hcl/expr/
template_expr.rs

1use crate::{Error, Identifier, Result};
2use serde::Deserialize;
3use std::fmt;
4use std::str::FromStr;
5
6/// A template expression embeds a program written in the template sub-language as an expression.
7///
8/// This type wraps the raw template string representation. Refer to the documentation of the
9/// [`template`][`crate::template`] module if you need to parse and further evaluate the raw
10/// template.
11#[derive(Deserialize, Debug, Clone, PartialEq, Eq)]
12pub enum TemplateExpr {
13    /// A quoted template expression is delimited by quote characters (`"`) and defines a template
14    /// as a single-line expression with escape characters. The raw template string may contain
15    /// escape sequences.
16    QuotedString(String),
17    /// A heredoc template expression is introduced by a `<<` sequence and defines a template via a
18    /// multi-line sequence terminated by a user-chosen delimiter. The raw template string in the
19    /// heredoc may contain escape sequences.
20    Heredoc(Heredoc),
21}
22
23impl TemplateExpr {
24    /// Returns the template as a `&str`.
25    pub(crate) fn as_str(&self) -> &str {
26        match self {
27            TemplateExpr::QuotedString(s) => s,
28            TemplateExpr::Heredoc(heredoc) => &heredoc.template,
29        }
30    }
31}
32
33impl From<&str> for TemplateExpr {
34    fn from(s: &str) -> Self {
35        TemplateExpr::QuotedString(s.to_owned())
36    }
37}
38
39impl From<String> for TemplateExpr {
40    fn from(string: String) -> Self {
41        TemplateExpr::QuotedString(string)
42    }
43}
44
45impl From<Heredoc> for TemplateExpr {
46    fn from(heredoc: Heredoc) -> Self {
47        TemplateExpr::Heredoc(heredoc)
48    }
49}
50
51impl fmt::Display for TemplateExpr {
52    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
53        f.write_str(self.as_str())
54    }
55}
56
57/// A heredoc template expression is introduced by a `<<` sequence and defines a template via a
58/// multi-line sequence terminated by a user-chosen delimiter.
59#[derive(Deserialize, Debug, Clone, PartialEq, Eq)]
60pub struct Heredoc {
61    /// The delimiter identifier that denotes the heredoc start and end.
62    pub delimiter: Identifier,
63    /// The raw template contained in the heredoc.
64    pub template: String,
65    /// The heredoc strip mode.
66    pub strip: HeredocStripMode,
67}
68
69impl Heredoc {
70    /// Creates a new `Heredoc` with the provided delimiter and template body.
71    pub fn new<T>(delimiter: Identifier, template: T) -> Heredoc
72    where
73        T: Into<String>,
74    {
75        Heredoc {
76            delimiter,
77            template: template.into(),
78            strip: HeredocStripMode::default(),
79        }
80    }
81
82    /// Sets the heredoc strip mode to use on the template.
83    pub fn with_strip_mode(mut self, strip: HeredocStripMode) -> Heredoc {
84        self.strip = strip;
85        self
86    }
87}
88
89/// The strip behaviour for the template contained in the heredoc.
90#[derive(Debug, Clone, Copy, PartialEq, Eq, Default)]
91pub enum HeredocStripMode {
92    /// Do not strip leading whitespace.
93    #[default]
94    None,
95    /// Any literal string at the start of each line is analyzed to find the minimum number
96    /// of leading spaces, and then that number of prefix spaces is removed from all line-leading
97    /// literal strings. The final closing marker may also have an arbitrary number of spaces
98    /// preceding it on its line.
99    Indent,
100}
101
102impl HeredocStripMode {
103    /// Returns the string representation of the heredoc strip mode. This is the part before the
104    /// delimiter identifier.
105    pub fn as_str(&self) -> &'static str {
106        match self {
107            HeredocStripMode::None => "<<",
108            HeredocStripMode::Indent => "<<-",
109        }
110    }
111}
112
113impl FromStr for HeredocStripMode {
114    type Err = Error;
115
116    fn from_str(s: &str) -> Result<Self> {
117        match s {
118            "<<" => Ok(HeredocStripMode::None),
119            "<<-" => Ok(HeredocStripMode::Indent),
120            _ => Err(Error::new(format!("invalid heredoc strip mode: `{s}`"))),
121        }
122    }
123}
hcl/expr/template_expr.rs

hcl/expr/
template_expr.rs
