Remove thiserror dependency

It is convenient, but not worth adding an extra dependency.

Author: tomhoule

graphql_client_codegen/Cargo.toml

@@ -17,4 +17,3 @@ quote = "^1.0"
 serde_json = "1.0"
 serde = { version = "^1.0", features = ["derive"] }
 syn = "^1.0"
-thiserror = "1.0.10"

graphql_client_codegen/src/generated_module.rs

@@ -6,17 +6,23 @@ use crate::{
 use heck::*;
 use proc_macro2::{Ident, Span, TokenStream};
 use quote::quote;
-use thiserror::Error;
+use std::{error::Error, fmt::Display};
 
-#[derive(Debug, Error)]
-#[error(
-    "Could not find an operation named {} in the query document.",
-    operation_name
-)]
+#[derive(Debug)]
 struct OperationNotFound {
     operation_name: String,
 }
 
+impl Display for OperationNotFound {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.write_str("Could not find an operation named ")?;
+        f.write_str(&self.operation_name)?;
+        f.write_str(" in the query document.")
+    }
+}
+
+impl Error for OperationNotFound {}
+
 /// This struct contains the parameters necessary to generate code for a given operation.
 pub(crate) struct GeneratedModule<'a> {
     pub operation: &'a str,

graphql_client_codegen/src/lib.rs

@@ -29,13 +29,19 @@ mod tests;
 
 pub use crate::codegen_options::{CodegenMode, GraphQLClientCodegenOptions};
 
-use std::{collections::HashMap, io};
-use thiserror::Error;
+use std::{collections::HashMap, fmt::Display, io};
 
-#[derive(Debug, Error)]
-#[error("{0}")]
+#[derive(Debug)]
 struct GeneralError(String);
 
+impl Display for GeneralError {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.write_str(&self.0)
+    }
+}
+
+impl std::error::Error for GeneralError {}
+
 type BoxError = Box<dyn std::error::Error + Send + Sync + 'static>;
 type CacheMap<T> = std::sync::Mutex<HashMap<std::path::PathBuf, T>>;
 
@@ -137,24 +143,34 @@ pub fn generate_module_token_stream(
     Ok(modules)
 }
 
-#[derive(Debug, Error)]
+#[derive(Debug)]
 enum ReadFileError {
-    #[error(
-        "Could not find file with path: {}\
-        Hint: file paths in the GraphQLQuery attribute are relative to the project root (location of the Cargo.toml). Example: query_path = \"src/my_query.graphql\".",
-        path
-    )]
-    FileNotFound {
-        path: String,
-        #[source]
-        io_error: io::Error,
-    },
-    #[error("Error reading file at: {}", path)]
-    ReadError {
-        path: String,
-        #[source]
-        io_error: io::Error,
-    },
+    FileNotFound { path: String, io_error: io::Error },
+    ReadError { path: String, io_error: io::Error },
+}
+
+impl Display for ReadFileError {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            ReadFileError::FileNotFound { path, .. } => {
+                write!(f, "Could not find file with path: {}\
+                Hint: file paths in the GraphQLQuery attribute are relative to the project root (location of the Cargo.toml). Example: query_path = \"src/my_query.graphql\".", path)
+            }
+            ReadFileError::ReadError { path, .. } => {
+                f.write_str("Error reading file at: ")?;
+                f.write_str(path)
+            }
+        }
+    }
+}
+
+impl std::error::Error for ReadFileError {
+    fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
+        match self {
+            ReadFileError::FileNotFound { path: _, io_error } => Some(io_error),
+            ReadFileError::ReadError { path: _, io_error } => Some(io_error),
+        }
+    }
 }
 
 fn read_file(path: &std::path::Path) -> Result<String, ReadFileError> {

graphql_client_codegen/src/query.rs

@@ -18,15 +18,24 @@ use crate::{
         StoredInputType, StoredScalar, TypeId, UnionId,
     },
 };
-use std::collections::{HashMap, HashSet};
-use thiserror::Error;
+use std::{
+    collections::{HashMap, HashSet},
+    fmt::Display,
+};
 
-#[derive(Debug, Error)]
-#[error("{}", message)]
+#[derive(Debug)]
 pub(crate) struct QueryValidationError {
     message: String,
 }
 
+impl Display for QueryValidationError {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.write_str(&self.message)
+    }
+}
+
+impl std::error::Error for QueryValidationError {}
+
 impl QueryValidationError {
     pub(crate) fn new(message: String) -> Self {
         QueryValidationError { message }