b57e4c4414
This change introduces the notion of "Stack subclassing" in two ways:
1. A Stack may declare that it subclasses another one using the base property:
name: mystack
base: other/stack
.. as before ..
2. A Stack may declare that it is abstract; in other words, that it is meant
solely for subclassing, and cannot be compiled and deployed independently:
name: mystack
abstract: true
.. as before ..
Note that non-abstract Stacks are required to declare at least one Service,
whether that is public, private, or both.
128 lines
6.2 KiB
Go
128 lines
6.2 KiB
Go
// Copyright 2016 Marapongo, Inc. All rights reserved.
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// This package contains the core Mu abstract syntax tree types.
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//
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// N.B. for the time being, we are leveraging the same set of types for parse trees and abstract syntax trees. The
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// reason is that minimal "extra" information is necessary between front- and back-end parts of the compiler, and so
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// reusing the trees leads to less duplication in types and faster runtime performance. As the compiler matures in
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// functionality, we may want to revisit this. The "back-end-only" parts of the data structures are easily identified
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// because their fields do not map to any serializable fields (i.e., `json:"-"`).
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//
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// Another controversial decision is to mutate nodes in place, rather than taking the performance hit of immutability.
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// This can certainly be tricky to deal with, however, it is simpler and we can revisit it down the road if needed.
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// Of course, during lowering, sometimes nodes will be transformed to new types entirely, allocating entirely anew.
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package ast
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// Name is an identifier. Names may be optionally fully qualified, using the delimiter `/`, or simple. Each element
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// conforms to the regex [A-Za-z_][A-Za-z0-9_]*. For example, `marapongo/mu/stack`.
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type Name string
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// SemVer represents a version using "semantic versioning" style. This may include up to three distinct numbers
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// delimited by `.`s: a major version number, a minor version number, and a revision number. For example, `1.0.10`.
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type SemVer string
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// Node is the base of all abstract syntax tree types.
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type Node struct {
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}
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// Metadata contains human-readable metadata common to Mu's packaging formats (like Stacks and Clusters).
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type Metadata struct {
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Node
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Kind string `json:"-"` // kind is decorated post-parsing, since it is contextual.
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Name Name `json:"name,omitempty"` // a friendly name for this node.
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Version SemVer `json:"version,omitempty"` // a specific semantic version.
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Description string `json:"description,omitempty"` // an optional friendly description.
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Author string `json:"author,omitempty"` // an optional author.
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Website string `json:"website,omitempty"` // an optional website for additional info.
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License string `json:"license,omitempty"` // an optional license governing legal uses of this package.
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Targets Targets `json:"targets,omitempty"` // an optional set of predefined target cloud environments.
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}
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// Targets is a map of target names to metadata about those targets.
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type Targets map[string]Target
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// Target describes a predefined cloud runtime target, including its OS and Scheduler combination.
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type Target struct {
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Node
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Name string `json:"-"` // name is decorated post-parsing, since it is contextual.
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Default bool `json:"default,omitempty"` // a single target can carry default settings.
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Description string `json:"description,omitempty"` // a human-friendly description of this target.
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Cloud string `json:"cloud,omitempty"` // the cloud target.
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Scheduler string `json:"scheduler,omitempty"` // the cloud scheduler target.
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Options map[string]interface{} `json:"options,omitempty"` // any options passed to the cloud provider.
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}
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// Cluster describes a cluster of many Stacks, in addition to other metadata, like predefined Targets.
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type Cluster struct {
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Metadata
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}
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// Stack represents a collection of private and public cloud resources, a method for constructing them, and optional
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// dependencies on other Stacks (by name).
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type Stack struct {
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Metadata
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Base Name `json:"base,omitempty"` // an optional base Stack type.
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Abstract bool `json:"abstract,omitempty"` // true if this stack is "abstract" (uninstantiable).
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Parameters Parameters `json:"parameters,omitempty"`
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Dependencies Dependencies `json:"dependencies,omitempty"`
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Services Services `json:"services,omitempty"`
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BoundBase *Stack `json:"-"` // base, if available, is bound during semantic analysis.
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BoundDependencies BoundDependencies `json:"-"` // dependencies are bound during semantic analysis.
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}
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// Parameters maps parameter names to metadata about those parameters.
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type Parameters map[string]Parameter
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// Parameter describes the requirements of arguments used when constructing Stacks, etc.
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type Parameter struct {
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Node
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Name string `json:"-"` // name is decorated post-parsing, since it is contextual.
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Type Name `json:"type,omitempty"` // the type of the parameter; required.
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Description string `json:"description,omitempty"` // an optional friendly description of the parameter.
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Default interface{} `json:"default,omitempty"` // an optional default value if the caller doesn't pass one.
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Optional bool `json:"optional,omitempty"` // true if may be omitted (inferred if a default value).
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}
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// Dependencies maps dependency names to the semantic version the consumer depends on.
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type Dependencies map[Name]Dependency
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// Dependency is metadata describing a dependency target (for now, just its semantic version).
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type Dependency SemVer
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// BoundDependencies contains a map of all bound dependencies, populated during semantic analysis.
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type BoundDependencies map[Name]*Stack
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// Services is a list of public and private service references, keyed by name.
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type Services struct {
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Public ServiceMap `json:"public,omitempty"`
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Private ServiceMap `json:"private,omitempty"`
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}
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// ServiceMap is a map of service names to metadata about those services.
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type ServiceMap map[Name]Service
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// Service is a directive for instantiating another Stack, including its name, arguments, etc.
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type Service struct {
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Node
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Name Name `json:"-"` // a friendly name; decorated post-parsing, since it is contextual.
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Public bool `json:"-"` // true if this service is publicly exposed; also decorated post-parsing.
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Type Name `json:"type,omitempty"` // an explicit type; if missing, the name is used.
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// TODO: Service metadata is highly type-dependent. It's not yet clear how best to represent this in the schema.
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}
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// TODO: several more core types still need to be mapped:
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// - Schema
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// - Identity: User, Role, Group
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// - Configuration
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// - Secret
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