If file logging is used, do not create the output file if no log is w…

…ritten

Resolves emabee#62

CHANGELOG.md

@@ -5,14 +5,19 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/) and this
 project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [0.15.13] - 2020-08-07
+
+If file logging is used, do not create the output file if no log is written
+Solves issue [issue-62](https://github.com/emabee/flexi_logger/issues/62).
+
 ## [0.15.12] - 2020-08-07
 
 Make `1.37.0` the minimal rust version for `flexi_logger`.
 
 ## [0.15.11] - 2020-08-07
 
 Introduce feature `specfile_without_notification` to allow coping with OS issues
-(see [issue-59](https://github.com/emabee/flexi_logger/issues/59)).
+(solves [issue-59](https://github.com/emabee/flexi_logger/issues/59)).
 
 ## [0.15.10] - 2020-07-22
 
@@ -21,16 +26,16 @@ Minor code maintenance.
 ## [0.15.9] - 2020-07-21
 
 Allow using the log target with fantasy names, like with `env_logger`.
-Closes [issue-56](https://github.com/emabee/flexi_logger/issues/56).
+Solves [issue-56](https://github.com/emabee/flexi_logger/issues/56).
 
 ## [0.15.8] - 2020-07-20
 
 Allow modifying the coloring palette through the environment variable `FLEXI_LOGGER_PALETTE`.
 See function [style](https://docs.rs/flexi_logger/latest/flexi_logger/fn.style.html) for details.
-Closes [issue-55](https://github.com/emabee/flexi_logger/issues/55).
+Solves [issue-55](https://github.com/emabee/flexi_logger/issues/55).
 
 By default, don't use colors if stdout or stderr are not a terminal
-([issue-57](https://github.com/emabee/flexi_logger/issues/57)).
+Solves [issue-57](https://github.com/emabee/flexi_logger/issues/57).
 
 Add variant Criterion::AgeOrSize
 (kudos to

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "flexi_logger"
-version = "0.15.13-alpha"
+version = "0.15.13"
 authors = ["emabee <[email protected]>"]
 edition = "2018"
 license = "MIT OR Apache-2.0"

src/lib.rs

@@ -44,6 +44,7 @@ mod flexi_logger;
 mod formats;
 mod log_specification;
 mod logger;
+mod parameters;
 mod primary_writer;
 mod reconfiguration_handle;
 
@@ -56,7 +57,8 @@ pub use crate::deferred_now::DeferredNow;
 pub use crate::flexi_error::FlexiLoggerError;
 pub use crate::formats::*;
 pub use crate::log_specification::{LogSpecBuilder, LogSpecification, ModuleFilter};
-pub use crate::logger::{Age, Cleanup, Criterion, Duplicate, LogTarget, Logger, Naming};
+pub use crate::logger::{Duplicate, LogTarget, Logger};
+pub use crate::parameters::{Age, Cleanup, Criterion, Naming};
 pub use crate::reconfiguration_handle::ReconfigurationHandle;
 
 /// Function type for Format functions.

src/logger.rs

@@ -1,9 +1,11 @@
 use crate::flexi_logger::FlexiLogger;
 use crate::primary_writer::PrimaryWriter;
 use crate::writers::{FileLogWriter, FileLogWriterBuilder, LogWriter};
-use crate::FormatFunction;
-use crate::ReconfigurationHandle;
-use crate::{formats, FlexiLoggerError, LogSpecification};
+use crate::{
+    formats, Cleanup, Criterion, FlexiLoggerError, FormatFunction, LogSpecification, Naming,
+    ReconfigurationHandle,
+};
+
 #[cfg(feature = "specfile")]
 use notify::{watcher, DebouncedEvent, RecursiveMode, Watcher};
 use std::collections::HashMap;
@@ -857,143 +859,6 @@ pub(crate) fn log_spec_string_from_file<P: AsRef<std::path::Path>>(
     Ok(buf)
 }
 
