Add tests for pager library

lib/pager.sh

@@ -18,23 +18,18 @@ is_pager_disabled() {
 	return $?
 }
 
-# Gets the name of the pager command.
+# Prints the detected pager name.
 pager_name() {
-	if [[ -z "${SCRIPT_PAGER_CMD[0]}" ]]; then return; fi
-	if [[ -z "$_SCRIPT_PAGER_NAME" ]]; then
-		local output
-		output="$("${SCRIPT_PAGER_CMD[0]}" --version 2>&1)"
-
-		if head -n 1 <<<"$output" | grep '^less \d' &>/dev/null; then
-			_SCRIPT_PAGER_NAME="less"
-		else
-			_SCRIPT_PAGER_NAME="$(basename "${SCRIPT_PAGER_CMD[0]}")"
-		fi
-	fi
-
+	_detect_pager
 	echo "$_SCRIPT_PAGER_NAME"
 }
 
+# Prints the detected pager version.
+pager_version() {
+	_detect_pager
+	echo "$_SCRIPT_PAGER_VERSION"
+}
+
 # Executes a command or function, and pipes its output to the pager (if it exists).
 #
 # Returns: The exit code of the command.
@@ -66,25 +61,70 @@ pager_display() {
 
 # -----------------------------------------------------------------------------
 
-# Defaults.
-SCRIPT_PAGER_CMD=("$PAGER")
-SCRIPT_PAGER_ARGS=()
+# Detect the pager information.
+# shellcheck disable=SC2120
+_detect_pager() {
+	if [[ "$_SCRIPT_PAGER_DETECTED" = "true" && "$1" != "--force" ]]; then return; fi
+	_SCRIPT_PAGER_DETECTED=true
 
-# Add arguments for the less pager.
-if is_pager_less; then
-	SCRIPT_PAGER_ARGS=(-R)
-fi
+	# If the pager command is empty, the pager is disabled.
+	if [[ -z "${SCRIPT_PAGER_CMD[0]}" ]]; then
+		_SCRIPT_PAGER_VERSION=0
+		_SCRIPT_PAGER_NAME=""
+		return;
+	fi
 
-# Prefer the bat pager.
-if [[ -n "${BAT_PAGER+x}" ]]; then
-	# [note]: This is intentional.
-	# shellcheck disable=SC2206
-	SCRIPT_PAGER_CMD=($BAT_PAGER)
+	# Determine the pager name and version.
+	local output
+	local output1
+	output="$("${SCRIPT_PAGER_CMD[0]}" --version 2>&1)"
+	output1="$(head -n 1 <<<"$output")"
+
+	if [[ "$output1" =~ ^less[[:blank:]]([[:digit:]]+) ]]; then
+		# shellcheck disable=SC2001
+		_SCRIPT_PAGER_VERSION="${BASH_REMATCH[1]}"
+		_SCRIPT_PAGER_NAME="less"
+	else
+		_SCRIPT_PAGER_VERSION=0
+		_SCRIPT_PAGER_NAME="$(basename "${SCRIPT_PAGER_CMD[0]}")"
+	fi
+}
+
+# Configure the script pager.
+# This attempts to mimic how bat determines the pager and pager arguments.
+#
+# 1. Use BAT_PAGER
+# 2. Use PAGER with special arguments for less
+# 3. Use PAGER
+_configure_pager() {
+	SCRIPT_PAGER_CMD=("$PAGER")
 	SCRIPT_PAGER_ARGS=()
-fi
 
-# Prefer no pager if not a tty.
-if ! [[ -t 1 ]]; then
+	# Prefer the bat pager.
+	if [[ -n "${BAT_PAGER+x}" ]]; then
+		# [note]: This is intentional.
+		# shellcheck disable=SC2206
+		SCRIPT_PAGER_CMD=($BAT_PAGER)
+		SCRIPT_PAGER_ARGS=()
+		return
+	fi
+
+	# Add arguments for the less pager.
+	if is_pager_less; then
+		SCRIPT_PAGER_ARGS=(-R --quit-if-one-screen)
+		if [[ "$(pager_version)" -lt 500 ]]; then
+			SCRIPT_PAGER_ARGS+=(--no-init)
+		fi
+	fi
+}
+
+# -----------------------------------------------------------------------------
+
+if [[ -t 1 ]]; then
+	# Detect and choose the arguments for the pager.
+	_configure_pager
+else
+	# Prefer no pager if not a tty.
 	SCRIPT_PAGER_CMD=()
 	SCRIPT_PAGER_ARGS=()
 fi

