engine: resources, lang: Set resource fields more accurately

There were some bugs about setting resource fields that were structs
with various fields. This makes things more strict and correct. Now we
check for duplicate field names earlier (duplicates due to identical
aliases) and we also don't try and set private fields, or incorrectly
set partial structs.

Most interestingly, this also cleans up all of the resources and ensures
that each one has nicer docs and a clear struct tag for fields that we
want to use in mcl. These are mandatory now, and if you're missing the
tag, then we will ignore the field.

engine/resources/exec.go

@@ -49,51 +49,61 @@ type ExecRes struct {
 	init *engine.Init
 
 	// Cmd is the command to run. If this is not specified, we use the name.
-	Cmd string `yaml:"cmd"`
+	Cmd string `lang:"cmd" yaml:"cmd"`
+
 	// Args is a list of args to pass to Cmd. This can be used *instead* of
 	// passing the full command and args as a single string to Cmd. It can
 	// only be used when a Shell is *not* specified. The advantage of this
 	// is that you don't have to worry about escape characters.
-	Args []string `yaml:"args"`
+	Args []string `lang:"args" yaml:"args"`
+
 	// Cwd is the dir to run the command in. If empty, then this will use
 	// the working directory of the calling process. (This process is mgmt,
 	// not the process being run here.)
-	Cwd string `yaml:"cwd"`
+	Cwd string `lang:"cwd" yaml:"cwd"`
+
 	// Shell is the (optional) shell to use to run the cmd. If you specify
 	// this, then you can't use the Args parameter.
-	Shell string `yaml:"shell"`
+	Shell string `lang:"shell" yaml:"shell"`
+
 	// Timeout is the number of seconds to wait before sending a Kill to the
 	// running command. If the Kill is received before the process exits,
 	// then this be treated as an error.
-	Timeout uint64 `yaml:"timeout"`
+	Timeout uint64 `lang:"timeout" yaml:"timeout"`
+
 	// Env allows the user to specify environment variables for script
 	// execution. These are taken using a map of format of VAR_NAME -> value.
-	Env map[string]string `yaml:"env"`
+	Env map[string]string `lang:"env" yaml:"env"`
 
-	// Watch is the command to run to detect event changes. Each line of
+	// WatchCmd is the command to run to detect event changes. Each line of
 	// output from this command is treated as an event.
-	WatchCmd string `yaml:"watchcmd"`
+	WatchCmd string `lang:"watchcmd" yaml:"watchcmd"`
+
 	// WatchCwd is the Cwd for the WatchCmd. See the docs for Cwd.
-	WatchCwd string `yaml:"watchcwd"`
+	WatchCwd string `lang:"watchcwd" yaml:"watchcwd"`
+
 	// WatchShell is the Shell for the WatchCmd. See the docs for Shell.
-	WatchShell string `yaml:"watchshell"`
+	WatchShell string `lang:"watchshell" yaml:"watchshell"`
 
 	// IfCmd is the command that runs to guard against running the Cmd. If
 	// this command succeeds, then Cmd *will* be run. If this command
 	// returns a non-zero result, then the Cmd will not be run. Any error
 	// scenario or timeout will cause the resource to error.
-	IfCmd string `yaml:"ifcmd"`
+	IfCmd string `lang:"ifcmd" yaml:"ifcmd"`
+
 	// IfCwd is the Cwd for the IfCmd. See the docs for Cwd.
-	IfCwd string `yaml:"ifcwd"`
+	IfCwd string `lang:"ifcwd" yaml:"ifcwd"`
+
 	// IfShell is the Shell for the IfCmd. See the docs for Shell.
-	IfShell string `yaml:"ifshell"`
+	IfShell string `lang:"ifshell" yaml:"ifshell"`
 
 	// User is the (optional) user to use to execute the command. It is used
 	// for any command being run.
-	User string `yaml:"user"`
+	User string `lang:"user" yaml:"user"`
+
 	// Group is the (optional) group to use to execute the command. It is
 	// used for any command being run.
-	Group string `yaml:"group"`
+	Group string `lang:"group" yaml:"group"`
 
 	output *string // all cmd output, read only, do not set!
 	stdout *string // the cmd stdout, read only, do not set!