1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779
#![cfg_attr(not(feature = "std"), no_std)]
//! # A minimal text template engine
//!
//! ## Overview
//! Create templates with named placeholders within it.
//!
//! Placeholders are defined by default following the handlebars syntax,
//! but can be overriden with specific boundaries.
//!
//! This library supports passing a `HashMap` or `Struct` as a context
//! in order to replace the specified placeholders.
//!
//! ## Example
//!
//! use text_placeholder::Template;
//! #[cfg(feature = "std")]
//! use std::collections::HashMap;
//!
//! #[cfg(not(feature = "std"))]
//! use hashbrown::HashMap;
//!
//! let default_template = Template::new("Hello {{first}} {{second}}!");
//!
//! let mut table = HashMap::new();
//! table.insert("first", "text");
//! table.insert("second", "placeholder");
//!
//! assert_eq!(default_template.fill_with_hashmap(&table), "Hello text placeholder!");
//!
//! // We can also specify our own boundaries:
//!
//! let custom_template = Template::new_with_placeholder("Hello $[first]] $[second]!", "$[", "]");
//!
//! assert_eq!(default_template.fill_with_hashmap(&table), "Hello text placeholder!");
use alloc::borrow::Cow;
mod token_iterator;
use token_iterator::{Token, TokenIterator};
mod error;
pub use error::{Error, Result};
#[cfg(feature = "struct_context")]
extern crate serde_json;
#[cfg(feature = "struct_context")]
use serde::Serialize;
#[cfg(feature = "std")]
use std::collections::HashMap;
#[cfg(not(feature = "std"))]
use hashbrown::HashMap;
#[macro_use]
extern crate alloc;
use alloc::{string::String, vec::Vec};
const DEFAULT_START_PLACEHOLDER: &str = "{{";
const DEFAULT_END_PLACEHOLDER: &str = "}}";
/// A template is composed of tokens, which in turn can represent plain text
/// or a named placeholder.
pub struct Template<'t> {
tokens: Vec<Token<'t>>,
}
impl<'t> Template<'t> {
/// Generates a Template with boundaries specified by the handlebars syntax,
/// this means that within the string `"hello {{key}}"` we will have `key`
/// as a named placeholder.
///
/// Example:
/// ```rust
/// # use text_placeholder::Template;
/// let template = Template::new("Hello {{key}}!");
/// ```
pub fn new(text: &'t str) -> Self {
Self {
tokens: TokenIterator::new(text, DEFAULT_START_PLACEHOLDER, DEFAULT_END_PLACEHOLDER)
.collect(),
}
}
/// Generates a Template with boundaries specified by the `start` and `end`
/// arguments.
///
/// Example:
/// ```rust
/// # use text_placeholder::Template;
/// let template = Template::new_with_placeholder("Hello [key]!", "[", "]");
/// ```
pub fn new_with_placeholder(text: &'t str, start: &'t str, end: &'t str) -> Self {
Self {
tokens: TokenIterator::new(text, start, end).collect(),
}
}
/// Fill the template's placeholders using the provided `replacements` HashMap
/// in order to to derive values for the named placeholders.
///
/// Placeholders without an associated value will be replaced with an empty string.
///
/// For a version that generates an error in case a placeholder is missing see
/// [`Template::fill_with_hashmap_strict`].
pub fn fill_with_hashmap(&self, replacements: &HashMap<&str, &str>) -> String {
self.fill_with_function(|s| Some(Cow::Borrowed(replacements.get(s).unwrap_or(&""))))
.unwrap()
}
/// Fill the template's placeholders using the provided `replacements HashMap`
/// in order to to infer values for the named placeholders.
///
/// Placeholders without an associated value will result in a `Error::PlaceholderError`.
///
/// For a version that does not generate an error in case a placeholder is missing see
/// [`Template::fill_with_hashmap`].
pub fn fill_with_hashmap_strict(&self, replacements: &HashMap<&str, &str>) -> Result<String> {
self.fill_with_function(|s| replacements.get(s).map(|s| Cow::from(*s)))
}
/// Fill the template's placeholders using the provided `replacements`
/// function in order to to derive values for the named placeholders.
///
/// `replacements` is a [`FnMut`] which may modify its environment. The
/// `key` parameter is borrowed from `Template`, and so can be stored in the
/// enclosing scope.
///
/// Returned [`Cow<str>`] may also be borrwed from the `key`, the
/// environment, or be an owned [`String`] that's computed from the key or
/// derived in some other way.
///
/// Placeholders without an associated value (the function returns `None`)
/// will result in a `Error::PlaceholderError`.
///
/// This is the most general form of replacement; the other `fill_with_`
/// methods are implemented in terms of this method.
