1 file changed, 43 insertions, 0 deletions
diff --git a/tests/extensions/test-syntax-highlight.lua b/tests/extensions/test-syntax-highlight.lua
index d8e5224..90ef5b9 100644
--- a/tests/extensions/test-syntax-highlight.lua
+++ b/tests/extensions/test-syntax-highlight.lua
@@ -66,6 +66,46 @@ if mode == "nolexers" then
 	h.equals("and the error log says none were found", h.error_log(),
 		"[cgit] Unable to find the Scintillua lexers, so source is shown uncoloured\n")
 
+	-- The filter takes a module called lexer only when it is Scintillua, so
+	-- one that is something else is never used. A Scintillua older than 6.0
+	-- has no detect() and colours nothing, and lexers that need a missing
+	-- lpeg say why in the log. Each loads the filter afresh with the module
+	-- it finds forced through package.preload.
+	local function load_with_lexer(loader)
+		package.loaded.lexer = nil
+		package.preload.lexer = loader
+		h.setenv("CGIT_SCINTILLUA_PATH", "/nonexistent")
+		h.load(script)
+	end
+
+	local used = false
+	load_with_lexer(function()
+		return { detect = function() used = true end }
+	end)
+	out = render("hello.fake", "a <b>")
+	h.equals("a lexer module without load is passed over", out, "a &lt;b&gt;")
+	h.check("and never used", not used)
+	h.equals("and the error log stays empty", h.error_log(), "")
+
+	load_with_lexer(function()
+		return { load = function() return { lex = function() return { "keyword", 2 } end } end }
+	end)
+	out = render("hello.fake", "a <b>")
+	h.equals("a Scintillua without detect colours nothing", out, "a &lt;b&gt;")
+	h.equals("and logs nothing", h.error_log(), "")
+
+	h.preload_failure("lpeg")
+	load_with_lexer(function()
+		return require("lpeg")
+	end)
+	out = render("hello.fake", "a <b>")
+	h.equals("lexers that cannot load lpeg leave the source uncoloured", out, "a &lt;b&gt;")
+	local log = h.error_log()
+	local prefix = "[cgit] Unable to load the Scintillua lexers: "
+	h.equals("and the error log says why", log:sub(1, #prefix), prefix)
+	h.contains("naming lpeg", log, "lpeg deliberately unavailable")
+	h.equals("on one line", log:find("\n", 1, true), #log)
+
 	h.finish()
 end
 
@@ -96,6 +136,9 @@ h.equals("a lexer stopping early leaves an escaped tail", out, "<span class='hl-
 out = render("boom.badlex", "some <code>")
 h.equals("a lexer that raises falls back to escaped text", out, "some &lt;code&gt;")
 
+out = render("empty.nothing", "some <code>")
+h.equals("a lexer that returns no tokens falls back to escaped text", out, "some &lt;code&gt;")
+
 out = render("HELLO.FAKE", "if 42")
 h.contains("an extension in capitals finds its lexer", out,
 	"<span class='hl-keyword'>if</span>")