summaryrefslogtreecommitdiff
path: root/vendor/golang.org/x/text/message/catalog/catalog.go
diff options
context:
space:
mode:
Diffstat (limited to 'vendor/golang.org/x/text/message/catalog/catalog.go')
-rw-r--r--vendor/golang.org/x/text/message/catalog/catalog.go369
1 files changed, 369 insertions, 0 deletions
diff --git a/vendor/golang.org/x/text/message/catalog/catalog.go b/vendor/golang.org/x/text/message/catalog/catalog.go
new file mode 100644
index 0000000..34a30d3
--- /dev/null
+++ b/vendor/golang.org/x/text/message/catalog/catalog.go
@@ -0,0 +1,369 @@
+// Copyright 2017 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package catalog defines collections of translated format strings.
+//
+// This package mostly defines types for populating catalogs with messages. The
+// catmsg package contains further definitions for creating custom message and
+// dictionary types as well as packages that use Catalogs.
+//
+// Package catalog defines various interfaces: Dictionary, Loader, and Message.
+// A Dictionary maintains a set of translations of format strings for a single
+// language. The Loader interface defines a source of dictionaries. A
+// translation of a format string is represented by a Message.
+//
+//
+// Catalogs
+//
+// A Catalog defines a programmatic interface for setting message translations.
+// It maintains a set of per-language dictionaries with translations for a set
+// of keys. For message translation to function properly, a translation should
+// be defined for each key for each supported language. A dictionary may be
+// underspecified, though, if there is a parent language that already defines
+// the key. For example, a Dictionary for "en-GB" could leave out entries that
+// are identical to those in a dictionary for "en".
+//
+//
+// Messages
+//
+// A Message is a format string which varies on the value of substitution
+// variables. For instance, to indicate the number of results one could want "no
+// results" if there are none, "1 result" if there is 1, and "%d results" for
+// any other number. Catalog is agnostic to the kind of format strings that are
+// used: for instance, messages can follow either the printf-style substitution
+// from package fmt or use templates.
+//
+// A Message does not substitute arguments in the format string. This job is
+// reserved for packages that render strings, such as message, that use Catalogs
+// to selected string. This separation of concerns allows Catalog to be used to
+// store any kind of formatting strings.
+//
+//
+// Selecting messages based on linguistic features of substitution arguments
+//
+// Messages may vary based on any linguistic features of the argument values.
+// The most common one is plural form, but others exist.
+//
+// Selection messages are provided in packages that provide support for a
+// specific linguistic feature. The following snippet uses plural.Select:
+//
+// catalog.Set(language.English, "You are %d minute(s) late.",
+// plural.Select(1,
+// "one", "You are 1 minute late.",
+// "other", "You are %d minutes late."))
+//
+// In this example, a message is stored in the Catalog where one of two messages
+// is selected based on the first argument, a number. The first message is
+// selected if the argument is singular (identified by the selector "one") and
+// the second message is selected in all other cases. The selectors are defined
+// by the plural rules defined in CLDR. The selector "other" is special and will
+// always match. Each language always defines one of the linguistic categories
+// to be "other." For English, singular is "one" and plural is "other".
+//
+// Selects can be nested. This allows selecting sentences based on features of
+// multiple arguments or multiple linguistic properties of a single argument.
+//
+//
+// String interpolation
+//
+// There is often a lot of commonality between the possible variants of a
+// message. For instance, in the example above the word "minute" varies based on
+// the plural catogory of the argument, but the rest of the sentence is
+// identical. Using interpolation the above message can be rewritten as:
+//
+// catalog.Set(language.English, "You are %d minute(s) late.",
+// catalog.Var("minutes",
+// plural.Select(1, "one", "minute", "other", "minutes")),
+// catalog.String("You are %[1]d ${minutes} late."))
+//
+// Var is defined to return the variable name if the message does not yield a
+// match. This allows us to further simplify this snippet to
+//
+// catalog.Set(language.English, "You are %d minute(s) late.",
+// catalog.Var("minutes", plural.Select(1, "one", "minute")),
+// catalog.String("You are %d ${minutes} late."))
+//
+// Overall this is still only a minor improvement, but things can get a lot more
+// unwieldy if more than one linguistic feature is used to determine a message
+// variant. Consider the following example:
+//
+// // argument 1: list of hosts, argument 2: list of guests
+// catalog.Set(language.English, "%[1]v invite(s) %[2]v to their party.",
+// catalog.Var("their",
+// plural.Select(1,
+// "one", gender.Select(1, "female", "her", "other", "his"))),
+// catalog.Var("invites", plural.Select(1, "one", "invite"))
+// catalog.String("%[1]v ${invites} %[2]v to ${their} party.")),
+//
+// Without variable substitution, this would have to be written as
+//
+// // argument 1: list of hosts, argument 2: list of guests
+// catalog.Set(language.English, "%[1]v invite(s) %[2]v to their party.",
+// plural.Select(1,
+// "one", gender.Select(1,
+// "female", "%[1]v invites %[2]v to her party."
