Drop the serde_json dependency

npmccallum · npmccallum · commit 430f10647049 · 2021-08-12T15:23:29.000-04:00
This implements an internal `Value` type which functions like `serde_json::Value`. Note that because this commit changes the `Error` type, this is an API-breaking change. Resolves: #1 Signed-off-by: Nathaniel McCallum <nathaniel@congru.us>
diff --git a/Cargo.toml b/Cargo.toml
@@ -16,7 +16,6 @@ maintenance = { status = "passively-maintained" }
 
 [dependencies]
 serde = "1.0"
-serde_json = "1.0"
 
 [dev-dependencies]
 serde_derive = "1.0"
diff --git a/src/error.rs b/src/error.rs
@@ -1,11 +1,15 @@
 //! Module containing the error type returned by TinyTemplate if an error occurs.
 
 use instruction::{path_to_str, PathSlice};
-use serde_json::Error as SerdeJsonError;
-use serde_json::Value;
+use value::Value;
+
 use std::error::Error as StdError;
 use std::fmt;
 
+/// An opaque type representing a serialization error.
+#[derive(Debug)]
+pub struct SerializationError(super::value::Error);
+
 /// Enum representing the potential errors that TinyTemplate can encounter.
 #[derive(Debug)]
 #[non_exhaustive]
@@ -20,9 +24,7 @@ pub enum Error {
         line: usize,
         column: usize,
     },
-    SerdeError {
-        err: SerdeJsonError,
-    },
+    SerializationError(SerializationError),
     GenericError {
         msg: String,
     },
@@ -42,9 +44,9 @@ pub enum Error {
         column: usize,
     },
 }
-impl From<SerdeJsonError> for Error {
-    fn from(err: SerdeJsonError) -> Error {
-        Error::SerdeError { err }
+impl From<super::value::Error> for Error {
+    fn from(err: super::value::Error) -> Error {
+        Error::SerializationError(SerializationError(err))
     }
 }
 impl From<fmt::Error> for Error {
@@ -67,8 +69,8 @@ impl fmt::Display for Error {
                     line, column, msg
                 )
             }
-            Error::SerdeError { err } => {
-                write!(f, "Unexpected serde error while converting the context to a serde_json::Value. Error: {}", err)
+            Error::SerializationError(err) => {
+                write!(f, "Unexpected error during serialization. Error: {}", err.0)
             }
             Error::GenericError { msg } => {
                 write!(f, "{}", msg)
@@ -108,7 +110,7 @@ impl StdError for Error {
         match self {
             Error::ParseError { .. } => "ParseError",
             Error::RenderError { .. } => "RenderError",
-            Error::SerdeError { .. } => "SerdeError",
+            Error::SerializationError { .. } => "SerializationError",
             Error::GenericError { msg } => &msg,
             Error::StdFormatError { .. } => "StdFormatError",
             Error::CalledTemplateError { .. } => "CalledTemplateError",
@@ -149,18 +151,6 @@ pub(crate) fn lookup_error(source: &str, step: &str, path: PathSlice, current: &
     }
 }
 
-pub(crate) fn truthiness_error(source: &str, path: PathSlice) -> Error {
-    let (line, column) = get_offset(source, path.last().unwrap());
-    Error::RenderError {
-        msg: format!(
-            "Path '{}' produced a value which could not be checked for truthiness.",
-            path_to_str(path)
-        ),
-        line,
-        column,
-    }
-}
-
 pub(crate) fn unprintable_error() -> Error {
     Error::GenericError {
         msg: "Expected a printable value but found array or object.".to_string(),
diff --git a/src/lib.rs b/src/lib.rs
@@ -63,7 +63,6 @@
 //!
 
 extern crate serde;
-extern crate serde_json;
 
 #[cfg(test)]
 #[cfg_attr(test, macro_use)]
@@ -74,13 +73,14 @@ pub mod error;
 mod instruction;
 pub mod syntax;
 mod template;
+mod value;
 
 use error::*;
 use serde::Serialize;
-use serde_json::Value;
 use std::collections::HashMap;
 use std::fmt::Write;
 use template::Template;
+use value::Value;
 
