Enable nullable annotations (#803)

* Enable nullable annotations

* Remove unused Jetbrain annotations

* Ensure system using statements are first

* Improve nullability annotations

* Annotate encryptionDictionary is non-null when IsEncrypted is true

* Disable nullable for PdfTokenScanner.Get

* Improve nullability annotations for ObjectLocationProvider.TryGetCached

* Revert changes to RGBWorkingSpace

* Update UglyToad.PdfPig.Package with new framework targets (fixes nightly builds)

src/UglyToad.PdfPig/AcroForms/AcroForm.cs

@@ -6,7 +6,6 @@
     using Core;
     using Fields;
     using Tokens;
-    using Util.JetBrains.Annotations;
 
     /// <summary>
     /// A collection of interactive fields for gathering data from a user through dropdowns, textboxes, checkboxes, etc.
@@ -22,7 +21,6 @@ public class AcroForm
         /// <summary>
         /// The raw PDF dictionary which is the root form object.
         /// </summary>
-        [NotNull]
         public DictionaryToken Dictionary { get; }
 
         /// <summary>

src/UglyToad.PdfPig/AcroForms/AcroFormExtensions.cs

@@ -42,12 +42,12 @@ public static IEnumerable<AcroFieldBase> GetFields(this AcroFieldBase fieldBase)
         /// <summary>
         /// Get string values of field.
         /// </summary>
-        public static KeyValuePair<string, string> GetFieldValue(this AcroFieldBase fieldBase)
+        public static KeyValuePair<string?, string?> GetFieldValue(this AcroFieldBase fieldBase)
         {
             return fieldBase switch
             {
                 AcroTextField textField => new(textField.Information.PartialName, textField.Value),
-                AcroCheckboxField checkboxField => new(checkboxField.Information.PartialName, checkboxField.IsChecked.ToString()),
+                AcroCheckboxField checkboxField => new(checkboxField.Information.PartialName, checkboxField.IsChecked.ToString())!,
                 _ => new(fieldBase.Information.PartialName, ""),
             };
         }

src/UglyToad.PdfPig/AcroForms/Fields/AcroChoiceOption.cs

@@ -23,7 +23,7 @@ public class AcroChoiceOption
         /// <summary>
         /// The value of the option when the form is exported.
         /// </summary>
-        public string ExportValue { get; }
+        public string? ExportValue { get; }
 
         /// <summary>
         /// Whether the field defined an export value for this option.
@@ -33,7 +33,7 @@ public class AcroChoiceOption
         /// <summary>
         /// Create a new <see cref="AcroChoiceOption"/>.
         /// </summary>
-        public AcroChoiceOption(int index, bool isSelected, string name, string exportValue = null)
+        public AcroChoiceOption(int index, bool isSelected, string name, string? exportValue = null)
         {
             Index = index;
             IsSelected = isSelected;

src/UglyToad.PdfPig/AcroForms/Fields/AcroComboBoxField.cs

@@ -4,7 +4,6 @@
     using System.Collections.Generic;
     using Core;
     using Tokens;
-    using Util.JetBrains.Annotations;
 
     /// <inheritdoc />
     /// <summary>
@@ -21,20 +20,17 @@ public class AcroComboBoxField : AcroFieldBase
         /// <summary>
         /// The options to be presented to the user.
         /// </summary>
-        [NotNull]
         public IReadOnlyList<AcroChoiceOption> Options { get; }
 
         /// <summary>
         /// The names of any currently selected options.
         /// </summary>
-        [NotNull]
         public IReadOnlyList<string> SelectedOptions { get; }
 
         /// <summary>
         /// For multiple select lists with duplicate names gives the indices of the selected options.
         /// </summary>
-        [CanBeNull]
-        public IReadOnlyList<int> SelectedOptionIndices { get; }
+        public IReadOnlyList<int>? SelectedOptionIndices { get; }
 