///
/// Example:
/// ```rust
/// # use text_placeholder::Template;
/// # use std::borrow::Cow;
/// let template = Template::new("Hello {{first}} {{second}}!");
///
/// let mut idx = 0;
/// assert_eq!(
/// &*template.fill_with_function(
/// |key| {
/// idx += 1;
/// Some(Cow::Owned(format!("{key}-{idx}")))
/// })
/// .unwrap(),
/// "Hello first-1 second-2!"
/// );
/// assert_eq!(idx, 2);
/// ```
pub fn fill_with_function<'a, F>(&self, mut replacements: F) -> Result<String>
where
F: FnMut(&'t str) -> Option<Cow<'a, str>> + 'a,
{
let mut result = String::new();
for segment in &self.tokens {
match segment {
Token::Text(s) => result.push_str(s),
Token::Placeholder(s) => match replacements(s) {
Some(value) => result.push_str(&value),
None => {
let message = format!("missing value for placeholder named '{s}'.");
return Err(Error::PlaceholderError(message));
}
},
}
}
Ok(result)
}
#[cfg(feature = "struct_context")]
/// Fill the template's placeholders using the provided `replacements struct`
/// in order to to derive values for the named placeholders. The provided struct
/// must implement `serde::Serialize`.
///
/// Placeholders without an associated value or with values that cannot be converted
/// to an str will be replaced with an empty string.
///
/// For a version that generates an error in case a placeholder is missing see
/// [`Template::fill_with_struct_strict`].
pub fn fill_with_struct<R>(&self, replacements: &R) -> Result<String>
where
R: Serialize,
{
let replacements = serde_json::to_value(replacements)?;
let result = self
.fill_with_function(|s| {
Some(Cow::Borrowed(
replacements.get(s).and_then(|v| v.as_str()).unwrap_or(""),
))
})
.unwrap();
Ok(result)
}
#[cfg(feature = "struct_context")]
/// Fill the template's placeholders using the provided `replacements struct`
/// in order to to infer values for the named placeholders. The provided struct
/// must implement `serde::Serialize`.
///
/// Placeholders without an associated value or with values that cannot be converted
/// to an str will result in a `Error::PlaceholderError`.
///
/// For a version that does not generate an error in case a placeholder is missing see
/// [`Template::fill_with_struct`].
pub fn fill_with_struct_strict<R>(&self, replacements: &R) -> Result<String>
where
R: Serialize,
{
let replacements = serde_json::to_value(replacements)?;
self.fill_with_function(|s| {
replacements
.get(s)
.and_then(|v| v.as_str().map(Cow::Borrowed))
})
}
}
#[cfg(test)]
mod tests {
use alloc::{
borrow::{Cow, ToOwned},
string::ToString,
vec::Vec,
};
#[cfg(feature = "std")]
use std::collections::HashMap;
use super::Template;
#[cfg(not(feature = "std"))]
use hashbrown::HashMap;
#[cfg(feature = "struct_context")]
use serde::Serialize;
// ---------------------
// | fill_with_hashmap |
// ---------------------
#[test]
fn test_hashmap_no_replacements() {
let table = HashMap::new();
assert_eq!(
Template::new("hello world").fill_with_hashmap(&table),
"hello world"
);
}
#[test]
fn test_hashmap_replacement_start_line() {
let mut table = HashMap::new();
table.insert("placeholder", "hello");
assert_eq!(
Template::new("{{placeholder}} world").fill_with_hashmap(&table),
"hello world"
);
}
#[test]
fn test_hashmap_replacement_middle_line() {
let mut table = HashMap::new();
table.insert("placeholder", "crazy");
assert_eq!(
Template::new("hello {{placeholder}} world").fill_with_hashmap(&table),
"hello crazy world"
);
}
#[test]
fn test_hashmap_replacement_end_line() {
let mut table = HashMap::new();
table.insert("placeholder", "world");
assert_eq!(
Template::new("hello {{placeholder}}").fill_with_hashmap(&table),
"hello world"
);
}
#[test]
fn test_hashmap_multiple_replacements() {
let mut table = HashMap::new();
table.insert("first", "one");
table.insert("second", "two");
table.insert("third", "three");
assert_eq!(
Template::new("{{first}} {{second}} {{third}}").fill_with_hashmap(&table),
"one two three"
);
}
#[test]
fn test_hashmap_missing_starting_boundaries() {
let mut table = HashMap::new();
table.insert("placeholder", "world");
assert_eq!(
Template::new("hello placeholder}}").fill_with_hashmap(&table),
"hello placeholder}}"
);
}
#[test]
fn test_hashmap_missing_closing_boundaries() {
let mut table = HashMap::new();