 /// Type alias for closures which can be used as value formatters.
 pub type ValueFormatter = dyn Fn(&Value, &mut String) -> Result<()>;
@@ -119,20 +119,25 @@ pub fn escape(value: &str, output: &mut String) {
 /// Values are formatted as follows:
 ///
 /// * `Value::Null` => the empty string
-/// * `Value::Bool` => true|false
-/// * `Value::Number` => the number, as formatted by `serde_json`.
+/// * `Value::Boolean` => true|false
+/// * `Value::Integer` => the integer
+/// * `Value::Float` => the float
 /// * `Value::String` => the string, HTML-escaped
 ///
 /// Arrays and objects are not formatted, and attempting to do so will result in a rendering error.
 pub fn format(value: &Value, output: &mut String) -> Result<()> {
     match value {
         Value::Null => Ok(()),
-        Value::Bool(b) => {
+        Value::Boolean(b) => {
             write!(output, "{}", b)?;
             Ok(())
         }
-        Value::Number(n) => {
-            write!(output, "{}", n)?;
+        Value::Integer(i) => {
+            write!(output, "{}", i)?;
+            Ok(())
+        }
+        Value::Float(f) => {
+            write!(output, "{}", f)?;
             Ok(())
         }
         Value::String(s) => {
@@ -147,12 +152,16 @@ pub fn format(value: &Value, output: &mut String) -> Result<()> {
 pub fn format_unescaped(value: &Value, output: &mut String) -> Result<()> {
     match value {
         Value::Null => Ok(()),
-        Value::Bool(b) => {
+        Value::Boolean(b) => {
             write!(output, "{}", b)?;
             Ok(())
         }
-        Value::Number(n) => {
-            write!(output, "{}", n)?;
+        Value::Integer(i) => {
+            write!(output, "{}", i)?;
+            Ok(())
+        }
+        Value::Float(f) => {
+            write!(output, "{}", f)?;
             Ok(())
         }
         Value::String(s) => {
@@ -208,12 +217,12 @@ impl<'template> TinyTemplate<'template> {
     }
 
     /// Render the template with the given name using the given context object. The context
-    /// object must implement `serde::Serialize` as it will be converted to `serde_json::Value`.
+    /// object must implement `serde::Serialize`.
     pub fn render<C>(&self, template: &str, context: &C) -> Result<String>
     where
         C: Serialize,
     {
-        let value = serde_json::to_value(context)?;
+        let value = Value::serialize_from(context)?;
         match self.templates.get(template) {
             Some(tmpl) => tmpl.render(
                 &value,
diff --git a/src/syntax.rs b/src/syntax.rs
@@ -2,9 +2,9 @@
 //!
 //! ### Context Types
 //!
-//! TinyTemplate uses `serde_json`'s Value structure to represent the context. Therefore, any
+//! TinyTemplate uses a internal `Value` structure to represent the context. Therefore, any
 //! `Serializable` structure can be used as a context. All values in such structures are mapped to
-//! their JSON representations - booleans, numbers, strings, arrays, objects and nulls.
+//! representations similar to JSON - booleans, integers, floats, strings, arrays, objects and nulls.
 //!
 //! ### Values
 //!
diff --git a/src/template.rs b/src/template.rs
@@ -4,10 +4,10 @@ use compiler::TemplateCompiler;
 use error::Error::*;
 use error::*;
 use instruction::{Instruction, PathSlice, PathStep};
-use serde_json::Value;
 use std::collections::HashMap;
 use std::fmt::Write;
 use std::slice;
+use value::Value;
 use ValueFormatter;
 
 /// Enum defining the different kinds of records on the context stack.
@@ -64,17 +64,23 @@ impl<'render, 'template> RenderContext<'render, 'template> {
         let mut current = object;
         for step in path.iter() {
             if let PathStep::Index(_, n) = step {
-                if let Some(next) = current.get(n) {
-                    current = next;
-                    continue;
+                if let Value::Array(array) = current {
+                    if let Some(next) = array.get(*n) {
+                        current = next;
+                        continue;
+                    }
                 }
             }
 
             let step: &str = &*step;
 
-            match current.get(step) {
-                Some(next) => current = next,
-                None => return Err(lookup_error(self.original_text, step, path, current)),
+            match &current {
+                Value::Object(map) => match map.get(step) {
+                    Some(next) => current = next,
+                    None => return Err(lookup_error(self.original_text, step, path, current)),
+                },
+
+                _ => return Err(lookup_error(self.original_text, step, path, current)),
             }
         }
         Ok(current)
@@ -222,12 +228,12 @@ impl<'template> Template<'template> {
                                 let (index, length) = render_context.lookup_index()?;
                                 index == (length - 1)
                             }
-                            "@root" => self.value_is_truthy(render_context.lookup_root()?, path)?,
+                            "@root" => self.value_is_truthy(render_context.lookup_root()?),
                             other => panic!("Unknown keyword {}", other), // This should have been caught by the parser.
                         }
                     } else {
                         let value_to_render = render_context.lookup(path)?;
-                        self.value_is_truthy(value_to_render, path)?
+                        self.value_is_truthy(value_to_render)
                     };
                     if *negate {
                         truthy = !truthy;
@@ -325,21 +331,16 @@ impl<'template> Template<'template> {
         Ok(())
     }
 
