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kumo.string.eval_template(NAME, SOURCE, CONTEXT)

Since: Version 2025.03.19-1d3f1f67

The functionality described in this section requires version 2025.03.19-1d3f1f67 of KumoMTA, or a more recent version.

Evaluates a minijinja template.

The parameters are:

  • NAME - the nominal "file name" for the template. No actual file I/O is performed; this parameter tells the template engine what the filename would have been if it were loaded from disk. The filename is used to decide what strategy should be used for automatic output escaping. For example, if the name ends with .json or .html then appropriate json or html entity escaping will automatically be applied to the output.
  • SOURCE - the template source code. This must follow the template syntax.
  • CONTEXT - an object that defines the variables that are available to the template engine.
-- This will print `"John"`
print(
  kumo.string.eval_template('example.json', [[{{ name }}]], { name = 'John' })
)

local kumo = require 'kumo'

local log_record = kumo.serde.json_parse [=[
{
    "type": "Delivery",
    "id": "1d98076abbbc11ed940250ebf67f93bd",
    "sender": "user@sender.example.com",
    "recipient": "user@recipient.example.com",
    "queue": "campaign:tenant@domain",
    "site": "source2->(alt1|alt2|alt3|alt4)?.gmail-smtp-in.l.google.com.",
    "size": 1047,
    "response": {
        "code": 250,
        "enhanced_code": {
            "class": 2,
            "subject": 0,
            "detail": 0
        },
        "content": "OK ids=8a5475ccbbc611eda12250ebf67f93bd",
        "command": "."
    },
    "peer_address": {
        "name": "gmail-smtp-in.l.google.com.",
        "addr": "142.251.2.27"
    },
    "timestamp": 1678069691,
    "created": 1678069691,
    "num_attempts": 0,
    "bounce_classification": "Uncategorized",
    "egress_pool": "pool0",
    "egress_source": "source2",
    "source_address": {
        "address": "10.0.0.1:53210",
        "protocol": "socks5",
        "server": "192.168.1.1:5000"
    },
    "feedback_report": null,
    "meta": {},
    "headers": {},
    "delivery_protocol": "ESMTP",
    "reception_protocol": "ESMTP",
    "bogus": null,
    "nodeid": "557f3ad4-2c8c-11ee-976e-782d7e12e173",
    "tls_cipher": "TLS_AES_256_GCM_SHA384",
    "tls_protocol_version": "TLSv1.3",
    "tls_peer_subject_name": ["C=US","ST=CA","L=SanFrancisco","O=Fort-Funston",
                              "OU=MyOrganizationalUnit","CN=do.havedane.net",
                              "name=EasyRSA","emailAddress=me@myhost.mydomain"],
    "session_id": "9bcd689e-23d9-41b7-a015-63a1382f8b57"
}
]=]

print(kumo.string.eval_template(
  'log.json',
  [[{}
]],
  { log_record = log_record }
))