table.insert("placeholder", "world");
assert_eq!(
Template::new("hello {{placeholder").fill_with_hashmap(&table),
"hello {{placeholder"
);
}
#[test]
fn test_hashmap_missing_replacements() {
let table = HashMap::new();
assert_eq!(
Template::new("hello {{placeholder}}").fill_with_hashmap(&table),
"hello "
);
}
// ----------------------------
// | fill_with_hashmap_strict |
// ----------------------------
#[test]
fn test_hashmap_strict_no_replacements() {
let table = HashMap::new();
assert_eq!(
Template::new("hello world")
.fill_with_hashmap_strict(&table)
.unwrap(),
"hello world"
);
}
#[test]
fn test_hashmap_strict_replacement_start_line() {
let mut table = HashMap::new();
table.insert("placeholder", "hello");
assert_eq!(
Template::new("{{placeholder}} world")
.fill_with_hashmap_strict(&table)
.unwrap(),
"hello world"
);
}
#[test]
fn test_hashmap_strict_replacement_middle_line() {
let mut table = HashMap::new();
table.insert("placeholder", "crazy");
assert_eq!(
Template::new("hello {{placeholder}} world")
.fill_with_hashmap_strict(&table)
.unwrap(),
"hello crazy world"
);
}
#[test]
fn test_hashmap_strict_replacement_end_line() {
let mut table = HashMap::new();
table.insert("placeholder", "world");
assert_eq!(
Template::new("hello {{placeholder}}")
.fill_with_hashmap_strict(&table)
.unwrap(),
"hello world"
);
}
#[test]
fn test_hashmap_strict_multiple_replacements() {
let mut table = HashMap::new();
table.insert("first", "one");
table.insert("second", "two");
table.insert("third", "three");
assert_eq!(
Template::new("{{first}} {{second}} {{third}}")
.fill_with_hashmap_strict(&table)
.unwrap(),
"one two three"
);
}
#[test]
fn test_hashmap_strict_missing_starting_boundaries() {
let mut table = HashMap::new();
table.insert("placeholder", "world");
assert_eq!(
Template::new("hello placeholder}}")
.fill_with_hashmap_strict(&table)
.unwrap(),
"hello placeholder}}"
);
}
#[test]
fn test_hashmap_strict_missing_closing_boundaries() {
let mut table = HashMap::new();
table.insert("placeholder", "world");
assert_eq!(
Template::new("hello {{placeholder")
.fill_with_hashmap_strict(&table)
.unwrap(),
"hello {{placeholder"
);
}
#[test]
fn test_hashmap_strict_missing_replacements() {
let table = HashMap::new();
assert_eq!(
Template::new("hello {{placeholder}}").fill_with_hashmap_strict(&table).map_err(|e| e.to_string()),
Err("Error while replacing placeholder. Reason: missing value for placeholder named 'placeholder'.".to_owned())
);
}
// ----------------------
// | fill_with_function |
// ----------------------
#[test]
fn test_function_replacements() {
let template = Template::new("hello {{foo}} {{bar}}");
let mut kw = Vec::new();
let mut idx = 0;
let result = template
.fill_with_function(|s| {
kw.push(s);
idx += 1;
Some(Cow::Owned(format!("{s}{idx}")))
})
.expect("fill_with_function failed");
assert_eq!(result, "hello foo1 bar2");
assert_eq!(kw, vec!["foo", "bar"]);
}
// --------------------
// | fill_with_struct |
// --------------------
#[cfg(feature = "struct_context")]
#[test]
fn test_struct_no_replacements() {
#[derive(Serialize)]
struct Context {}
let context = Context {};
assert_eq!(
Template::new("hello world")
.fill_with_struct(&context)
.unwrap(),
"hello world"
);
}
#[cfg(feature = "struct_context")]
#[test]
fn test_struct_replacement_start_line() {
#[derive(Serialize)]
struct Context {
placeholder: String,
}
let context = Context {
placeholder: "hello".to_string(),
};
assert_eq!(
Template::new("{{placeholder}} world")
.fill_with_struct(&context)
.unwrap(),
"hello world"
);
}
#[cfg(feature = "struct_context")]
#[test]
fn test_struct_replacement_middle_line() {
#[derive(Serialize)]
struct Context {
placeholder: String,
}
let context = Context {
placeholder: "crazy".to_string(),
};
assert_eq!(
Template::new("hello {{placeholder}} world")
.fill_with_struct(&context)
.unwrap(),
"hello crazy world"
);
}
#[cfg(feature = "struct_context")]
#[test]
fn test_struct_replacement_end_line() {
#[derive(Serialize)]
struct Context {
placeholder: String,
}
let context = Context {
placeholder: "world".to_string(),
};
assert_eq!(
Template::new("hello {{placeholder}}")
.fill_with_struct(&context)
.unwrap(),
"hello world"
);
}
#[cfg(feature = "struct_context")]