+// "other", "%[1]v invites %[2]v to his party."),
+// "other", "%[1]v invites %[2]v to their party.")
+//
+// Not necessarily shorter, but using variables there is less duplication and
+// the messages are more maintenance friendly. Moreover, languages may have up
+// to six plural forms. This makes the use of variables more welcome.
+//
+// Different messages using the same inflections can reuse variables by moving
+// them to macros. Using macros we can rewrite the message as:
+//
+// // argument 1: list of hosts, argument 2: list of guests
+// catalog.SetString(language.English, "%[1]v invite(s) %[2]v to their party.",
+// "%[1]v ${invites(1)} %[2]v to ${their(1)} party.")
+//
+// Where the following macros were defined separately.
+//
+// catalog.SetMacro(language.English, "invites", plural.Select(1, "one", "invite"))
+// catalog.SetMacro(language.English, "their", plural.Select(1,
+// "one", gender.Select(1, "female", "her", "other", "his"))),
+//
+// Placeholders use parentheses and the arguments to invoke a macro.
+//
+//
+// Looking up messages
+//
+// Message lookup using Catalogs is typically only done by specialized packages
+// and is not something the user should be concerned with. For instance, to
+// express the tardiness of a user using the related message we defined earlier,
+// the user may use the package message like so:
+//
+// p := message.NewPrinter(language.English)
+// p.Printf("You are %d minute(s) late.", 5)
+//
+// Which would print:
+// You are 5 minutes late.
+//
+//
+// This package is UNDER CONSTRUCTION and its API may change.
+package catalog // import "golang.org/x/text/message/catalog"
+
+// TODO:
+// Some way to freeze a catalog.
+// - Locking on each lockup turns out to be about 50% of the total running time
+// for some of the benchmarks in the message package.
+// Consider these:
+// - Sequence type to support sequences in user-defined messages.
+// - Garbage collection: Remove dictionaries that can no longer be reached
+// as other dictionaries have been added that cover all possible keys.
+
+import (
+ "errors"
+ "fmt"
+
+ "golang.org/x/text/internal"
+
+ "golang.org/x/text/internal/catmsg"
+ "golang.org/x/text/language"
+)
+
+// A Catalog allows lookup of translated messages.
+type Catalog interface {
+ // Languages returns all languages for which the Catalog contains variants.
+ Languages() []language.Tag
+
+ // Matcher returns a Matcher for languages from this Catalog.
+ Matcher() language.Matcher
+
+ // A Context is used for evaluating Messages.
+ Context(tag language.Tag, r catmsg.Renderer) *Context
+
+ // This method also makes Catalog a private interface.
+ lookup(tag language.Tag, key string) (data string, ok bool)
+}
+
+// NewFromMap creates a Catalog from the given map. If a Dictionary is
+// underspecified the entry is retrieved from a parent language.
+func NewFromMap(dictionaries map[string]Dictionary, opts ...Option) (Catalog, error) {
+ options := options{}
+ for _, o := range opts {
+ o(&options)
+ }
+ c := &catalog{
+ dicts: map[language.Tag]Dictionary{},
+ }
+ _, hasFallback := dictionaries[options.fallback.String()]
+ if hasFallback {
+ // TODO: Should it be okay to not have a fallback language?
+ // Catalog generators could enforce there is always a fallback.
+ c.langs = append(c.langs, options.fallback)
+ }
+ for lang, dict := range dictionaries {
+ tag, err := language.Parse(lang)
+ if err != nil {
+ return nil, fmt.Errorf("catalog: invalid language tag %q", lang)
+ }
+ if _, ok := c.dicts[tag]; ok {
+ return nil, fmt.Errorf("catalog: duplicate entry for tag %q after normalization", tag)
+ }
+ c.dicts[tag] = dict
+ if !hasFallback || tag != options.fallback {
+ c.langs = append(c.langs, tag)
+ }
+ }
+ if hasFallback {
+ internal.SortTags(c.langs[1:])
+ } else {
+ internal.SortTags(c.langs)
+ }
+ c.matcher = language.NewMatcher(c.langs)
+ return c, nil
+}
+
+// A Dictionary is a source of translations for a single language.
+type Dictionary interface {
+ // Lookup returns a message compiled with catmsg.Compile for the given key.
+ // It returns false for ok if such a message could not be found.
