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Introduce Strings.lenientFormat(), copied from Preconditions.format()…
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…. Rewrote documentation but the method body remains unchanged.

RELNOTES=Introduce `Strings.lenientFormat()`, copied from `Preconditions.format()`.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=196586088
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@dimo414 @ronshapiro
dimo414 authored and ronshapiro committed May 15, 2018
1 parent 9b4a9db commit 7fe1702
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19 changes: 19 additions & 0 deletions android/guava-tests/test/com/google/common/base/StringsTest.java
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Original file line number Diff line number Diff line change
Expand Up @@ -211,6 +211,25 @@ public void testValidSurrogatePairAt() {
assertFalse(Strings.validSurrogatePairAt("\uD8ABx", 0));
}

public void testLenientFormat() {
assertEquals("%s", Strings.lenientFormat("%s"));
assertEquals("5", Strings.lenientFormat("%s", 5));
assertEquals("foo [5]", Strings.lenientFormat("foo", 5));
assertEquals("foo [5, 6, 7]", Strings.lenientFormat("foo", 5, 6, 7));
assertEquals("%s 1 2", Strings.lenientFormat("%s %s %s", "%s", 1, 2));
assertEquals(" [5, 6]", Strings.lenientFormat("", 5, 6));
assertEquals("123", Strings.lenientFormat("%s%s%s", 1, 2, 3));
assertEquals("1%s%s", Strings.lenientFormat("%s%s%s", 1));
assertEquals("5 + 6 = 11", Strings.lenientFormat("%s + 6 = 11", 5));
assertEquals("5 + 6 = 11", Strings.lenientFormat("5 + %s = 11", 6));
assertEquals("5 + 6 = 11", Strings.lenientFormat("5 + 6 = %s", 11));
assertEquals("5 + 6 = 11", Strings.lenientFormat("%s + %s = %s", 5, 6, 11));
assertEquals("null [null, null]", Strings.lenientFormat("%s", null, null, null));
assertEquals("null [5, 6]", Strings.lenientFormat(null, 5, 6));
assertEquals("null", Strings.lenientFormat("%s", (Object) null));
assertEquals("(Object[])null", Strings.lenientFormat("%s", (Object[]) null));
}

@GwtIncompatible // NullPointerTester
public void testNullPointers() {
NullPointerTester tester = new NullPointerTester();
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66 changes: 66 additions & 0 deletions android/guava/src/com/google/common/base/Strings.java
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Original file line number Diff line number Diff line change
Expand Up @@ -210,6 +210,72 @@ public static String commonSuffix(CharSequence a, CharSequence b) {
return a.subSequence(a.length() - s, a.length()).toString();
}

/**
* Returns the given {@code template} string with each occurrence of {@code "%s"} replaced with
* the corresponding argument value from {@code args}; or, if the placeholder and argument counts
* do not match, returns a best-effort form of that string. Will not throw an exception under any
* circumstances (as long as all arguments' {@code toString} methods successfully return).
*
* <p><b>Note:</b> For most string-formatting needs, use {@link String#format}, {@link
* PrintWriter#format}, and related methods. These support the full range of {@linkplain
* Formatter#syntax format specifiers}, and alert you to usage errors by throwing {@link
* InvalidFormatException}.
*
* <p>In certain cases, such as outputting debugging information or constructing a message to be
* used for another unchecked exception, an exception during string formatting would serve little
* purpose except to supplant the real information you were trying to provide. These are the cases
* this method is made for; it instead generates a best-effort string with all supplied argument
* values present. This method is also useful in environments such as GWT where {@code
* String.format} is not available. As an example, method implementations of the {@link
* Preconditions} class use this formatter, for both of the reasons just discussed.
*
* <p><b>Warning:</b> Only the exact two-character placeholder sequence {@code "%s"} is
* recognized.
*
* @param template a string containing zero or more {@code "%s"} placeholder sequences. {@code
* null} is treated as the four-character string {@code "null"}.
* @param args the arguments to be substituted into the message template. The first argument
* specified is substituted for the first occurrence of {@code "%s"} in the template, and so
* forth. A {@code null} argument is converted to the four-character string {@code "null"};
* non-null values are converted to strings using {@link Object#toString()}.
* @since NEXT
*/
// TODO(diamondm) consider using Arrays.toString() for array parameters
// TODO(diamondm) capture exceptions thrown from arguments' toString methods
public static String lenientFormat(@NullableDecl String template, @NullableDecl Object... args) {
template = String.valueOf(template); // null -> "null"

args = args == null ? new Object[] {"(Object[])null"} : args;

// start substituting the arguments into the '%s' placeholders
StringBuilder builder = new StringBuilder(template.length() + 16 * args.length);
int templateStart = 0;
int i = 0;
while (i < args.length) {
int placeholderStart = template.indexOf("%s", templateStart);
if (placeholderStart == -1) {
break;
}
builder.append(template, templateStart, placeholderStart);
builder.append(args[i++]);
templateStart = placeholderStart + 2;
}
builder.append(template, templateStart, template.length());

