From 394d117b90ffb64c87adfc8c2436b57007840c2b Mon Sep 17 00:00:00 2001
From: Lukasz Kasprzak <lukas@labunix.xyz>
Date: Mon, 14 Sep 2026 22:23:42 +0200
Subject: plan 10: a format with no text is no match, not unreadable

---
 docs/design.md                  |  7 +++++--
 internal/engine/exclude_test.go | 42 +++++++++++++++++++++++++++++++++++++++++
 internal/engine/facts.go        |  9 ++++++++-
 man/krino.conf.5                |  2 ++
 4 files changed, 57 insertions(+), 3 deletions(-)

diff --git a/docs/design.md b/docs/design.md
index 5b70183..a232baf 100644
--- a/docs/design.md
+++ b/docs/design.md
@@ -202,7 +202,9 @@ no rule has run yet, `(matched)` is never true inside an exclude.
 An exclude fails closed: when evaluating it reaches a content test that
 cannot read the file (over `max-read`, a tool missing, failing or timing
 out), the exclude holds, and the file is set aside as "(content
-unreadable)" with the warning. An exclude protects files, so a file krino
+unreadable)" with the warning. A file whose format has no text at all (an
+image, an archive) is not unreadable: it contains no keyword, so its
+content tests are simply false and raise no warning. An exclude protects files, so a file krino
 could not check is left alone. Mistakes in krino.conf's excludes are
 reported even while no directory is included.
 
@@ -255,7 +257,8 @@ UTF-8 is replaced by U+FFFD before folding.
    `path`, then `duplicate`, then `content`. Content is extracted at most once per file,
    and only if evaluation reaches a `content` test.
 4. If a file's text cannot be extracted, `content` is false and the plan
-   shows a warning naming the rule that wanted it. Inside an `exclude` the
+   shows a warning naming the rule that wanted it. A format with no text
+   (§6, "anything else") is not a failure: `content` is false, silently. Inside an `exclude` the
    whole exclude then holds instead (§4.6).
 
 ### 5.5 Duplicates
diff --git a/internal/engine/exclude_test.go b/internal/engine/exclude_test.go
index 87fa16c..4bb1512 100644
--- a/internal/engine/exclude_test.go
+++ b/internal/engine/exclude_test.go
@@ -260,3 +260,45 @@ func TestLoadChecksMainExcludesWithoutDirectories(t *testing.T) {
 		t.Error("a broken krino.conf exclude was not reported")
 	}
 }
+
+// TestNoTextFormatIsNoMatch: a file whose format has no text cannot contain
+// a keyword, so a content exclude without a type does not set it aside, and
+// no "content unreadable" warning is raised - while a real read failure (over
+// max-read) still fails closed (re-review N2, Łukasz's decision).
+func TestNoTextFormatIsNoMatch(t *testing.T) {
+	big := "confidential " + strings.Repeat("x", 2048)
+	h, dl := excludeTree(t, map[string]string{"photo.jpg": "\xff\xd8\xff\x00\x01binary", "big.txt": big})
+	main := writeConfig(t, h, `(include "dl")`, map[string]string{"dl": `
+(path "~/dl")
+(max-read 1K)
+(exclude (content "confidential"))
+(rule "pics" (when (type jpg)) (move "Pictures"))
+`})
+	e, errs := Load(main)
+	if len(errs) > 0 {
+		t.Fatal(errs)
+	}
+	r, err := e.Match(context.Background(), e.Dirs[0])
+	if err != nil {
+		t.Fatal(err)
+	}
+	for _, fm := range r.Matched {
+		switch fm.File.Rel {
+		case "photo.jpg":
+			if fm.Excluded != "" || len(fm.Rules) != 1 || len(fm.Warnings) != 0 {
+				t.Errorf("photo.jpg: Excluded %q, rules %d, warnings %v; want the pics rule and no warning", fm.Excluded, len(fm.Rules), fm.Warnings)
+			}
+		case "big.txt":
+			if !strings.HasSuffix(fm.Excluded, "(content unreadable)") {
+				t.Errorf("big.txt: Excluded %q; a real read failure must still fail closed", fm.Excluded)
+			}
+		}
+	}
+	x, err := e.Explain(context.Background(), filepath.Join(dl, "photo.jpg"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	if x.Excluded != "" {
+		t.Errorf("explain: Excluded %q, want none", x.Excluded)
+	}
+}
diff --git a/internal/engine/facts.go b/internal/engine/facts.go
index 487604b..ccdf18d 100644
--- a/internal/engine/facts.go
+++ b/internal/engine/facts.go
@@ -4,6 +4,7 @@ package engine
 
 import (
 	"context"
+	"errors"
 	"path/filepath"
 	"sort"
 	"strings"
@@ -178,7 +179,13 @@ func (f *facts) ContentContains(opt cond.Options, keywords []string) (int, error
 func (f *facts) extract(opt cond.Options, keywords []string) {
 	f.contentDone = true
 	text, err := f.run.e.Extract.Text(f.run.ctx, f.file.Path, f.file.Size, f.run.d.Settings.MaxRead)
-	if err != nil {
+	switch {
+	case errors.Is(err, extract.ErrUnsupported):
+		// A format with no text cannot contain a keyword: every answer is
+		// no, with no warning, and the answers are cached like any other
+		// (re-review N2). Only a real read failure is "unreadable".
+		text = ""
+	case err != nil:
 		f.contentErr = err
 		return
 	}
diff --git a/man/krino.conf.5 b/man/krino.conf.5
index 5153255..1fc113d 100644
--- a/man/krino.conf.5
+++ b/man/krino.conf.5
@@ -279,6 +279,8 @@ fails closed: when a content test it reaches cannot read the file
 the exclude holds and the file is set aside as
 .Dq (content unreadable) ,
 with a warning.
+A file whose format has no text at all, such as an image or an archive,
+is not unreadable: its content tests are false, with no warning.
 .Sh RULES
 .Bd -literal -offset indent
 (rule NAME ITEM...)
-- 
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