         /// <inheritdoc />
         /// <summary>
@@ -49,10 +45,13 @@ public class AcroComboBoxField : AcroFieldBase
         /// <param name="selectedOptions">The names of the selected options.</param>
         /// <param name="pageNumber">The number of the page this field appears on.</param>
         /// <param name="bounds">The location of this field on the page.</param>
-        public AcroComboBoxField(DictionaryToken dictionary, string fieldType, AcroChoiceFieldFlags fieldFlags,
+        public AcroComboBoxField(
+            DictionaryToken dictionary,
+            string fieldType, 
+            AcroChoiceFieldFlags fieldFlags,
             AcroFieldCommonInformation information, IReadOnlyList<AcroChoiceOption> options, 
             IReadOnlyList<string> selectedOptions, 
-            IReadOnlyList<int> selectedOptionIndices,
+            IReadOnlyList<int>? selectedOptionIndices,
             int? pageNumber,
             PdfRectangle? bounds) :
             base(dictionary, fieldType, (uint)fieldFlags, AcroFieldType.ComboBox, information,

src/UglyToad.PdfPig/AcroForms/Fields/AcroFieldBase.cs

@@ -1,9 +1,8 @@
 namespace UglyToad.PdfPig.AcroForms.Fields
 {
-    using System;
     using Core;
+    using System;
     using Tokens;
-    using Util.JetBrains.Annotations;
 
     /// <summary>
     /// A field in an interactive <see cref="AcroForm"/>.
@@ -13,13 +12,11 @@ public abstract class AcroFieldBase
         /// <summary>
         /// The raw PDF dictionary for this field.
         /// </summary>
-        [NotNull]
         public DictionaryToken Dictionary { get; }
 
         /// <summary>
         /// The <see cref="string"/> representing the type of this field in PDF format.
         /// </summary>
-        [NotNull]
         public string RawFieldType { get; }
 
         /// <summary>
@@ -35,7 +32,6 @@ public abstract class AcroFieldBase
         /// <summary>
         /// The optional information common to all types of field.
         /// </summary>
-        [NotNull]
         public AcroFieldCommonInformation Information { get; }
 
         /// <summary>

src/UglyToad.PdfPig/AcroForms/Fields/AcroFieldCommonInformation.cs

@@ -1,7 +1,6 @@
 namespace UglyToad.PdfPig.AcroForms.Fields
 {
     using Core;
-    using Util.JetBrains.Annotations;
 
     /// <summary>
     /// Information from the field dictionary which is common across all field types.
@@ -18,26 +17,23 @@ public class AcroFieldCommonInformation
         /// The partial field name for this field. The fully qualified field name is the
         /// period '.' joined name of all parents' partial names and this field's partial name.
         /// </summary>
-        [CanBeNull]
-        public string PartialName { get; }
+        public string? PartialName { get; }
 
         /// <summary>
         /// The alternate field name to be used instead of the fully qualified field name where
         /// the field is being identified on the user interface or by screen readers.
         /// </summary>
-        [CanBeNull]
-        public string AlternateName { get; }
+        public string? AlternateName { get; }
 
         /// <summary>
         /// The mapping name used when exporting form field data from the document.
         /// </summary>
-        [CanBeNull]
-        public string MappingName { get; }
+        public string? MappingName { get; }
 
         /// <summary>
         /// Create a new <see cref="AcroFieldCommonInformation"/>.
         /// </summary>
-        public AcroFieldCommonInformation(IndirectReference? parent, string partialName, string alternateName, string mappingName)
+        public AcroFieldCommonInformation(IndirectReference? parent, string? partialName, string? alternateName, string? mappingName)
         {
             Parent = parent;
             PartialName = partialName;
@@ -48,7 +44,7 @@ public AcroFieldCommonInformation(IndirectReference? parent, string partialName,
         /// <inheritdoc />
         public override string ToString()
         {
-            string AppendIfNotNull(string val, string label, string result)
+            string AppendIfNotNull(string? val, string label, string result)
             {
                 if (val is null)
                 {

src/UglyToad.PdfPig/AcroForms/Fields/AcroListBoxField.cs

@@ -4,7 +4,6 @@
     using System.Collections.Generic;
     using Core;
     using Tokens;
-    using Util.JetBrains.Annotations;
 
