Documentation
¶
Overview ¶
Package pkg is the collection of packages that make up the implementation of ytt.
This codebase is intentionally organized into well-defined layers. A concerted effort has been sustained to keep the responsibility of each package concise and complete. Packages have been designed to be dependent on each other only to the degree absolutely required.
In the inventory, below, individual packages are named alongside their coupling with the other packages in the codebase.
(# of dependents) => <package name> => (# of dependencies)
Where "# of dependents" is the count of packages that import the named package and "# of dependencies" is the count of packages that this named package imports.
This is output from the tool https://github.com/jtigger/go-orient.
From top-down (http://www.catb.org/~esr/writings/taoup/html/ch04s03.html), ytt code is layered in this way:
Entry Point ¶
ytt is built into two executable formats:
./cmd/ytt // a command-line tool ./cmd/ytt-lambda-website // an AWS Lambda function
ytt's contains a mini website that is the "Playground".
(1) => pkg/website => (0)
Commands ¶
There are half-a-dozen commands ytt implements. The most commonly used and most complex is "template".
(1) => pkg/cmd => (8) (2) => pkg/cmd/template => (10)
The Workspace ¶
ytt processing can be thought of as a sequence of steps: schema "pre-processing", data values "pre-processing", template evaluation, and overlay "post-processing". All of these steps are executed over a collection of files we call a workspace.Library.
(1) => pkg/workspace => (14) (2) => pkg/workspace/datavalues => (6) (3) => pkg/workspace/ref => (2) (4) => pkg/files => (1) (10) => pkg/filepos => (0)
Templating ¶
The heart of ytt's action is structural templating. There are two flavors of templates: templating on a YAML structure and templating on text. Each source template file is "compiled" into a Starlark program whose job is to build-up the output.
(9) => pkg/template => (2) (9) => pkg/template/core => (1) (3) => pkg/yamltemplate => (6) (2) => pkg/texttemplate => (2)
Standard Library ¶
ytt injects a collection of "standard" modules into Starlark executions. These modules support serialization, hashing, parsing of special kinds of values, and programmatic access to some of ytt's core capabilities. This collection is known as a library (not to be confused with the workspace.Library concept).
(2) => pkg/yttlibrary => (5)
The implementation for ytt's other fundamental feature -- Overlays -- lives within this standard library. This allows for both template authors and ytt itself to use this powerful editing feature.
(3) => pkg/yttlibrary/overlay => (5)
"Standard Library" modules that have Go dependencies are included as "extensions" to minimize the set of transitive dependencies that come from the github.com/vmware-tanzu/carvel-ytt module.
(1) => pkg/yttlibraryext => (1) (1) => pkg/yttlibraryext/toml => (4)
YAML Enhancements ¶
ytt can enrich a YAML structure with more fine-grained data typing and user-defined constraints on values.
(3) => pkg/schema => (5) (1) => pkg/assertions => (5)
YAML Structures ¶
At the heart of ytt is the ability to parse annotated YAML.
ytt delegates parsing YAML to the de facto standard YAML library (https://github.com/go-yaml/yaml/tree/v2). However, ytt needs to store additional information about nodes (e.g. templating, type info, processing hints, etc.). It does this by converting the output from the standard YAML parser into a composite tree of its own yamlmeta.Node structure that can hold that metadata.
(11) => pkg/yamlmeta => (3) (1) => pkg/yamlmeta/internal/yaml.v2 => (0)
Utilities ¶
Finally, there is a collection of supporting features.
One of which provides the implementation of the "fmt" command:
(1) => pkg/yamlfmt => (1)
The remainder are domain-agnostic utilities that provide either an application-level capability or a specialized piece of logic.
(5) => pkg/cmd/ui => (0) (5) => pkg/orderedmap => (0) (2) => pkg/version => (0) (2) => pkg/feature => (0) (1) => pkg/spell => (0)
Dependencies ¶
Each package's dependencies on other packages within this module are as follows (if a package is not listed, it has no dependencies on other packages within this module):
pkg/cmd/template: - pkg/workspace - pkg/workspace/datavalues - pkg/schema - pkg/workspace/ref - pkg/yttlibrary/overlay - pkg/files - pkg/cmd/ui - pkg/template - pkg/filepos - pkg/yamlmeta pkg/workspace: - pkg/assertions - pkg/texttemplate - pkg/workspace/datavalues - pkg/yttlibrary - pkg/schema - pkg/workspace/ref - pkg/yamltemplate - pkg/yttlibrary/overlay - pkg/files - pkg/cmd/ui - pkg/template - pkg/template/core - pkg/filepos - pkg/yamlmeta pkg/assertions: - pkg/feature - pkg/yamltemplate - pkg/template - pkg/filepos - pkg/yamlmeta pkg/yamltemplate: - pkg/texttemplate - pkg/orderedmap - pkg/template - pkg/template/core - pkg/filepos - pkg/yamlmeta pkg/texttemplate: - pkg/template - pkg/filepos pkg/template: - pkg/template/core - pkg/filepos pkg/template/core: - pkg/orderedmap pkg/yamlmeta: - pkg/yamlmeta/internal/yaml.v2 - pkg/orderedmap - pkg/filepos pkg/workspace/datavalues: - pkg/schema - pkg/workspace/ref - pkg/template - pkg/template/core - pkg/filepos - pkg/yamlmeta pkg/schema: - pkg/spell - pkg/template - pkg/template/core - pkg/filepos - pkg/yamlmeta pkg/workspace/ref: - pkg/template - pkg/template/core pkg/yttlibrary: - pkg/version - pkg/yttlibrary/overlay - pkg/orderedmap - pkg/template/core - pkg/yamlmeta pkg/yttlibrary/overlay: - pkg/yamltemplate - pkg/template - pkg/template/core - pkg/filepos - pkg/yamlmeta pkg/files: - pkg/cmd/ui pkg/cmd: - pkg/website - pkg/yamlfmt - pkg/yttlibraryext - pkg/cmd/template - pkg/version - pkg/files - pkg/cmd/ui - pkg/yamlmeta pkg/yamlfmt: - pkg/yamlmeta pkg/yttlibraryext: - pkg/yttlibraryext/toml pkg/yttlibraryext/toml: - pkg/yttlibrary - pkg/orderedmap - pkg/template/core - pkg/yamlmeta
Source Files
Directories
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| Path | Synopsis |
|---|---|
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Package cmd is home to the full set of ytt's "commands" -- instances of cobra.Command (not to be confused with ./cmd which contains the bootstrapping for executing ytt in various environments).