-/// Criterion when to rotate the log file.
-///
-/// Used in [`Logger::rotate`](struct.Logger.html#method.rotate).
-#[derive(Copy, Clone, Debug)]
-pub enum Criterion {
-    /// Rotate the log file when it exceeds the specified size in bytes.
-    Size(u64),
-    /// Rotate the log file when it has become older than the specified age.
-    ///
-    /// ## Minor limitation
-    ///
-    /// ### TL,DR
-    /// the combination of `Logger::append()`
-    /// with `Criterion::Age` works OK, but not perfectly correct on Windows or Linux
-    /// when the program is restarted.
-    ///
-    /// ### Details
-    /// Applying the age criterion works fine while your program is running.
-    /// Ideally, we should also apply it to the rCURRENT file when the program is restarted
-    /// and you chose the `Logger::append()` option.
-    ///
-    /// Unfortunately, this does not work on Windows, and it does not work on linux,
-    /// for different reasons.
-    ///
-    /// To minimize the impact on age-based file-rotation,
-    /// `flexi_logger` uses on Windows and linux its initialization time
-    /// rather than the real file property
-    /// as the created_at-info of an rCURRENT file that already exists, and the
-    /// current timestamp when file rotation happens during further execution.
-    /// Consequently, a left-over rCURRENT file from a previous program run will look newer
-    /// than it is, and will be used longer than it should be.
-    ///
-    /// #### Issue on Windows
-    ///
-    /// For compatibility with DOS (sic!), Windows magically transfers the created_at-info
-    /// of a file that is deleted (or renamed) to its successor,
-    /// when the recreation happens within some seconds [[1]](#ref-1).
-    ///
-    /// <a name="ref-1">[1]</a> [https://superuser.com/questions/966490/windows-7-what-is-date-created-file-property-referring-to](https://superuser.com/questions/966490/windows-7-what-is-date-created-file-property-referring-to).
-    ///
-    /// If the file property were used by `flexi_logger`,
-    /// the rCURRENT file would always appear to be as old as the
-    /// first one that ever was created - rotation by time would completely fail.
-    ///
-    /// #### Issue on Linux
-    ///
-    /// `std::fs::metadata.created()` returns `Err`, because linux does not maintain a
-    /// created-at-timestamp.
-    ///
-    Age(Age),
-    /// Rotate the file when it has either become older than the specified age, or when it has
-    /// exceeded the specified size in bytes.
-    ///
-    /// See documentation for Age and Size.
-    AgeOrSize(Age, u64),
-}
-
-/// The age after which a log file rotation will be triggered,
-/// when [`Criterion::Age`](enum.Criterion.html#variant.Age) is chosen.
-#[derive(Copy, Clone, Debug)]
-pub enum Age {
-    /// Rotate the log file when the local clock has started a new day since the
-    /// current file had been created.
-    Day,
-    /// Rotate the log file when the local clock has started a new hour since the
-    /// current file had been created.
-    Hour,
-    /// Rotate the log file when the local clock has started a new minute since the
-    /// current file had been created.
-    Minute,
-    /// Rotate the log file when the local clock has started a new second since the
-    /// current file had been created.
-    Second,
-}
-
-/// The naming convention for rotated log files.
-///
-/// With file rotation, the logs are written to a file with infix `_rCURRENT`.
-/// When rotation happens, the CURRENT log file will be renamed to a file with
-/// another infix of the form `"_r..."`. `Naming` defines which other infix will be used.
-///
-/// Used in [`Logger::rotate`](struct.Logger.html#method.rotate).
-#[derive(Copy, Clone, Debug)]
-pub enum Naming {
-    /// File rotation rotates to files with a timestamp-infix, like `"r2020-01-27_14-41-08"`.
-    Timestamps,
-    /// File rotation rotates to files with a number-infix.
-    Numbers,
-}
-
-/// Defines the strategy for handling older log files.
-///
-/// Is used in [`Logger::rotate`](struct.Logger.html#method.rotate).
-///
-/// Note that if you use a strategy other than `Cleanup::Never`, then the cleanup work is
-/// by default done in an extra thread, to minimize the impact on the program.
-/// See
-/// [`Logger::cleanup_in_background_thread`](struct.Logger.html#method.cleanup_in_background_thread)
-/// if you want to control whether this extra thread is created and used.
-#[derive(Copy, Clone, Debug)]
-pub enum Cleanup {
-    /// Older log files are not touched - they remain for ever.
-    Never,
-    /// The specified number of rotated log files are kept.
-    /// Older files are deleted, if necessary.
-    KeepLogFiles(usize),
-    /// The specified number of rotated log files are zipped and kept.
-    /// Older files are deleted, if necessary.
-    ///
-    /// This option is only available with feature `ziplogs`.
-    #[cfg(feature = "ziplogs")]
-    KeepZipFiles(usize),
-    /// Allows keeping some files as text files and some as zip files.
-    ///
-    /// Is used in
-    ///
-    /// ## Example
-    ///
-    /// `KeepLogAndZipFiles(5,30)` ensures that the youngest five log files are kept as text files,
-    /// the next 30 are kept as zip files, and older files are removed.
-    ///
-    /// This option is only available with feature `ziplogs`.
-    #[cfg(feature = "ziplogs")]
-    KeepLogAndZipFiles(usize, usize),
-}
-
-impl Cleanup {
-    // Returns true if some cleanup is to be done.
-    #[must_use]
-    pub(crate) fn do_cleanup(&self) -> bool {
-        match self {
-            Self::Never => false,
-            _ => true,
-        }
-    }
-}
-
 /// Used to control which messages are to be duplicated to stderr, when `log_to_file()` is used.
 #[derive(Debug)]
 pub enum Duplicate {

