal/ioextra"
 	"github.com/wader/fq/internal/num"
 	"github.com/wader/fq/internal/pos"
 	"github.com/wader/fq/pkg/bitio"
@@ -110,7 +111,7 @@ type OS interface {
 	Args() []string
 	Environ() []string
 	ConfigDir() (string, error)
-	// returned Open() io.ReadSeeker can optionally implement io.Closer
+	// FS.File returned by FS().Open() can optionally implement io.Seeker
 	FS() fs.FS
 	Readline(prompt string, complete func(line string, pos int) (newLine []string, shared int)) (string, error)
 	History() ([]string, error)
@@ -141,34 +142,6 @@ func (rf FileReader) Stat() (fs.FileInfo, error) { return rf.FileInfo, nil }
 func (rf FileReader) Read(p []byte) (int, error) { return rf.R.Read(p) }
 func (FileReader) Close() error                  { return nil }
 
-// TODO: move
-type DiscardCtxWriter struct {
-	Ctx context.Context
-}
-
-func (o DiscardCtxWriter) Write(p []byte) (n int, err error) {
-	if o.Ctx != nil {
-		if err := o.Ctx.Err(); err != nil {
-			return 0, err
-		}
-	}
-	return n, nil
-}
-
-type CtxWriter struct {
-	io.Writer
-	Ctx context.Context
-}
-
-func (o CtxWriter) Write(p []byte) (n int, err error) {
-	if o.Ctx != nil {
-		if err := o.Ctx.Err(); err != nil {
-			return 0, err
-		}
-	}
-	return o.Writer.Write(p)
-}
-
 type Value interface {
 	gojq.JQValue
 
@@ -711,7 +684,7 @@ func (i *Interp) Eval(ctx context.Context, c interface{}, src string, srcFilenam
 
 	runCtx, runCtxCancelFn := i.interruptStack.Push(ctx)
 	ni.evalContext.ctx = runCtx
-	ni.evalContext.output = CtxWriter{Writer: output, Ctx: runCtx}
+	ni.evalContext.output = ioextra.CtxWriter{Writer: output, Ctx: runCtx}
 	iter := gc.RunWithContext(runCtx, c, variableValues...)
 
 	iterWrapper := iterFn(func() (interface{}, bool) {