Yann Autissier
55fae625d6
Two mechanisms, matching what the make engine actually did:
Lazy defaults. A stack setting is a function myos_default_<VAR>, called only
when the variable has no value, and called again at every reference. That is
exactly a recursive ?=: an explicit value wins, and the default follows a
DOMAIN that a .env changes later. The prefix is what makes it safe; the first
version used a bare function named after the variable, and the test suite
caught it running /usr/bin/host for a stack group called host.
Templates. myos env-update fills a .env from the .env.dist files, expanding
${VAR} against the current values and running $(command), forward references
included.
Also fixed: the project .env now wins over /etc/conf.d/myos, which is what the
documentation claimed and the code did not.
share/make/shim.mk lets a project keep make as a front end: every myos command
becomes a target that shells out to bin/myos, and the project keeps its own
targets and its stack .mk files. It sits outside make/ because the legacy
engine globs every .mk in there.
57 lines
2.0 KiB
Bash
57 lines
2.0 KiB
Bash
#shellcheck shell=sh
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# var: variable resolution, with the lazy defaults the make engine had.
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#
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# make gives every `VAR ?= $(call ...)` two properties at once: an explicit
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# value wins, and the default is re-evaluated at each reference, so it sees
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# whatever a .env loaded later has changed.
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#
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# The shell gets both by keeping defaults in functions: `myos_var NAME` reads
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# the variable when it has a value, and otherwise calls the function
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# `myos_default_NAME`. The prefix matters: a bare function named after the
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# variable would collide with commands on PATH, and a stack setting called
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# `host` or `test` would then run a program instead of returning a value.
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#
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# myos_default_HOST_FABIO_SERVICE_9998_TAGS() { myos_tagprefix HOST_FABIO 9998; }
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#
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# is the exact equivalent of
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#
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# HOST_FABIO_SERVICE_9998_TAGS ?= $(call tagprefix,HOST_FABIO,9998)
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MYOS_VAR_MAX_DEPTH=${MYOS_VAR_MAX_DEPTH:-32}
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# myos_var NAME the value of NAME: the variable if it has one, else the lazy
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# default, else empty.
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myos_var() {
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[ -n "${1:-}" ] || return 0
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eval "_myos_set=\${$1+yes}"
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if [ "${_myos_set:-}" = yes ]; then
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eval "printf '%s' \"\$$1\""
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return 0
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fi
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myos_var_is_lazy "$1" || return 0
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# a default written in terms of itself would loop for ever
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_myos_depth=$((${MYOS_VAR_DEPTH:-0} + 1))
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if [ "$_myos_depth" -gt "$MYOS_VAR_MAX_DEPTH" ]; then
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myos_error "variable $1 is defined in terms of itself"
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return 1
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fi
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MYOS_VAR_DEPTH=$_myos_depth "myos_default_$1"
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}
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# myos_default NAME BODY declare a lazy default from a string, for callers
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# that build the variable name at run time
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myos_default() {
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eval "myos_default_$1() { $2; }"
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}
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# myos_var_is_lazy NAME true when NAME has no value but has a lazy default
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myos_var_is_lazy() {
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eval "_myos_set=\${$1+yes}"
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[ "${_myos_set:-}" = yes ] && return 1
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# a shell function, never a command on PATH: command -v prints the name back
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# for a function and a path for a program
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_myos_fn=$(command -v "myos_default_$1" 2>/dev/null) || return 1
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[ "$_myos_fn" = "myos_default_$1" ]
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}
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