Add Debug impls.

This commit makes the following changes

 - Add an opaque `Debug` impl for `Client`.
 - Add a rich `Debug` impl for `Row`.
 - Make the `Debug` impl for `Type` clearer.
 - Change the `Debug` for `Column` to be slightly neater.

postgres-types/src/lib.rs

@@ -207,9 +207,15 @@ mod special;
 mod type_gen;
 
 /// A Postgres type.
-#[derive(PartialEq, Eq, Clone, Debug, Hash)]
+#[derive(PartialEq, Eq, Clone, Hash)]
 pub struct Type(Inner);
 
+impl fmt::Debug for Type {
+    fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
+        fmt::Debug::fmt(&self.0, fmt)
+    }
+}
+
 impl fmt::Display for Type {
     fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
         match self.schema() {

tokio-postgres/src/client.rs

@@ -21,6 +21,7 @@ use futures::{future, pin_mut, ready, StreamExt, TryStreamExt};
 use parking_lot::Mutex;
 use postgres_protocol::message::backend::Message;
 use std::collections::HashMap;
+use std::fmt;
 use std::sync::Arc;
 use std::task::{Context, Poll};
 use std::time::Duration;
@@ -529,3 +530,9 @@ impl Client {
         self.inner.sender.is_closed()
     }
 }
+
+impl fmt::Debug for Client {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_struct("Client").finish()
+    }
+}

tokio-postgres/src/row.rs

@@ -100,6 +100,62 @@ pub struct Row {
     ranges: Vec<Option<Range<usize>>>,
 }
 
+/// A macro to map pg types to rust types, for debug display.
+macro_rules! debug_row_type {
+    ($this:expr; $map:expr; $idx:expr; $name:expr; $type:expr; $($pg_ty:tt => $ty:ty),*) => {
+        match $type {
+            $(
+                &Type::$pg_ty => match <$ty as FromSql>::from_sql_nullable(
+                    &Type::$pg_ty,
+                    $this.0.col_buffer($idx),
+                ) {
+                    Ok(val) => $map.entry(&$name, &val),
+                    Err(_) => $map.entry(&$name, &"<error>"),
+                },
+            )*
+            _ => $map.entry(&$name, &"<opaque type>"),
+        }
+    }
+}
+
+impl fmt::Debug for Row {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        // Provides debug impl for row contents.
+        struct RowData<'a>(&'a Row);
+
+        impl fmt::Debug for RowData<'_> {
+            fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+                let mut map = f.debug_map();
+                for (idx, col) in self.0.columns().iter().enumerate() {
+                    debug_row_type!(self; map; idx; col.name(); col.type_();
+                        BOOL => bool,
+                        INT2 => i16,
+                        INT4 => i32,
+                        INT8 => i64,
+                        FLOAT4 => f32,
+                        FLOAT8 => f64,
+                        VARCHAR => String,
+                        BPCHAR => String,
+                        TEXT => String,
+                        JSON => String,
+                        XML => String,
+                        TIMESTAMPTZ => std::time::SystemTime,
+                        TIMESTAMP => std::time::SystemTime,
+                        BYTEA => Vec<u8>
+                        // More types could be added here.
+                    );
+                }
+                map.finish()
+            }
+        }
+
+        f.debug_struct("Row")
+            .field("columns", &self.columns())
+            .field("data", &RowData(self))
+            .finish()
+    }
+}
+
 impl Row {
     pub(crate) fn new(statement: Statement, body: DataRowBody) -> Result<Row, Error> {
         let ranges = body.ranges().collect().map_err(Error::parse)?;
@@ -170,8 +226,13 @@ impl Row {
             ));
         }
 
-        let buf = self.ranges[idx].clone().map(|r| &self.body.buffer()[r]);
-        FromSql::from_sql_nullable(ty, buf).map_err(|e| Error::from_sql(e, idx))
+        FromSql::from_sql_nullable(ty, self.col_buffer(idx)).map_err(|e| Error::from_sql(e, idx))
+    }
+
+    /// Get the raw bytes for the column at the given index.
+    fn col_buffer(&self, idx: usize) -> Option<&[u8]> {
+        let range = self.ranges[idx].to_owned()?;
+        Some(&self.body.buffer()[range])
     }
 }
 

tokio-postgres/src/statement.rs

@@ -3,7 +3,10 @@ use crate::codec::FrontendMessage;
 use crate::connection::RequestMessages;
 use crate::types::Type;
 use postgres_protocol::message::frontend;
-use std::sync::{Arc, Weak};
+use std::{
+    fmt,
+    sync::{Arc, Weak},
+};
 
 struct StatementInner {
     client: Weak<InnerClient>,
@@ -62,7 +65,6 @@ impl Statement {
 }
 
 /// Information about a column of a query.
-#[derive(Debug)]
 pub struct Column {
     name: String,
     type_: Type,
@@ -83,3 +85,12 @@ impl Column {
         &self.type_
     }
 }
+
+impl fmt::Debug for Column {
+    fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
+        fmt.debug_struct("Column")
+            .field("name", &self.name)
+            .field("type", &self.type_)
+            .finish()
+    }
+}