-    fn value_is_truthy(&self, value: &Value, path: PathSlice) -> Result<bool> {
-        let truthy = match value {
+    fn value_is_truthy(&self, value: &Value) -> bool {
+        match value {
             Value::Null => false,
-            Value::Bool(b) => *b,
-            Value::Number(n) => match n.as_f64() {
-                Some(float) => float != 0.0,
-                None => {
-                    return Err(truthiness_error(self.original_text, path));
-                }
-            },
+            Value::Boolean(b) => *b,
+            Value::Integer(i) => *i != 0,
+            Value::Float(f) => *f != 0.0,
             Value::String(s) => !s.is_empty(),
             Value::Array(arr) => !arr.is_empty(),
             Value::Object(_) => true,
-        };
-        Ok(truthy)
+        }
     }
 }
 
@@ -382,7 +383,8 @@ mod test {
             nested: NestedContext { value: 10 },
             escapes: "1:< 2:> 3:& 4:' 5:\"",
         };
-        ::serde_json::to_value(&ctx).unwrap()
+
+        Value::serialize_from(&ctx).unwrap()
     }
 
     fn other_templates() -> HashMap<&'static str, Template<'static>> {
@@ -807,7 +809,7 @@ mod test {
     fn test_root_print() {
         let template = compile("{ @root }");
         let context = "Hello World!";
-        let context = ::serde_json::to_value(&context).unwrap();
+        let context = Value::serialize_from(&context).unwrap();
         let template_registry = other_templates();
         let formatter_registry = formatters();
         let string = template
@@ -825,7 +827,7 @@ mod test {
     fn test_root_branch() {
         let template = compile("{{ if @root }}Hello World!{{ endif }}");
         let context = true;
-        let context = ::serde_json::to_value(&context).unwrap();
+        let context = Value::serialize_from(&context).unwrap();
         let template_registry = other_templates();
         let formatter_registry = formatters();
         let string = template
@@ -843,7 +845,7 @@ mod test {
     fn test_root_iterate() {
         let template = compile("{{ for a in @root }}{ a }{{ endfor }}");
         let context = vec!["foo", "bar"];
-        let context = ::serde_json::to_value(&context).unwrap();
+        let context = Value::serialize_from(&context).unwrap();
         let template_registry = other_templates();
         let formatter_registry = formatters();
         let string = template
@@ -861,7 +863,7 @@ mod test {
     fn test_number_truthiness_zero() {
         let template = compile("{{ if @root }}truthy{{else}}not truthy{{ endif }}");
         let context = 0;
-        let context = ::serde_json::to_value(&context).unwrap();
+        let context = Value::serialize_from(&context).unwrap();
         let template_registry = other_templates();
         let formatter_registry = formatters();
         let string = template
@@ -879,7 +881,7 @@ mod test {
     fn test_number_truthiness_one() {
         let template = compile("{{ if @root }}truthy{{else}}not truthy{{ endif }}");
         let context = 1;
-        let context = ::serde_json::to_value(&context).unwrap();
+        let context = Value::serialize_from(&context).unwrap();
         let template_registry = other_templates();
         let formatter_registry = formatters();
         let string = template
@@ -902,7 +904,7 @@ mod test {
 
         let template = compile("{ foo.1 }{ foo.0 }");
         let context = Context { foo: (123, 456) };
-        let context = ::serde_json::to_value(&context).unwrap();
+        let context = Value::serialize_from(&context).unwrap();
         let template_registry = other_templates();
         let formatter_registry = formatters();
         let string = template
@@ -928,7 +930,7 @@ mod test {
         foo.insert("0", 123);
         foo.insert("1", 456);
         let context = Context { foo };
-        let context = ::serde_json::to_value(&context).unwrap();
+        let context = Value::serialize_from(&context).unwrap();
         let template_registry = other_templates();
         let formatter_registry = formatters();
         let string = template
diff --git a/src/value.rs b/src/value.rs