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Package cmd is home to the full set of ytt's "commands" -- instances of cobra.Command (not to be confused with ./cmd which contains the bootstrapping for executing ytt in various environments). |
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template
Package template implements the "template" command (not to be confused with "pkg/template" home of the templating mechanism itself).
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Package template implements the "template" command (not to be confused with "pkg/template" home of the templating mechanism itself). |
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ui
Package ui provides a thin abstraction over user input and output (typically, a tty device).
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Package ui provides a thin abstraction over user input and output (typically, a tty device). |
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Package experiments provides a global "Feature Flag" facility for circuit-breaking pre-GA code.
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Package experiments provides a global "Feature Flag" facility for circuit-breaking pre-GA code. |
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Package filepos provides the concept of Position: a source name (usually a file) and line number within that source.
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Package filepos provides the concept of Position: a source name (usually a file) and line number within that source. |
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Package files provides primitives for enumerating and loading data from various file or file-like Source's and for writing output to filesystem files and directories.
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Package files provides primitives for enumerating and loading data from various file or file-like Source's and for writing output to filesystem files and directories. |
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Package orderedmap provides a map implementation where the order of keys is maintained (unlike the native Go map).
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Package orderedmap provides a map implementation where the order of keys is maintained (unlike the native Go map). |
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Package schema enhances yamlmeta.Node structures with fine-grain data types.
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Package schema enhances yamlmeta.Node structures with fine-grain data types. |
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Package spell provides the ability to suggest an exact spelling of a word.
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Package spell provides the ability to suggest an exact spelling of a word. |
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Package template provides the core templating engine for ytt.
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Package template provides the core templating engine for ytt. |
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core
Package core provides facilities for low-level integration with Starlark.
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Package core provides facilities for low-level integration with Starlark. |
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Package texttemplate implements the text dialect of the ytt templating engine.
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Package texttemplate implements the text dialect of the ytt templating engine. |
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Package validations enriches YAML structures by attaching user-defined constraints (that is, validationRun rules) onto individual yamlmeta.Node's.
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Package validations enriches YAML structures by attaching user-defined constraints (that is, validationRun rules) onto individual yamlmeta.Node's. |
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Package version is where the version of the ytt binary is set.
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Package version is where the version of the ytt binary is set. |
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Package website provides the web-based Playground via an HTTP webserver.
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Package website provides the web-based Playground via an HTTP webserver. |
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Package workspace is home to primitives for loading and processing ytt artifacts including the core four steps: pre-processing schema and data values, evaluating templates, and post-processing overlays.
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Package workspace is home to primitives for loading and processing ytt artifacts including the core four steps: pre-processing schema and data values, evaluating templates, and post-processing overlays. |
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datavalues
Package datavalues integrates the schema and data values features into the workspace, providing a means of "addressing" to specific libraries.
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Package datavalues integrates the schema and data values features into the workspace, providing a means of "addressing" to specific libraries. |
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ref
Package ref provides the general-purpose ability to mark a document as targeted for specific library.
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Package ref provides the general-purpose ability to mark a document as targeted for specific library. |
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Package yamlfmt implements the "fmt" command — formatting YAML (preserving comments) into a canonical form.
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Package yamlfmt implements the "fmt" command — formatting YAML (preserving comments) into a canonical form. |
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Package yamlmeta parses YAML streams into a data structure (tree of yamlmeta.Node's) on which comments and metadata can be attached.
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Package yamlmeta parses YAML streams into a data structure (tree of yamlmeta.Node's) on which comments and metadata can be attached. |
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internal/yaml.v2
Package yaml implements YAML support for the Go language.
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Package yaml implements YAML support for the Go language. |
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Package yamltemplate implements the YAML dialect of the ytt templating engine.
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Package yamltemplate implements the YAML dialect of the ytt templating engine. |
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Package yttlibrary implements the "Standard Library" of modules that are built-in to the ytt templating engine.
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Package yttlibrary implements the "Standard Library" of modules that are built-in to the ytt templating engine. |
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overlay
Package overlay implements YAML patching via ytt annotations.
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Package overlay implements YAML patching via ytt annotations. |
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Package yttlibraryext contains "Standard Library" modules that involve Go module dependencies and therefore are optional or extensions.
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Package yttlibraryext contains "Standard Library" modules that involve Go module dependencies and therefore are optional or extensions. |
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toml
Package toml extends the ytt "Standard Library" with the ability to encode and decode text in TOML format.
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Package toml extends the ytt "Standard Library" with the ability to encode and decode text in TOML format. |