Enhancement: Create a new `{{locale}}` placeholder for i18n content

[estruyf]

Create a new {{locale}} placeholder for i18n content and their preview paths.

And it might serve as a good groundwork for i18n improvements. Something like this would be beneficial: "previewPath": "{{localePath}}/{{pathToken.relPath}}".

{{locale}} should become its own placeholder which can be used in the preview path as well. Good feedback. I'll create a new issue for it to track it.

Originally posted by @estruyf in #806 (comment)

[estruyf]

New {{locale}} placeholder can be used in the previewPath. For example: "previewPath": "{{locale}}/blog".

You can also ignore locales, for instance, if you do not want to include the en locale in the preview path, but all others are fine. Examples:

• {{locale|ignore:en}}: ignore only en
• {{locale|ignore:en,nl}}: ignore en and nl

@theinfinit feel free to give it a try.

To document

• Add the locale placeholder
• Add the documentation to ignore certain locales

[theinfinit]

Tested with beta v10.2.9236459.

For now, I can't get it to work 🫣

1. Simple case

// 👁️ — pages visible in the dashboard

$ tree content
src/
└── content/
    └── astro-content-collection/
        └── reference/
            └── 👁️ index.md
            └── 👁️ example.md
        └── de/
            └── reference/
                └── index.md // http://localhost:4321/de/reference/ ✅
                └── example.md // http://localhost:4321/de/example/ -> Expected http://localhost:4321/de/reference/example/
            👁️ index.mdx // http://localhost:4321/de/ ✅
        👁️ index.mdx

"frontMatter.content.i18n": [
    { "title": "English", "locale": "en", "path": "." },
    { "title": "Deutsch", "locale": "de", "path": "de" }
  ],
"frontMatter.content.pageFolders": [
  {
    "title": "Docs",
    "path": "[[workspace]]/src/content/docs/",
    "excludeSubdir": true,
    "previewPath": "{{locale}}",
    "defaultLocale": "en"
  },
  {
    "title": "Guides",
    "path": "[[workspace]]/src/content/docs/guides",
    "previewPath": "{{locale}}/guides",
    "defaultLocale": "en"
  },
  {
    "title": "Reference",
    "path": "[[workspace]]/src/content/docs/reference",
    "previewPath": "{{locale}}/reference",
    "defaultLocale": "en"
  }
],

---

2. Partially modified, complex configuration:

Under Showing: Docs filter in the dashboard, only English pages are visible. Pages from other languages aren't included in the dashboard at all.

"frontMatter.content.i18n": [
  { "title": "English", "locale": "en", "path": "." },
  { "title": "Deutsch", "locale": "de", "path": "de" },
  { "title": "Español", "locale": "es", "path": "es" }
],
"frontMatter.content.pageFolders": [
  {
    "title": "Root",
    "path": "[[workspace]]/src/content/astro-content-collection/",
    "previewPath": "{{pathToken.relPath}}/",
    "excludeSubdir": true,
    "defaultLocale": "en",
  },
  {
    "title": "Docs",
    "path": "[[workspace]]/src/content/astro-content-collection/docs/",
    "previewPath": "{{locale}}/docs/{{pathToken.relPath}}/", // 👈 added `{{locale}}`
    "excludeSubdir": true,
    "defaultLocale": "en",
    // Removed "locales": [...]
  },
  {
    "title": "Docs / Guides",
    "path": "[[workspace]]/src/content/astro-content-collection/docs/guides",
    "previewPath": "/docs/guides/",
    "defaultLocale": "en",
    "locales": [
      { "title": "English", "locale": "en" },
      { "title": "Deutsch", "locale": "de",    "path": "../../../de/docs/guides/" },
      { "title": "Español", "locale": "es",    "path": "../../../es/docs/guides/" },
    ],
  },
]

Preview path for localized page de/docs/manual-setup.md:

<!-- Received -->
http://localhost:4321/docs/manual-setup/

<!-- Expected -->
http://localhost:4321/de/docs/manual-setup/

---

Previous, working configuration:

"frontMatter.content.pageFolders": [
  {
    "title": "Root",
    "path": "[[workspace]]/src/content/astro-content-collection/",
    "previewPath": "{{pathToken.relPath}}/",
    "excludeSubdir": true,
    "defaultLocale": "en",
  },
  {
    "title": "Docs",
    "path": "[[workspace]]/src/content/astro-content-collection/docs/",
    "previewPath": "/docs/{{pathToken.relPath}}/",
    "excludeSubdir": true,
    "defaultLocale": "en",
    "locales": [
      { "title": "English",              "locale": "en" },
      { "title": "Deutsch",              "locale": "de",    "path": "../../de/docs/" },
      { "title": "Español",              "locale": "es",    "path": "../../es/docs/" }
    ],
  },
  {
    "title": "Docs / Guides",
    "path": "[[workspace]]/src/content/astro-content-collection/docs/guides",
    "previewPath": "/docs/guides/",
    "defaultLocale": "en",
    "locales": [
      { "title": "English",              "locale": "en" },
      { "title": "Deutsch",              "locale": "de",    "path": "../../../de/docs/guides/" },
      { "title": "Español",              "locale": "es",    "path": "../../../es/docs/guides/" },
    ],
  },
]

---

3. {{locale}} added to every pageFolders entry

Localized pages are not visible in the dashboard too. The only visible, localized page was from "Root" pageFolder.

Because of that, I tested preview for that page (de/index.md), and got http://localhost:4321/316/de/ (notice strange 316 subpath, which is not present anywhere).

"frontMatter.content.i18n": [
  { "title": "English", "locale": "en", "path": "." },
  { "title": "Deutsch", "locale": "de", "path": "de" },
  { "title": "Español", "locale": "es", "path": "es" }
],
"frontMatter.content.pageFolders": [
  {
    "title": "Root",
    "path": "[[workspace]]/src/content/astro-content-collection/",
    "previewPath": "{{locale}}/{{pathToken.relPath}}/",
    "excludeSubdir": true,
    "defaultLocale": "en",
  },
  {
    "title": "Docs",
    "path": "[[workspace]]/src/content/astro-content-collection/docs/",
    "previewPath": "{{locale}}/docs/{{pathToken.relPath}}/", 
    /* Also tested with: 
     * "previewPath": "{{locale}}/docs", 
     * but got the same "316" preview path: `http://localhost:4321/316/de/`
     */
    "excludeSubdir": true,
    "defaultLocale": "en",
  },
  {
    "title": "Docs / Guides",
    "path": "[[workspace]]/src/content/astro-content-collection/docs/guides",
    "previewPath": "{{locale}}/docs/guides/",
    "defaultLocale": "en",
  },
]

[estruyf]

1. Simple case

There is a config issue with the folder paths. Your DE content should be located in src/content/astro-content-collection/reference/de/, not in src/content/astro-content-collection/reference/de/reference.

The results should all be as expected when configured like the first path.

2. Partially modified, complex configuration

Same issue as the first one. Your i18n content should be in src/content/astro-content-collection/docs/de/manual-setup.md, instead of src/content/astro-content-collection/docs/de/docs/manual-setup.md

3. {{locale}} added to every pageFolders entry

Fix coming up, this has to do with the date formatting on the pathname, but replaced the logic.