     /// <inheritdoc />
     /// <summary>
@@ -20,20 +19,17 @@ public class AcroListBoxField : AcroFieldBase
         /// <summary>
         /// The options to be presented to the user.
         /// </summary>
-        [NotNull]
         public IReadOnlyList<AcroChoiceOption> Options { get; }
 
         /// <summary>
         /// The names of any currently selected options.
         /// </summary>
-        [NotNull]
         public IReadOnlyList<string> SelectedOptions { get; }
 
         /// <summary>
         /// For multiple select lists with duplicate names gives the indices of the selected options.
         /// </summary>
-        [CanBeNull]
-        public IReadOnlyList<int> SelectedOptionIndices { get; }
+        public IReadOnlyList<int>? SelectedOptionIndices { get; }
 
         /// <summary>
         /// For scrollable list boxes gives the index of the first visible option.
@@ -62,7 +58,7 @@ public class AcroListBoxField : AcroFieldBase
         public AcroListBoxField(DictionaryToken dictionary, string fieldType, AcroChoiceFieldFlags fieldFlags,
             AcroFieldCommonInformation information, IReadOnlyList<AcroChoiceOption> options,
             IReadOnlyList<string> selectedOptions, 
-            IReadOnlyList<int> selectedOptionIndices,
+            IReadOnlyList<int>? selectedOptionIndices,
             int? topIndex,
             int? pageNumber,
             PdfRectangle? bounds) : 

src/UglyToad.PdfPig/AcroForms/Fields/AcroTextField.cs

@@ -19,7 +19,7 @@ public class AcroTextField : AcroFieldBase
         /// The value of the text in this text field.
         /// This can be <see langword="null"/> if no value has been set.
         /// </summary>
-        public string Value { get; }
+        public string? Value { get; }
 
         /// <summary>
         /// The optional maximum length of the text field.
@@ -50,7 +50,7 @@ public class AcroTextField : AcroFieldBase
         /// <param name="bounds">The location of this field on the page.</param>
         public AcroTextField(DictionaryToken dictionary, string fieldType, AcroTextFieldFlags fieldFlags,
             AcroFieldCommonInformation information, 
-            string value,
+            string? value,
             int? maxLength,
             int? pageNumber,
             PdfRectangle? bounds) : 

src/UglyToad.PdfPig/Actions/ActionProvider.cs

@@ -1,32 +1,33 @@
 namespace UglyToad.PdfPig.Actions
 {
+    using System.Diagnostics.CodeAnalysis;
     using Core;
     using Logging;
-    using Outline;
+    using Outline.Destinations;
     using Tokenization.Scanner;
     using Tokens;
-    using Outline.Destinations;
     using Util;
 
     internal static class ActionProvider
     {
         /// <summary>
         /// Get an action (A) from dictionary. If GoTo, GoToR or GoToE, also fetches the action destination.
         /// </summary>
-        internal static bool TryGetAction(DictionaryToken dictionary,
+        internal static bool TryGetAction(
+            DictionaryToken dictionary,
             NamedDestinations namedDestinations,
             IPdfTokenScanner pdfScanner,
             ILog log,
-            out PdfAction result)
+            [NotNullWhen(true)] out PdfAction? result)
         {
             result = null;
 
-            if (!dictionary.TryGet(NameToken.A, pdfScanner, out DictionaryToken actionDictionary))
+            if (!dictionary.TryGet(NameToken.A, pdfScanner, out DictionaryToken? actionDictionary))
             {
                 return false;
             }
 