+ Lookup(key string) (data string, ok bool)
+}
+
+type catalog struct {
+ langs []language.Tag
+ dicts map[language.Tag]Dictionary
+ macros store
+ matcher language.Matcher
+}
+
+func (c *catalog) Languages() []language.Tag { return c.langs }
+func (c *catalog) Matcher() language.Matcher { return c.matcher }
+
+func (c *catalog) lookup(tag language.Tag, key string) (data string, ok bool) {
+ for ; ; tag = tag.Parent() {
+ if dict, ok := c.dicts[tag]; ok {
+ if data, ok := dict.Lookup(key); ok {
+ return data, true
+ }
+ }
+ if tag == language.Und {
+ break
+ }
+ }
+ return "", false
+}
+
+// Context returns a Context for formatting messages.
+// Only one Message may be formatted per context at any given time.
+func (c *catalog) Context(tag language.Tag, r catmsg.Renderer) *Context {
+ return &Context{
+ cat: c,
+ tag: tag,
+ dec: catmsg.NewDecoder(tag, r, &dict{&c.macros, tag}),
+ }
+}
+
+// A Builder allows building a Catalog programmatically.
+type Builder struct {
+ options
+ matcher language.Matcher
+
+ index store
+ macros store
+}
+
+type options struct {
+ fallback language.Tag
+}
+
+// An Option configures Catalog behavior.
+type Option func(*options)
+
+// Fallback specifies the default fallback language. The default is Und.
+func Fallback(tag language.Tag) Option {
+ return func(o *options) { o.fallback = tag }
+}
+
+// TODO:
+// // Catalogs specifies one or more sources for a Catalog.
+// // Lookups are in order.
+// // This can be changed inserting a Catalog used for setting, which implements
+// // Loader, used for setting in the chain.
+// func Catalogs(d ...Loader) Option {
+// return nil
+// }
+//
+// func Delims(start, end string) Option {}
+//
+// func Dict(tag language.Tag, d ...Dictionary) Option
+
+// NewBuilder returns an empty mutable Catalog.
+func NewBuilder(opts ...Option) *Builder {
+ c := &Builder{}
+ for _, o := range opts {
+ o(&c.options)
+ }
+ return c
+}
+
+// SetString is shorthand for Set(tag, key, String(msg)).
+func (c *Builder) SetString(tag language.Tag, key string, msg string) error {
+ return c.set(tag, key, &c.index, String(msg))
+}
+
+// Set sets the translation for the given language and key.
+//
+// When evaluation this message, the first Message in the sequence to msgs to
+// evaluate to a string will be the message returned.
+func (c *Builder) Set(tag language.Tag, key string, msg ...Message) error {
+ return c.set(tag, key, &c.index, msg...)
+}
+
+// SetMacro defines a Message that may be substituted in another message.
+// The arguments to a macro Message are passed as arguments in the
+// placeholder the form "${foo(arg1, arg2)}".
+func (c *Builder) SetMacro(tag language.Tag, name string, msg ...Message) error {
+ return c.set(tag, name, &c.macros, msg...)
+}
+
+// ErrNotFound indicates there was no message for the given key.
+var ErrNotFound = errors.New("catalog: message not found")
+
+// String specifies a plain message string. It can be used as fallback if no
+// other strings match or as a simple standalone message.
+//
+// It is an error to pass more than one String in a message sequence.
+func String(name string) Message {
+ return catmsg.String(name)
+}
+
+// Var sets a variable that may be substituted in formatting patterns using
+// named substitution of the form "${name}". The name argument is used as a
+// fallback if the statements do not produce a match. The statement sequence may
+// not contain any Var calls.
+//
+// The name passed to a Var must be unique within message sequence.
+func Var(name string, msg ...Message) Message {
+ return &catmsg.Var{Name: name, Message: firstInSequence(msg)}
+}
+
+// Context returns a Context for formatting messages.
+// Only one Message may be formatted per context at any given time.
+func (b *Builder) Context(tag language.Tag, r catmsg.Renderer) *Context {
+ return &Context{
+ cat: b,
+ tag: tag,
+ dec: catmsg.NewDecoder(tag, r, &dict{&b.macros, tag}),
+ }
+}
+
+// A Context is used for evaluating Messages.
+// Only one Message may be formatted per context at any given time.
+type Context struct {
+ cat Catalog
+ tag language.Tag // TODO: use compact index.
+ dec *catmsg.Decoder
+}
+
+// Execute looks up and executes the message with the given key.
+// It returns ErrNotFound if no message could be found in the index.
+func (c *Context) Execute(key string) error {
+ data, ok := c.cat.lookup(c.tag, key)
+ if !ok {
+ return ErrNotFound
+ }
+ return c.dec.Execute(data)
+}