`text_template`

text_template renders a Go text/template template during build evaluation and returns its output as a Starlark string.

Load it from API version 1:

load("@text@1", "text_template")

Arguments

Argument	Required	Description
`template`	Yes	Go template source string.
`data`	No	Template data. Supports `None`, booleans, strings, integers, floats, lists, tuples, and dictionaries with string keys. Defaults to `None`.
`missing_key`	No	Missing map key behavior: `"error"` fails, `"zero"` uses map element zero value, and `"keep"` uses Go template default behavior. Defaults to `"keep"`.
`trim`	No	Strip leading and trailing whitespace from final output. Defaults to `False`.
`funcs`	No	Dictionary mapping template function names to Starlark callables.
`name`	No	Template name shown in parse and execution diagnostics. Defaults to `"text_template"`.
`dedent`	No	Remove indentation shared by every nonblank template source line and the first blank line. This preserves the newline before a closing multiline-string delimiter. Defaults to `False`.

With Starlark dictionaries, "zero" and "keep" both usually print <no value> because dictionary values can have mixed types. Use "error" when every referenced key must exist.

Example

load("@text@1", "text_template")

result = text_template(
    """
    Hello {{ .user.name }},

    {{ if .user.is_admin }}
    You have administrator access.
    {{ else }}
    You have standard access.
    {{ end }}

    Projects:
    {{ range .projects }}
    - {{ .name }}{{ if .active }} (active){{ end }}
    {{ end }}
    """,
    data = {
        "user": {
            "name": "Alice",
            "is_admin": True,
        },
        "projects": [
            {"name": "Atlas", "active": True},
            {"name": "Beacon", "active": False},
        ],
    },
    dedent = True,
)

Custom Functions

Template function arguments are converted back to Starlark values. Return values are converted to template values.

def upper(value):
    return value.upper()

message = text_template(
    "Hello {{ upper .name }}",
    data = {"name": "Alice"},
    funcs = {"upper": upper},
    name = "greeting",
)