// if we run out of placeholders, append the extra args in square braces
if (i < args.length) {
builder.append(" [");
builder.append(args[i++]);
while (i < args.length) {
builder.append(", ");
builder.append(args[i++]);
}
builder.append(']');
}

return builder.toString();
}

/**
* True when a valid surrogate pair starts at the given {@code index} in the given {@code string}.
* Out-of-range indexes return false.
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5 changes: 5 additions & 0 deletions guava-gwt/test/com/google/common/base/StringsTest_gwt.java
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Original file line number Diff line number Diff line change
Expand Up @@ -38,6 +38,11 @@ public void testIsNullOrEmpty() throws Exception {
testCase.testIsNullOrEmpty();
}

public void testLenientFormat() throws Exception {
com.google.common.base.StringsTest testCase = new com.google.common.base.StringsTest();
testCase.testLenientFormat();
}

public void testNullToEmpty() throws Exception {
com.google.common.base.StringsTest testCase = new com.google.common.base.StringsTest();
testCase.testNullToEmpty();
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19 changes: 19 additions & 0 deletions guava-tests/test/com/google/common/base/StringsTest.java
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Original file line number Diff line number Diff line change
Expand Up @@ -211,6 +211,25 @@ public void testValidSurrogatePairAt() {
assertFalse(Strings.validSurrogatePairAt("\uD8ABx", 0));
}

public void testLenientFormat() {
assertEquals("%s", Strings.lenientFormat("%s"));
assertEquals("5", Strings.lenientFormat("%s", 5));
assertEquals("foo [5]", Strings.lenientFormat("foo", 5));
assertEquals("foo [5, 6, 7]", Strings.lenientFormat("foo", 5, 6, 7));
assertEquals("%s 1 2", Strings.lenientFormat("%s %s %s", "%s", 1, 2));
assertEquals(" [5, 6]", Strings.lenientFormat("", 5, 6));
assertEquals("123", Strings.lenientFormat("%s%s%s", 1, 2, 3));
assertEquals("1%s%s", Strings.lenientFormat("%s%s%s", 1));
assertEquals("5 + 6 = 11", Strings.lenientFormat("%s + 6 = 11", 5));
assertEquals("5 + 6 = 11", Strings.lenientFormat("5 + %s = 11", 6));
assertEquals("5 + 6 = 11", Strings.lenientFormat("5 + 6 = %s", 11));
assertEquals("5 + 6 = 11", Strings.lenientFormat("%s + %s = %s", 5, 6, 11));
assertEquals("null [null, null]", Strings.lenientFormat("%s", null, null, null));
assertEquals("null [5, 6]", Strings.lenientFormat(null, 5, 6));
assertEquals("null", Strings.lenientFormat("%s", (Object) null));
assertEquals("(Object[])null", Strings.lenientFormat("%s", (Object[]) null));
}

@GwtIncompatible // NullPointerTester
public void testNullPointers() {
NullPointerTester tester = new NullPointerTester();
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67 changes: 67 additions & 0 deletions guava/src/com/google/common/base/Strings.java
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Original file line number Diff line number Diff line change
Expand Up @@ -209,6 +209,73 @@ public static String commonSuffix(CharSequence a, CharSequence b) {
return a.subSequence(a.length() - s, a.length()).toString();
}

/**
* Returns the given {@code template} string with each occurrence of {@code "%s"} replaced with
* the corresponding argument value from {@code args}; or, if the placeholder and argument counts
* do not match, returns a best-effort form of that string. Will not throw an exception under any
* circumstances (as long as all arguments' {@code toString} methods successfully return).
*
* <p><b>Note:</b> For most string-formatting needs, use {@link String#format}, {@link
* PrintWriter#format}, and related methods. These support the full range of {@linkplain
* Formatter#syntax format specifiers}, and alert you to usage errors by throwing {@link
* InvalidFormatException}.
*
* <p>In certain cases, such as outputting debugging information or constructing a message to be
* used for another unchecked exception, an exception during string formatting would serve little
* purpose except to supplant the real information you were trying to provide. These are the cases
* this method is made for; it instead generates a best-effort string with all supplied argument
* values present. This method is also useful in environments such as GWT where {@code
* String.format} is not available. As an example, method implementations of the {@link
* Preconditions} class use this formatter, for both of the reasons just discussed.
*
* <p><b>Warning:</b> Only the exact two-character placeholder sequence {@code "%s"} is
* recognized.
*
* @param template a string containing zero or more {@code "%s"} placeholder sequences. {@code
* null} is treated as the four-character string {@code "null"}.
* @param args the arguments to be substituted into the message template. The first argument
* specified is substituted for the first occurrence of {@code "%s"} in the template, and so
* forth. A {@code null} argument is converted to the four-character string {@code "null"};
* non-null values are converted to strings using {@link Object#toString()}.
* @since NEXT
*/
// TODO(diamondm) consider using Arrays.toString() for array parameters
// TODO(diamondm) capture exceptions thrown from arguments' toString methods
public static String lenientFormat(
@Nullable String template, @Nullable Object @Nullable... args) {
template = String.valueOf(template); // null -> "null"

args = args == null ? new Object[] {"(Object[])null"} : args;

// start substituting the arguments into the '%s' placeholders
StringBuilder builder = new StringBuilder(template.length() + 16 * args.length);
int templateStart = 0;
int i = 0;
while (i < args.length) {
int placeholderStart = template.indexOf("%s", templateStart);
if (placeholderStart == -1) {
break;
}
builder.append(template, templateStart, placeholderStart);
builder.append(args[i++]);
templateStart = placeholderStart + 2;
}
builder.append(template, templateStart, template.length());

// if we run out of placeholders, append the extra args in square braces
if (i < args.length) {
builder.append(" [");
builder.append(args[i++]);
while (i < args.length) {
builder.append(", ");
builder.append(args[i++]);
}
builder.append(']');
}

return builder.toString();
}

/**
* True when a valid surrogate pair starts at the given {@code index} in the given {@code string}.
* Out-of-range indexes return false.
Expand Down

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