#[test]
fn test_struct_multiple_replacements() {
#[derive(Serialize)]
struct Context {
first: String,
second: String,
third: String,
}
let context = Context {
first: "one".to_string(),
second: "two".to_string(),
third: "three".to_string(),
};
assert_eq!(
Template::new("{{first}} {{second}} {{third}}")
.fill_with_struct(&context)
.unwrap(),
"one two three"
);
}
#[cfg(feature = "struct_context")]
#[test]
fn test_struct_missing_starting_boundaries() {
#[derive(Serialize)]
struct Context {
placeholder: String,
}
let context = Context {
placeholder: "world".to_string(),
};
assert_eq!(
Template::new("hello placeholder}}")
.fill_with_struct(&context)
.unwrap(),
"hello placeholder}}"
);
}
#[cfg(feature = "struct_context")]
#[test]
fn test_struct_missing_closing_boundaries() {
#[derive(Serialize)]
struct Context {
placeholder: String,
}
let context = Context {
placeholder: "world".to_string(),
};
assert_eq!(
Template::new("hello {{placeholder")
.fill_with_struct(&context)
.unwrap(),
"hello {{placeholder"
);
}
#[cfg(feature = "struct_context")]
#[test]
fn test_struct_missing_replacements() {
#[derive(Serialize)]
struct Context {
different: String,
}
let context = Context {
different: "world".to_string(),
};
assert_eq!(
Template::new("hello {{placeholder}}")
.fill_with_struct(&context)
.unwrap(),
"hello "
);
}
// ---------------------------
// | fill_with_struct_strict |
// ---------------------------
#[cfg(feature = "struct_context")]
#[test]
fn test_struct_strict_no_replacements() {
#[derive(Serialize)]
struct Context {}
let context = Context {};
assert_eq!(
Template::new("hello world")
.fill_with_struct_strict(&context)
.unwrap(),
"hello world"
);
}
#[cfg(feature = "struct_context")]
#[test]
fn test_struct_strict_replacement_start_line() {
#[derive(Serialize)]
struct Context {
placeholder: String,
}
let context = Context {
placeholder: "hello".to_string(),
};
assert_eq!(
Template::new("{{placeholder}} world")
.fill_with_struct_strict(&context)
.unwrap(),
"hello world"
);
}
#[cfg(feature = "struct_context")]
#[test]
fn test_struct_strict_replacement_middle_line() {
#[derive(Serialize)]
struct Context {
placeholder: String,
}
let context = Context {
placeholder: "crazy".to_string(),
};
assert_eq!(
Template::new("hello {{placeholder}} world")
.fill_with_struct_strict(&context)
.unwrap(),
"hello crazy world"
);
}
#[cfg(feature = "struct_context")]
#[test]
fn test_struct_strict_replacement_end_line() {
#[derive(Serialize)]
struct Context {
placeholder: String,
}
let context = Context {
placeholder: "world".to_string(),
};
assert_eq!(
Template::new("hello {{placeholder}}")
.fill_with_struct_strict(&context)
.unwrap(),
"hello world"
);
}
#[cfg(feature = "struct_context")]
#[test]
fn test_struct_strict_multiple_replacements() {
#[derive(Serialize)]
struct Context {
first: String,
second: String,
third: String,
}
let context = Context {
first: "one".to_string(),
second: "two".to_string(),
third: "three".to_string(),
};
assert_eq!(
Template::new("{{first}} {{second}} {{third}}")
.fill_with_struct_strict(&context)
.unwrap(),
"one two three"
);
}
#[cfg(feature = "struct_context")]
#[test]
fn test_struct_strict_missing_starting_boundaries() {
#[derive(Serialize)]
struct Context {
placeholder: String,
}
let context = Context {
placeholder: "world".to_string(),
};
assert_eq!(
Template::new("hello placeholder}}")
.fill_with_struct_strict(&context)
.unwrap(),
"hello placeholder}}"
);
}
#[cfg(feature = "struct_context")]
#[test]
fn test_struct_strict_missing_closing_boundaries() {
#[derive(Serialize)]
struct Context {
placeholder: String,
}
let context = Context {
placeholder: "world".to_string(),
};
assert_eq!(
Template::new("hello {{placeholder")
.fill_with_struct_strict(&context)
.unwrap(),
"hello {{placeholder"
);
}
#[cfg(feature = "struct_context")]
#[test]
fn test_struct_strict_missing_replacements() {
#[derive(Serialize)]
struct Context {
different: String,
}
let context = Context {
different: "world".to_string(),
};
assert_eq!(
Template::new("hello {{placeholder}}").fill_with_struct_strict(&context).map_err(|e| e.to_string()),
Err("Error while replacing placeholder. Reason: missing value for placeholder named 'placeholder'.".to_owned())
);
}
}