src/parameters.rs

@@ -0,0 +1,135 @@
+/// Criterion when to rotate the log file.
+///
+/// Used in [`Logger::rotate`](struct.Logger.html#method.rotate).
+#[derive(Copy, Clone, Debug)]
+pub enum Criterion {
+    /// Rotate the log file when it exceeds the specified size in bytes.
+    Size(u64),
+    /// Rotate the log file when it has become older than the specified age.
+    ///
+    /// ## Minor limitation
+    ///
+    /// ### TL,DR
+    /// the combination of `Logger::append()`
+    /// with `Criterion::Age` works OK, but not perfectly correct on Windows or Linux
+    /// when the program is restarted.
+    ///
+    /// ### Details
+    /// Applying the age criterion works fine while your program is running.
+    /// Ideally, we should also apply it to the rCURRENT file when the program is restarted
+    /// and you chose the `Logger::append()` option.
+    ///
+    /// Unfortunately, this does not work on Windows, and it does not work on linux,
+    /// for different reasons.
+    ///
+    /// To minimize the impact on age-based file-rotation,
+    /// `flexi_logger` uses on Windows and linux its initialization time
+    /// rather than the real file property
+    /// as the created_at-info of an rCURRENT file that already exists, and the
+    /// current timestamp when file rotation happens during further execution.
+    /// Consequently, a left-over rCURRENT file from a previous program run will look newer
+    /// than it is, and will be used longer than it should be.
+    ///
+    /// #### Issue on Windows
+    ///
+    /// For compatibility with DOS (sic!), Windows magically transfers the created_at-info
+    /// of a file that is deleted (or renamed) to its successor,
+    /// when the recreation happens within some seconds [[1]](#ref-1).
+    ///
+    /// <a name="ref-1">[1]</a> [https://superuser.com/questions/966490/windows-7-what-is-date-created-file-property-referring-to](https://superuser.com/questions/966490/windows-7-what-is-date-created-file-property-referring-to).
+    ///
+    /// If the file property were used by `flexi_logger`,
+    /// the rCURRENT file would always appear to be as old as the
+    /// first one that ever was created - rotation by time would completely fail.
+    ///
+    /// #### Issue on Linux
+    ///
+    /// `std::fs::metadata.created()` returns `Err`, because linux does not maintain a
+    /// created-at-timestamp.
+    ///
+    Age(Age),
+    /// Rotate the file when it has either become older than the specified age, or when it has
+    /// exceeded the specified size in bytes.
+    ///
+    /// See documentation for Age and Size.
+    AgeOrSize(Age, u64),
+}
+
+/// The age after which a log file rotation will be triggered,
+/// when [`Criterion::Age`](enum.Criterion.html#variant.Age) is chosen.
+#[derive(Copy, Clone, Debug)]
+pub enum Age {
+    /// Rotate the log file when the local clock has started a new day since the
+    /// current file had been created.
+    Day,
+    /// Rotate the log file when the local clock has started a new hour since the
+    /// current file had been created.
+    Hour,
+    /// Rotate the log file when the local clock has started a new minute since the
+    /// current file had been created.
+    Minute,
+    /// Rotate the log file when the local clock has started a new second since the
+    /// current file had been created.
+    Second,
+}
+
+/// The naming convention for rotated log files.
+///
+/// With file rotation, the logs are written to a file with infix `_rCURRENT`.
+/// When rotation happens, the CURRENT log file will be renamed to a file with
+/// another infix of the form `"_r..."`. `Naming` defines which other infix will be used.
+///
+/// Used in [`Logger::rotate`](struct.Logger.html#method.rotate).
+#[derive(Copy, Clone, Debug)]
+pub enum Naming {
+    /// File rotation rotates to files with a timestamp-infix, like `"r2020-01-27_14-41-08"`.
+    Timestamps,
+    /// File rotation rotates to files with a number-infix.
+    Numbers,
+}
+/// Defines the strategy for handling older log files.
+///
+/// Is used in [`Logger::rotate`](struct.Logger.html#method.rotate).
+///
+/// Note that if you use a strategy other than `Cleanup::Never`, then the cleanup work is
+/// by default done in an extra thread, to minimize the impact on the program.
+/// See
+/// [`Logger::cleanup_in_background_thread`](struct.Logger.html#method.cleanup_in_background_thread)
+/// if you want to control whether this extra thread is created and used.
+#[derive(Copy, Clone, Debug)]
+pub enum Cleanup {
+    /// Older log files are not touched - they remain for ever.
+    Never,
+    /// The specified number of rotated log files are kept.
+    /// Older files are deleted, if necessary.
+    KeepLogFiles(usize),
+    /// The specified number of rotated log files are zipped and kept.
+    /// Older files are deleted, if necessary.
+    ///
+    /// This option is only available with feature `ziplogs`.
+    #[cfg(feature = "ziplogs")]
+    KeepZipFiles(usize),
+    /// Allows keeping some files as text files and some as zip files.
+    ///
+    /// Is used in
+    ///
+    /// ## Example
+    ///
+    /// `KeepLogAndZipFiles(5,30)` ensures that the youngest five log files are kept as text files,
+    /// the next 30 are kept as zip files, and older files are removed.
+    ///
+    /// This option is only available with feature `ziplogs`.
+    #[cfg(feature = "ziplogs")]
+    KeepLogAndZipFiles(usize, usize),
+}
+
+impl Cleanup {
+    // Returns true if some cleanup is to be done.
+    #[must_use]
+    pub(crate) fn do_cleanup(&self) -> bool {
+        match self {
+            Self::Never => false,
+            _ => true,
+        }
+    }
+}