test/shimexec/less

@@ -0,0 +1,15 @@
+#!/usr/bin/env bash
+if [[ "$1" = "--version" ]]; then
+cat <<EOF
+less ${MOCK_LESS_VERSION:-551} (PCRE regular expressions)
+Copyright (C) 1984-2019  Mark Nudelman
+
+less comes with NO WARRANTY, to the extent permitted by law.
+For information about the terms of redistribution,
+see the file named README in the less distribution.
+Home page: http://www.greenwoodsoftware.com/less
+EOF
+exit 0
+fi
+
+cat "$1"

test/shimexec/less_but_renamed

@@ -0,0 +1,2 @@
+#!/usr/bin/env bash
+exec less "$@"

test/shimexec/not_less

@@ -0,0 +1,10 @@
+#!/usr/bin/env bash
+if [[ "$1" = "--version" ]]; then
+cat <<EOF
+not less ${MOCK_LESS_VERSION:-551} (PCRE regular expressions)
+:(
+EOF
+exit 0
+fi
+
+cat "$1"

test/suite/lib_pager.sh

@@ -0,0 +1,74 @@
+setup() {
+	source "${LIB}/pager.sh"
+}
+
+use_pager() {
+	unset BAT_PAGER
+	export PAGER="$1"
+
+	SCRIPT_PAGER_CMD=("$PAGER")
+	SCRIPT_PAGER_ARGS=()
+
+	_detect_pager --force
+	_configure_pager
+}
+
+use_bat_pager() {
+	unset PAGER
+	export BAT_PAGER="$1"
+
+	SCRIPT_PAGER_CMD=($BAT_PAGER)
+	SCRIPT_PAGER_ARGS=()
+
+	_detect_pager --force
+	_configure_pager
+}
+
+test:less_detection() {
+	description "Identify less"
+
+	use_pager "less"             && expect_equal "$(pager_name)" "less"
+	use_pager "less_but_renamed" && expect_equal "$(pager_name)" "less"
+	use_pager "tput"             && expect_equal "$(pager_name)" "tput"
+}
+
+test:less_version() {
+	description "Identify less version"
+
+	export MOCK_LESS_VERSION=473
+	use_pager "less" && expect_equal "$(pager_version)" "473"
+
+	export MOCK_LESS_VERSION=551
+	use_pager "less" && expect_equal "$(pager_version)" "551"
+}
+
+test:less_args() {
+	description "Automatically select appropriate less args"
+
+	export MOCK_LESS_VERSION=473
+	use_pager "less"
+	expect array_contains "-R" in "${SCRIPT_PAGER_ARGS[@]}"
+	expect array_contains "--quit-if-one-screen" in "${SCRIPT_PAGER_ARGS[@]}"
+	expect array_contains "--no-init" in "${SCRIPT_PAGER_ARGS[@]}"
+
+	export MOCK_LESS_VERSION=551
+	use_pager "less"
+	expect array_contains "-R" in "${SCRIPT_PAGER_ARGS[@]}"
+	expect array_contains "--quit-if-one-screen" in "${SCRIPT_PAGER_ARGS[@]}"
+	expect ! array_contains "--no-init" in "${SCRIPT_PAGER_ARGS[@]}"
+
+	use_pager "not_less"
+	expect_equal "${#SCRIPT_PAGER_ARGS[@]}" 0
+}
+
+test:env_bat_pager() {
+	description "Check that BAT_PAGER is being used"
+
+	use_bat_pager "not_less"
+	expect_equal "$SCRIPT_PAGER_CMD" "not_less"
+
+	use_bat_pager "not_less but not_more"
+	expect_equal "$SCRIPT_PAGER_CMD" "not_less"
+	expect_equal "${SCRIPT_PAGER_CMD[1]}" "but"
+	expect_equal "${SCRIPT_PAGER_CMD[2]}" "not_more"
+}