-            if (!actionDictionary.TryGet(NameToken.S, pdfScanner, out NameToken actionType))
+            if (!actionDictionary.TryGet(NameToken.S, pdfScanner, out NameToken? actionType))
             {
                 throw new PdfDocumentFormatException($"No action type (/S) specified for action: {actionDictionary}.");
             }
@@ -81,7 +82,7 @@ internal static bool TryGetAction(DictionaryToken dictionary,
                         fileSpecification = null;
                     }
 
-                    result = new GoToEAction(destination, fileSpecification);
+                    result = new GoToEAction(destination, fileSpecification!);
                     return true;
                 }
             }

src/UglyToad.PdfPig/Actions/UriAction.cs

@@ -1,4 +1,6 @@
-namespace UglyToad.PdfPig.Actions
+#nullable disable
+
+namespace UglyToad.PdfPig.Actions
 {
     /// <summary>
     /// Action to open a URI

src/UglyToad.PdfPig/AdvancedPdfDocumentAccess.cs

@@ -2,6 +2,7 @@
 {
     using System;
     using System.Collections.Generic;
+    using System.Diagnostics.CodeAnalysis;
     using Content;
     using Core;
     using Filters;
@@ -37,14 +38,14 @@ internal AdvancedPdfDocumentAccess(IPdfTokenScanner pdfScanner,
         /// </summary>
         /// <param name="embeddedFiles">The set of embedded files in this document.</param>
         /// <returns><see langword="true"/> if this document contains more than zero embedded files, otherwise <see langword="false"/>.</returns>
-        public bool TryGetEmbeddedFiles(out IReadOnlyList<EmbeddedFile> embeddedFiles)
+        public bool TryGetEmbeddedFiles([NotNullWhen(true)] out IReadOnlyList<EmbeddedFile>? embeddedFiles)
         {
             GuardDisposed();
 
             embeddedFiles = null;
 
-            if (!catalog.CatalogDictionary.TryGet(NameToken.Names, pdfScanner, out DictionaryToken namesDictionary)
-                || !namesDictionary.TryGet(NameToken.EmbeddedFiles, pdfScanner, out DictionaryToken embeddedFileNamesDictionary))
+            if (!catalog.CatalogDictionary.TryGet(NameToken.Names, pdfScanner, out DictionaryToken? namesDictionary)
+                || !namesDictionary.TryGet(NameToken.EmbeddedFiles, pdfScanner, out DictionaryToken? embeddedFileNamesDictionary))
             {
                 return false;
             }
@@ -60,15 +61,15 @@ public bool TryGetEmbeddedFiles(out IReadOnlyList<EmbeddedFile> embeddedFiles)
 
             foreach (var keyValuePair in embeddedFileNames)
             {
-                if (!DirectObjectFinder.TryGet(keyValuePair.Value, pdfScanner, out DictionaryToken fileDescriptorDictionaryToken)
-                    || !fileDescriptorDictionaryToken.TryGet(NameToken.Ef, pdfScanner, out DictionaryToken efDictionary)
-                    || !efDictionary.TryGet(NameToken.F, pdfScanner, out StreamToken fileStreamToken))
+                if (!DirectObjectFinder.TryGet(keyValuePair.Value, pdfScanner, out DictionaryToken? fileDescriptorDictionaryToken)
+                    || !fileDescriptorDictionaryToken.TryGet(NameToken.Ef, pdfScanner, out DictionaryToken? efDictionary)
+                    || !efDictionary.TryGet(NameToken.F, pdfScanner, out StreamToken? fileStreamToken))
                 {
                     continue;
                 }
 
                 var fileSpecification = string.Empty;
-                if (fileDescriptorDictionaryToken.TryGet(NameToken.F, pdfScanner, out IDataToken<string> fileSpecificationToken))
+                if (fileDescriptorDictionaryToken.TryGet(NameToken.F, pdfScanner, out IDataToken<string>? fileSpecificationToken))
                 {
                     fileSpecification = fileSpecificationToken.Data;
                 }