Write os::log messages to a file if possible

In order to allow for the output to `std{out,err}` to be as minimal as
possible without losing fidelity on our logs, we will make more use of
`os::log::debug` without setting `$OS_DEBUG`. Now, all logging functions
also try to write to a log file under `$LOG_DIR`, so we will be able to
inspect the log when looking for more verbose information.

Signed-off-by: Steve Kuznetsov <[email protected]>

Author: stevekuznetsov

hack/lib/log/output.sh

@@ -8,7 +8,9 @@
 # Arguments:
 #  - all: message to write
 function os::log::info() {
-	os::log::internal::prefix_lines "[INFO]" "$*"
+	local message; message="$( os::log::internal::prefix_lines "[INFO]" "$*" )"
+	os::log::internal::to_logfile "${message}"
+	echo "${message}"
 }
 readonly -f os::log::info
 
@@ -19,7 +21,9 @@ readonly -f os::log::info
 # Arguments:
 #  - all: message to write
 function os::log::warn() {
-	os::text::print_yellow "$( os::log::internal::prefix_lines "[WARNING]" "$*" )" 1>&2
+	local message; message="$( os::log::internal::prefix_lines "[WARNING]" "$*" )"
+	os::log::internal::to_logfile "${message}"
+	os::text::print_yellow "${message}" 1>&2
 }
 readonly -f os::log::warn
 
@@ -30,7 +34,9 @@ readonly -f os::log::warn
 # Arguments:
 #  - all: message to write
 function os::log::error() {
-	os::text::print_red "$( os::log::internal::prefix_lines "[ERROR]" "$*" )" 1>&2
+	local message; message="$( os::log::internal::prefix_lines "[ERROR]" "$*" )"
+	os::log::internal::to_logfile "${message}"
+	os::text::print_red "${message}" 1>&2
 }
 readonly -f os::log::error
 
@@ -42,23 +48,42 @@ readonly -f os::log::error
 # Arguments:
 #  - all: message to write
 function os::log::fatal() {
-	os::text::print_red "$( os::log::internal::prefix_lines "[FATAL]" "$*" )" 1>&2
+	local message; message="$( os::log::internal::prefix_lines "[FATAL]" "$*" )"
+	os::log::internal::to_logfile "${message}"
+	os::text::print_red "${message}" 1>&2
 	exit 1
 }
 readonly -f os::log::fatal
 
 # os::log::debug writes the message to stderr if
 # the ${OS_DEBUG} variable is set.
 #
+# Globals:
+#  - OS_DEBUG
 # Arguments:
 #  - all: message to write
 function os::log::debug() {
+	local message; message="$( os::log::internal::prefix_lines "[DEBUG]" "$*" )"
+	os::log::internal::to_logfile "${message}"
 	if [[ -n "${OS_DEBUG:-}" ]]; then
-		os::text::print_blue "$( os::log::internal::prefix_lines "[DEBUG]" "$*" )" 1>&2
+		os::text::print_blue "${message}" 1>&2
 	fi
 }
 readonly -f os::log::debug
 
+# os::log::internal::to_logfile makes a best-effort
+# attempt to write the message to the script logfile
+#
+# Globals:
+#  - LOG_DIR
+# Arguments:
+#  - all: message to write
+function os::log::internal::to_logfile() {
+	if [[ -n "${LOG_DIR:-}" ]]; then
+		echo "$*" >>"${LOG_DIR}/scripts.log"
+	fi
+}
+
 # os::log::internal::prefix_lines prints out the
 # original content with the given prefix at the
 # start of every line.