`template://`¶

Producer-only Go template renderer. Uses stdlib html/template (auto-escaping) or text/template (no escaping), augmented with the Masterminds/sprig/v3 helper set (~100 helpers across strings, math, dates, dicts, lists, regex, semver, crypto). The exchange body is the data context (map[string]any or JSON-decoded equivalent).

Use template:// to compose HTML reports, email bodies, prompts, configuration files — anything where a parameterized text artifact comes out of structured input.

Producer-only — CreateConsumer returns ErrConsumerNotSupported.

URI shape¶

template://<name>?path=templates/report.html&engine=html&sprig=true&missingKey=zero

Parameters¶

Param	Type	Default	Description
`path`	string	—	Single template file. Mutually exclusive with `glob` / `inline`.
`glob`	string	—	Glob pattern. First match is the entry template; the rest are available as named blocks (`{{ template "name" . }}`).
`inline`	string	—	Inline template source (URL-encoded).
`engine`	enum	`html`	`html` (auto-escapes per context) or `text` (raw).
`sprig`	boolean	`true`	Install the sprig/v3 helper FuncMap.
`missingKey`	enum	`zero`	Behavior on missing key: `default`/`invalid` → `<no value>`, `zero` → zero value, `error` → abort.
`name`	string	derived	Override the named entry template to execute.
`contentType`	string	`text/html`	Content-Type set on the output.
`trimSpace`	boolean	`false`	Trim leading/trailing whitespace from output.
`leftDelim`	string	`{{`	Override left action delimiter.
`rightDelim`	string	`}}`	Override right action delimiter.

Source resolution¶

URI param path=...
URI param glob=...
URI param inline=...
Exchange header template.source (template string)
Exchange header template.path (file path)

Compiled templates are cached per (kind, source) tuple on the endpoint, so file reads only happen on first use (and a cache miss on a different source kind).

Headers¶

Header	Direction	Description
`template.source`	Read	Inline template per exchange.
`template.path`	Read	Template file path per exchange.
`template.engine`	Written	`html` or `text`.
`template.bytes`	Written	Output length.
`Content-Type`	Written	From the `contentType` param.

The output body is a string. The component overwrites both Out() and In() so the next pipeline step sees the rendered text rather than the data context.

Body coercion¶

The body is "dot-into-able" Go data. JSON-encoded strings / byte slices are auto-parsed (so a Starlang output application/json step upstream "just works"). Maps and slices pass through. Other types pass through and dot-expressions get evaluated against them.

Examples¶

Inline HTML template, sprig-enabled:

- set-body:
    starlang: '{ "user": payload.name, "tags": ["a","b","c"] }'
- target: |
    template://greet?engine=html&inline=
    %3Ch1%3EHello%20%7B%7B%20.user%20%7C%20title%20%7D%7D%21%3C%2Fh1%3E
    %3Cul%3E%7B%7B%20range%20.tags%20%7D%7D%3Cli%3E%7B%7B%20.%20%7D%7D%3C%2Fli%3E%7B%7B%20end%20%7D%7D%3C%2Ful%3E

File-backed template with named subtemplates:

templates/report.html
templates/_header.html
templates/_footer.html

- target: template://report?glob=templates/*.html&name=report.html

Pick a template at runtime:

- set-header:
    name: template.path
    starlang: '"templates/" ++ payload.type ++ ".html"'
- target: template://dispatch?engine=html

Text template (no escaping) — handy for prompt construction:

- target: template://prompt?engine=text&contentType=text/plain&path=prompts/research.txt&missingKey=error

Behavior notes¶

Caching — first call per (kind, source) parses; subsequent calls reuse. Changing the file on disk requires restarting the endpoint (no auto-reload).
missingKey defaults to zero — strictest sensible value for downstream parsers (no stray <no value> text). Set missingKey=error to fail-fast when a key is missing.
SetRootDir(...) — when called programmatically, restricts path= / glob= lookups to a directory; paths escaping the root via .. are rejected. The default component (no root) accepts any readable file path the process can open.
sprig — by default installed; disable with sprig=false for strict, no-extras rendering.
HTML auto-escape — context-aware per html/template's rules ({{ . }} inside <a href=""> URL-escapes, inside an HTML element body it HTML-escapes, etc.). Use engine=text to bypass this when generating non-HTML output (CSV, plain text, prompts, code).

Source¶

pkg/component/template/template.go

template://¶